Linear Technology Analog Devices LT8607B, Analog Devices LT8607 Datasheet

42V, 750mA Synchronous

0.1µF

4.7µF

1µF

22µF
X7R
1206

10pF

4.7µH

18.2k

1M

187k

100k

10nF

V

IN

EN/UV

SYNC

LT8607

INTV

CC

TR/SS

RT

GND

FB

PG

SW

BST

VIN5.7V to 42V

V

OUT

5V

750mA

POWER

GOOD

fSW = 2MHz

8607 TA01a

fSW = 2MHz

L = 4.7µH

I

OUT

(mA)0125

250

375

500

625

7505055

6065707580859095100

8607 TA01b

Step-Down Regulator with

2.5µA Quiescent Current

FEATURES DESCRIPTION

LT8607/LT8607B

Wide Input Voltage Range: 3.0V to 42V

®

Ultralow Quiescent Current Burst Mode

n

<3µA IQ Regulating 12VIN to 3.3V

n

Output Ripple <10mV

P-P

Operation:

OUT

High Efficiency 2MHz Synchronous Operation:

n

>93% Efficiency at 0.5A, 12VIN to 5V

OUT

750mA Maximum Continuous Output
Fast Minimum Switch-On Time: 35ns
Adjustable and Synchronizable: 200kHz to 2.2MHz
Spread Spectrum Frequency Modulation for Low EMI

Allows Use of Small Inductors
Low Dropout
Peak Current Mode Operation
Accurate 1V Enable Pin Threshold
Internal Compensation
Output Soft-Start and Tracking
Small Thermally Enhanced 10-Lead MSOP Package or

8-Lead 2mm × 2mm DFN Package

APPLICATIONS

General Purpose Step-Down Converter
Low EMI Step

Down

The LT®8607 is a compact, high efficiency, high speed syn-
chronous monolithic step-down switching regulator that
consumes only 1.7µA of non-switching quiescent current.
The LT8607 can deliver 750mA of continuous current.
Low ripple Burst Mode operation enables high efficiency
down to very low output currents while keeping the output
ripple below 10mV

. Internal compensation with peak

P-P

current mode topology allows the use of small inductors
and results in fast transient response and good loop sta­bility. The EN/UV pin has an accurate 1V threshold and
can be used to program VIN undervoltage lockout or to
shut down the LT8607 reducing the input supply current
to 1µA. The PG pin signals when V

is within ±8.5% of

OUT

the programmed output voltage as well as fault conditions.

The MSOP package includes a SYNC pin to synchronize
to an external clock, or to select Burst Mode operation
or pulse-skipping with or without spread spectrum; the
TR/SS pin programs soft-start or tracking. The DFN pack­age omits these pins and can be purchased in pulse-skip­ping or Burst Mode operation.

PACKAGE SYNC FUNCTIONALITY

LT8607MSE MSE Programmable
LT8607DFN DFN Burst Mode Operation
LT8607BDFN DFN Pulse-Skipping Mode

All registered trademarks and trademarks are the property of their respective owners.

TYPICAL APPLICATION

5V, 2MHz Step-Down

12VIN to 5V

For more information www.analog.comDocument Feedback

Efficiency

OUT

Rev. C

1

LT8607/LT8607B

TOP VIEW

EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB

ABSOLUTE MAXIMUM RATINGS

(Note 1)

VIN, EN/UV, PG ..........................................................42V

FB, TR/SS .
SYNC Voltage .

.................................................................4V

............................................................6V

PIN CONFIGURATION

Operating Junction Temperature Range (Note 2)

LT8607E ............................................ –40°C to 125°C

LT8607I ............................................. –40°C to 125°C

LT8607H ............................................ –40°C to 150°C

Storage Temperature Range

.................. –65°C to 150°C

TOP VIEW

10

1

BST

2

SW

INTV

CC

RT

SYNC

10-LEAD PLASTIC MSOP

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

3
4
5

MSE PACKAGE

θ

JA

11

GND

= 40°C/W

EN/UV

9

V

IN

PG

8

TR/SS

7

FB

6

1

BST

2

SW

3

INTV

CC

RT

4

8-LEAD (2mm × 2mm) PLASTIC DFN

DC PACKAGE

= 102°C/W

θ

JA

9

GND

8

7

6

5

EN/UV

V

IN

PG

FB

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LT8607EMSE#PBF LT8607EMSE#TRPBF LTGXJ 10-Lead Plastic MSOP –40°C to 125°C

LT8607IMSE#PBF LT8607IMSE#TRPBF LTGXJ 10-Lead Plastic MSOP –40°C to 125°C

LT8607HMSE#PBF LT8607HMSE#TRPBF LTGXJ 10-Lead Plastic MSOP –40°C to 150°C

LT8607EDC#PBF LT8607EDC#TRPBF LGXK 8-Lead Plastic (2mm × 2mm) Plastic DFN –40°C to 125°C

LT8607IDC#PBF LT8607IDC#TRPBF LGXK 8-Lead Plastic (2mm × 2mm) Plastic DFN –40°C to 125°C

LT8607HDC#PBF LT8607HDC#TRPBF LGXK 8-Lead Plastic (2mm × 2mm) Plastic DFN –40°C to 150°C

LT8607BEDC#PBF LT8607BEDC#TRPBF LGXM 8-Lead Plastic (2mm × 2mm) DFN –40°C to 125°C

LT8607BIDC#PBF LT8607BIDC#TRPBF LGXM 8-Lead Plastic (2mm × 2mm) DFN –40°C to 125°C

LT8607BHDC#PBF LT8607BHDC#TRPBF LGXM 8-Lead Plastic (2mm × 2mm) DFN –40°C to 150°C

Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.

Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.

ELECTRICAL CHARACTERISTICS

The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Input Voltage

Quiescent Current V

V

IN

Current in Regulation V

V

IN

2

= 0V

EN/UV

V

= 2V, Not Switching, V

EN/UV

= 6V, V

IN

V

IN

= 6V, V

OUT
OUT

= 0V or LT8607 DFN, VIN ≤ 36V

SYNC

= 2.7V, Output Load = 100µA
= 2.7V, Output Load = 1mA

For more information www.analog.com

l

l

l
l

2.5 3.0

3.2

1

1.7

56

500

12

90

700

V

5

µA
µA

µA
µA

Rev. C

LT8607/LT8607B

ELECTRICAL CHARACTERISTICS

The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Feedback Reference Voltage MSOP Package

VIN = 6V, I
V

IN

= 6V, I

LOAD
LOAD

DFN Package
V

= 6V, I

Feedback Voltage Line Regulation V

Feedback Pin Input Current V

Minimum On-Time I

Minimum Off Time I

IN

V

IN

IN

FB

LOAD

I

LOAD

LOAD

LOAD

= 6V, I

LOAD

= 4.0V to 40V

= 1V ±20 nA

= 750mA, SYNC = 0V or LT8607 DFN

= 750mA, SYNC = 1.9V or LT8607B DFN

= 300mA

Oscillator Frequency MSOP Package

= 221k, I

R

T

R

= 60.4k, I

T

R

= 18.2k, I

T

LOAD

LOAD
LOAD

DFN Package
R

= 221k, I

Top Power NMOS On-Resistance I

T

R

= 60.4k, I

T

R

= 18.2k, I

T

LOAD

LOAD

LOAD
LOAD

= 500mA 375 mΩ

Top Power NMOS Current Limit MSOP Package

DFN Package

= 100mA
= 100mA

= 100mA
= 100mA

= 350mA

= 350mA
= 350mA

= 350mA

= 350mA
= 350mA

0.774

l

0.762

0.771

l

0.753

l

l
l

l

l

155

l

640

l

1.90

l

140

l

610

l

1.85

l

1.2 1.6 2.0 A

l

1.2 1.7 2.2 A

Bottom Power NMOS On-Resistance 240 mΩ

SW Leakage Current V

EN/UV Pin Threshold EN/UV Rising

= 36V 5 µA

IN

l

0.99 1.05 1.11 V

EN/UV Pin Hysteresis 50 mV

EN/UV Pin Current V

PG Upper Threshold Offset from V

PG Lower Threshold Offset from V

FB

FB

= 2V ±20 nA

EN/UV

VFB Rising

VFB Falling

l

5.0 8.5 13.0 %

l

5.0 8.5 13.0 %

PG Hysteresis 0.5 %

PG Leakage V

PG Pull-Down Resistance V

Sync Low Input Voltage MSOP Only

Sync High Input Voltage INTV

TR/SS Source Current MSOP Only

= 42V ±200 nA

PG

= 0.1V 550 1200 Ω

PG

l

0.4 0.9 V

= 3.5V, MSOP Only

CC

l

l

1 2 3 µA

TR/SS Pull-Down Resistance Fault Condition, TR/SS = 0.1V, MSOP Only 300 900 Ω

Spread Spectrum Modulation Frequency V

Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime. Absolute Maximum Ratings are those values beyond
which the life of a device may be impaired.

Note 2: The LT8607E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization, and correlation with statistical process controls. The

= 3.3V, MSOP Only 0.5 3 6 kHz

SYNC

temperature range. The LT8607H is guaranteed over the full –40°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes. Operating lifetime is derated at junction
temperatures greater than 125°C.

Note 3: This IC includes overtemperature protection that is intended to
protect the device during overload conditions. Junction temperature will
exceed 150°C when overtemperature protection is active. Continuous
operation above the specified maximum operating junction temperature
will reduce lifetime.

LT8607I is guaranteed over the full –40°C to 125°C operating junction

0.778

0.778

0.778

0.778

0.782

0.798

0.785

0.803

±0.02 ±0.06 %/V

35
35

65
60

ns
ns

93 130 ns

200
700

2.00

200
700

2.00

245
760

2.10

260
790

2.15

kHz
kHz

MHz

kHz
kHz

MHz

2.7 3.2 V

Rev. C

V
V

V
V

For more information www.analog.com

3

LT8607/LT8607B

INPUT VOLTAGE (V)

210182634

42

–0.20

–0.15

–0.10

–0.05

0.00

0.05

0.10

0.15

0.20

CHANGE IN V

8607 G07

TEMPERATURE (°C)

–50

–103070

110

150

775

776

777

778

779

780

FB REGULATION VOLTAGE (mV)

8607 G05

OUTPUT CURRENT (mA)

0

125

250

375

500

625

750

–0.25

–0.20

–0.15

–0.10

–0.05

0.00

0.05

0.10

0.15

0.20

0.25

CHANGE IN V

(%)

8607 G06

fSW = 2MHz

VIN = 12V

VIN = 24V

L = 4.7µH

SYNC = 0V OR LT8607 DFN

I

OUT

(mA)

0

125

250

375

500

625

7505055

6065707580859095100

EFFICIENCY (%)

8607 G01

fSW = 2MHz

VIN = 12V

VIN = 24V

L = 4.7µH

I

OUT

(mA)

0.001

0.01

0.1110

100

900010

2030405060708090100

EFFICIENCY (%)

8607 G02

SYNC = 0V OR LT8607 DFN

fSW = 2MHz

VIN = 12V

VIN = 24V

L = 2.2µH

I

OUT

(mA)

0

125

250

375

500

625

7505055

6065707580859095100

EFFICIENCY (%)

8607 G03

SYNC = 0V OR LT8607 DFN

fSW = 2MHz

VIN = 12V

VIN = 24V

L = 2.2µH

I

OUT

(mA)

0.001

0.01

0.1110

100

900

0102030405060708090100

EFFICIENCY (%)

8607 G04

SYNC = 0V OR LT8607 DFN

L = 2.2µH

INPUT VOLTAGE (V)

210182634

42

2.00

2.25

2.50

2.75

3.00

3.25

3.50

3.75

4.00

4.25

4.50

I

8607 G08

SYNC = 0V OR LT8607 DFN

TEMPERATURE (°C)

–50

–103070

110

150

1.3

1.5

1.7

1.9

2.1

2.3

2.5

2.7

2.9

3.1

3.3

8607 G09

SYNC = 0V OR LT8607 DFN

TYPICAL PERFORMANCE CHARACTERISTICS

Efficiency (5V Output, Burst Mode
Operation)

Efficiency (5V Output, Burst Mode
Operation)

TA = 25°C, unless otherwise noted.

Efficiency (3.3V Output,
Burst Mode Operation)

Efficiency (3.3V Output,
Burst Mode Operation) FB Voltage Load Regulation

4

Line Regulation

No-Load Supply Current
(3.3V Output Switching)

For more information www.analog.com

No Load Supply Current vs
Temperature (Not Switching)

Rev. C

LT8607/LT8607B

DUTY CYCLE (%)

020406080

100

1.20

1.30

1.40

1.50

1.60

1.70

TOP FET CURRENT LIMIT (A)

8607 G10

SWITCH CURRENT (mA)

0

125

250

375

500

625

750050

100

150

200

250

300

SWITCH DROP (mV)

8607 G13

TOP SW
BOT SW

DUTY CYCLE = 0

TEMPERATURE (°C)

–50

–103070

110

150

1.50

1.55

1.60

1.65

1.70

TOP FET CURRENT LIMIT (A)

8607 G11

I

OUT

= 750mA

TEMPERATURE (°C)

–50

–30

–101030507090110

130

15032333435

363738

8607 G14

SWITCH CURRENT = 750mA

TOP SW
BOT SW

TEMPERATURE (°C)

–50

–30

–101030507090110

130

15050100

150

200

250

300

350

400

450

SWITCH DROP (mV)

8607 G12

I

OUT

= 350mA

TEMPERATURE (°C)

–50

–30

–101030507090110

130

15080859095

100

105

110

MINIMUM OFF-TIME (ns)

8607 G15

L: XFL4020-472ME

OUTPUT CURRENT (A)

0

125

250

375

500

625

750

0

50

100

150

200

250

300

350

DROPOUT VOLTAGE (mV)

8607 G16

RT = 18.2kΩ

TEMPERATURE (°C)

–50

–103070

110

150

1975

1980

1985

1990

1995

2000

2005

2010

2015

2020

2025

8607 G17

SYNC = 0V OR LT8607 DFN

OUTPUT CURRENT (mA)

0255075100

125

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

8607 G18

VIN = 12V

L = 2.2µH

V

OUT

= 3.3V

TYPICAL PERFORMANCE CHARACTERISTICS

Top FET Current Limit
vs Duty Cycle

Switch Drop vs Switch Current

Top FET Current Limit
vs Temperature Switch Drop vs Temperature

Minimum On-Time
vs Temperature

TA = 25°C, unless otherwise noted.

Minimum Off-Time
vs Temperature

Dropout Voltage vs Output Current

Switching Frequency
vs Temperature

For more information www.analog.com

Burst Frequency vs
Output Current

Rev. C

5

LT8607/LT8607B

INPUT VOLTAGE (V)

0510152025303540

45

0

25

5075100

125

150

OUTPUT CURRENT (mA)

8607 G19

VIN = 12V

L = 2.2µH

V

OUT

= 3.3V

RT = 18.2kΩ

SS VOLTAGE (V)

0

0.1

0.2

0.4

0.5

0.6

0.7

0.8

1.0

1.1

1.200.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

FB VOLTAGE (V)

8607 G21

TEMPERATURE (°C)

–50

–30

–101030507090110

130

150

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

8607 G22

V

IN

V

OUT

R

LOAD

= 50Ω

INPUT VOLTAGE (V)

0123456

7

0

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

8607 G24

TEMPERATURE (°C)

–50

–30

–101030507090110

130

150

2.00

2.25

2.50

2.75

3.00

3.25

8607 G23

V

IN

V

OUTRLOAD

= 6.66Ω

INPUT VOLTAGE (V)

0123456

7

0

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

8607 G25

FB VOLTAGE (V)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.00250

500

750

1000

1250

1500

1750

2000

2250

2500

8607 G20

TYPICAL PERFORMANCE CHARACTERISTICS

Minimum Load to Full
Frequency (SYNC Float to 1.9V)
(MSOP Package) or LT8607B DFN

Soft-Start Current vs Temperature
(MSOP Package)

Frequency Foldback

SYNC = 0V OR LT8607 DFN

V

TA = 25°C, unless otherwise noted.

Soft-Start Tracking
(MSOP Package)

UVLO vs Temperature

IN

6

Start-Up Dropout

Start-Up Dropout

Rev. C

For more information www.analog.com

LT8607/LT8607B

200mA/DIV

8607 G26

2MHz

8607 G29

SW

200mA/DIV

8607 G30

SW

200mA/DIV

8607 G27

2MHz

200mA/DIV

8607 G28

OUT

AMPLITUDE (dBµV/m)

50

1000

SW

TYPICAL PERFORMANCE CHARACTERISTICS

Switching Waveforms Switching Waveforms

I

LOAD

V

SW

5V/DIV

12VIN TO 5V

200mA/DIV

200ns/DIV

AT 500mA

OUT

Transient Response

I

LOAD

I

LOAD

V

SW

10V/DIV

36VIN TO 5V

OUT

200ns/DIV

AT 500mA

I

LOAD

TA = 25°C, unless otherwise noted.

Switching Waveforms
(Burst Mode)

V

OUT

20mV/DIV

I

LOAD

V

SW

10V/DIV

2µs/DIV

12VIN TO 5V
22µF C

OUT

AT 7.5mA

Transient Response

V

OUT

100mV/DIV

VIN =12V

= 5V

V

OUT

50mA TO 550mA

= 22µF

C

OUT

= 2MHz

f

45
40
35
30
25
20
15
10

5
0

–5

–10

V

OUT

100mV/DIV

200µs/DIV

VIN =12V

= 5V

V

OUT

250mA TO 750mA

= 22µF

C

OUT

= 2MHz

f

Radiated EMI Performance

(CISPR 25 Radiated Emission Test with Class 5 Peak Limits)

VERTICAL POLARIZATION
PEAK DETECTOR

CLASS 5 PEAK LIMIT
SPREAD SPECTRUM MODE
FIXED FREQUENCY

0 500 900300 700

DC2565A DEMO BOARD
WITH EMI FILTER INSTALLED
14V INPUT TO 5V OUTPUT AT 500mA, f

400 800200 600100

FREQUENCY (MHz)

= 2MHz

For more information www.analog.com

100µs/DIV

8607 G31

Rev. C

7

LT8607/LT8607B

PIN FUNCTIONS

BST: This pin is used to provide a drive voltage, higher
than the input voltage, to the topside power switch. Place
a 0.1µF boost capacitor as close as possible to the IC. Do
not place a resistor in series with this pin.

SW: The SW pin is the output of the internal power
switches. Connect this pin to the inductor and boost
capacitor. This node should be kept small on the PCB for
good performance.

INTV

: Internal 3.5V Regulator Bypass Pin. The internal

CC

power drivers and control circuits are powered from this
voltage. INTV

max output current is 20mA. Voltage on

CC

INTVCC will vary between 2.8V and 3.5V. Decouple this
pin to power ground with at least a 1µF low ESR ceramic
capacitor. Do not load the INTVCC pin with external circuitry.

RT: A resistor is tied between RT and ground to set the
switching frequency. When synchronizing, the RT resistor
should be chosen to set the LT8607 switching frequency
to equal or below the lowest synchronization input.

SYNC (MSOP Only): External Clock Synchronization
Input. Ground this pin for low ripple Burst Mode operation
at low output loads. Tie to a clock source for synchroni­zation to an external frequency. Leave floating for pulse­skipping mode with no spread spectrum modulation. Tie
to INTV

or tie to a voltage between 3.2V and 5.0V for

CC

pulse-skipping mode with spread spectrum modulation.
When in pulse-skipping mode, the I

regulating no load

Q

will increase to several mA. There is no SYNC pin on
the LT8607 DFN package. The LT8607 DFN internally
ties SYNC to ground. The LT8607B package internally
floatsSYNC.

FB: The LT8607 regulates the FB pin to 0.778V. Connect
the feedback resistor divider tap to this pin.

TR/SS (MSOP Only): Output Tracking and Soft-Start Pin.
This pin allows user control of output voltage ramp rate
during start-up. A TR/SS voltage below 0.778V forces the
LT8607 to regulate the FB pin to equal the TR/SS pin volt­age. When TR/SS is above 0.778V, the tracking function
is disabled and the internal reference resumes control of
the error amplifier. An internal 2µA pull-up current from
INTVCC on this pin allows a capacitor to program out­put voltage slew rate. This pin is pulled to ground with a
300Ω MOSFET during shutdown and fault conditions; use
a series resistor if driving from a low impedance output.
There is no TR/SS pin on the LT8607 or LT8607B DFN
and the node is internally floated.

PG: The PG pin is the open-drain output of an internal
comparator. PG remains low until the FB pin is within
±8.5% of the final regulation voltage, and there are no
fault conditions. PG is valid when VIN is above 3.2V and
when EN/UV is high. PG is pulled low when V

3.2V and EN/UV is low. If V

is near zero, PG will be high

IN

is above

IN

impedance.

: The VIN pin supplies current to the LT8607 internal

V

IN

circuitry and to the internal topside power switch. This pin
must be locally bypassed. Be sure to place the positive
terminal of the input capacitor as close as possible to the

pins, and the negative capacitor terminal as close as

V

IN

possible to the GND pins.

EN/UV: The LT8607 is shut down when this pin is low and
active when this pin is high. The hysteretic threshold volt­age is 1.05V going up and 1.00V going down. Tie to VIN
if the shutdown feature is not used. An external resistor
divider from V

can be used to program a VIN threshold

IN

below which the LT8607 will shut down.

GND: Exposed Pad Pin. The exposed pad must be con­nected to the negative terminal of the input capaci­tor and soldered to the PCB in order to lower the
thermalresistance.

8

Rev. C

For more information www.analog.com

BLOCK DIAGRAM

V

V

IN

R3
OPT

R4
OPT

V

OUT

C

FF

R2

C

SS

R

T

C

IN

EN/UV

PG

R

PG

R1

FB

TR/SS (MSOP ONLY)

RT

SYNC (MSOP ONLY)

IN

1V

INTERNAL 0.778V REF

+

SHDN

–

±8.5%

SHDN
TSD
INTVCC UVLO
VIN UVLO

2µA

ERROR

AMP

+
+
–

–
+

SLOPE COMP

OSCILLATOR

200kHz TO 2.2MHz

V

C

SHDN
TSD
V

UVLO

IN

BURST

DETECT

SWITCH

LOGIC

AND

ANTI-

SHOOT

THROUGH

3.5V
REG

LT8607/LT8607B

INTV

CC

C

8607 BD

VCC

C

BST

L

V

C

OUT

OUT

BST

M1

SW

M2

GND

OPERATION

The LT8607 is a monolithic constant frequency current
mode step-down DC/DC converter. An oscillator with
frequency set using a resistor on the RT pin turns on
the internal top power switch at the beginning of each
clock cycle. Current in the inductor then increases until
the top switch current comparator trips and turns off the
top power switch. The peak inductor current at which the
top switch turns off is controlled by the voltage on the
internal VC node. The error amplifier servos the VC node
by comparing the voltage on the VFB pin with an inter­nal 0.778V reference. When the load current increases it
causes a reduction in the feedback voltage relative to the
reference leading the error amplifier to raise the VC volt­age until the average inductor current matches the new
load current. When the top power switch turns off the
synchronous power switch turns on until the next clock
cycle begins or inductor current falls to zero. If overload
conditions result in excess current flowing through the
bottom switch, the next clock cycle will be delayed until
switch current returns to a safe level.

If the EN/UV pin is low, the LT8607 is shut down and
draws 1µA from the input. When the EN/UV pin is above

1.05V, the switching regulator becomes active.

To optimize efficiency at light loads, the LT8607 enters
Burst Mode operation during light load situations. Between
bursts, all circuitry associated with controlling the output

switch is shut down, reducing the input supply current to

1.7µA. In a typical application, 3.0µA will be consumed
from the input supply when regulating with no load. The
SYNC pin is tied low to use Burst Mode operation and can
be floated to use pulse-skipping mode. If a clock is applied
to the SYNC pin the part will synchronize to an external
clock frequency and operate in pulse-skipping mode. While
in pulse-skipping mode the oscillator operates continu­ously and positive SW transitions are aligned to the clock.
During light loads, switch pulses are skipped to regulate
the output and the quiescent current will be several mA.
The SYNC pin may be tied high for spread spectrum modu­lation mode, and the LT8607 will operate similar to pulse­skipping mode but vary the clock frequency to reduce EMI.
The LT8607 DFN has no SYNC pin and will always operate
in Burst Mode operation. The LT8607B has no SYNC pin
and will operate in pulse-skipping mode.

Comparators monitoring the FB pin voltage will pull the PG
pin low if the output voltage varies more than ±8.5% (typi

-

cal) from the set point, or if a fault condition is present.

The oscillator reduces the LT8607’s operating frequency
when the voltage at the FB pin is low and the part is in Burst
Mode operation. This frequency foldback helps to control
the inductor current when the output voltage is lower than
the programmed value which occurs duringstart-up.

Rev. C

For more information www.analog.com

9

LT8607/LT8607B

RT = 18.2kΩ

VIN = 12V

L = 2.2µH

V

OUT

= 3.3V

INPUT VOLTAGE (V)

0510152025303540

45025

5075100

125

150

8607 F02

200mA/DIV

8607 F03

OUTPUT CURRENT (mA)

0255075100

125

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

8607 F01

VIN = 12V

L = 2.2µH

V

OUT

= 3.3V

APPLICATIONS INFORMATION

Achieving Ultralow Quiescent Current

To enhance efficiency at light loads, the LT8607 enters
into low ripple Burst Mode operation, which keeps the
output capacitor charged to the desired output voltage
while minimizing the input quiescent current and mini­mizing output voltage ripple. In Burst Mode operation the
LT8607 delivers single small pulses of current to the out­put capacitor followed by sleep periods where the output
power is supplied by the output capacitor. While in sleep
mode the LT8607 consumes 1.7µA.

As the output load decreases, the frequency of single cur­rent pulses decreases (see Figure1) and the percentage
of time the LT8607 is in sleep mode increases, result­ing in much higher light load efficiency than for typical
converters. By maximizing the time between pulses, the
converter quiescent current approaches 3.0µA for a typi­cal application when there is no output load. Therefore,
to optimize the quiescent current performance at light
loads, the current in the feedback resistor divider must
be minimized as it appears to the output as load current.

programmed for Burst Mode operation and cannot enter
pulse-skipping mode. The LT8607B DFN is programmed
for pulse-skipping mode and cannot enter Burst Mode
operation.

SYNC = 0V OR LT8607 DFN

Figure1. Burst Frequency vs Output Current

While in Burst Mode operation the current limit of the
top switch is approximately 250mA resulting in output
voltage ripple shown in Figure3. Increasing the output
capacitance will decrease the output ripple proportionally.
As load ramps upward from zero the switching frequency
will increase but only up to the switching frequency
programmed by the resistor at the RT pin as shown in
Table1. The output load at which the LT8607 reaches the
programmed frequency varies based on input voltage,
output voltage, and inductor choice.

For some applications it is desirable for the LT8607 to
operate in pulse-skipping mode, offering two major differ­ences from Burst Mode operation. First is the clock stays
awake at all times and all switching cycles are aligned to
the clock. In this mode much of the internal circuitry is
awake at all times, increasing quiescent current to several
hundred µA. Second is that full switching frequency is
reached at lower output load than in Burst Mode operation
as shown in Figure2. To enable pulse-skipping mode the
SYNC pin is floated. To achieve spread spectrum modula­tion with pulse-skipping mode, the SYNC pin is tied high.
While a clock is applied to the SYNC pin the LT8607 will
also operate in pulse-skipping mode. The LT8607 DFN is

Figure2. Minimum Load to Full Frequency

(SYNC Float to 1.9V) (MSOP or LT8607B DFN)

V

OUT

20mV/DIV

I

LOAD

V

SW

10V/DIV

2µs/DIV

Figure3. Burst Mode Operation

Rev. C

10

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APPLICATIONS INFORMATION

V

V

V

( )

V

V

LT8607/LT8607B

FB Resistor Network

The output voltage is programmed with a resistor divider
between the output and the FB pin. Choose the resistor
values according to:

R1= R2

⎛
⎜

⎝

0.778V

OUT

–1

⎞
⎟

⎠

1% resistors are recommended to maintain output volt­age accuracy.

The total resistance of the FB resistor divider should be
selected to be as large as possible when good low load
efficiency is desired: The resistor divider generates a
small load on the output, which should be minimized to
optimize the quiescent current at low loads.

When using large FB resistors, a 10pF phase lead capaci­tor should be connected from V

OUT

to FB.

Setting the Switching Frequency

The LT8607 uses a constant frequency PWM architec­ture that can be programmed to switch from 200kHz
to 2.2MHz by using a resistor tied from the RT pin to
ground. A table showing the necessary RT value for a
desired switching frequency is in Table1. When in spread
spectrum modulation mode, the frequency is modulated
upwards of the frequency set by R

Table1. SW Frequency vs RT Value

fSW (MHz) RT (kΩ)

0.2 221

0.300 143

0.400 110

0.500 86.6

0.600 71.5

0.700 60.4

0.800 52.3

0.900 46.4

1.000 40.2

1.200 33.2

1.400 27.4

1.600 23.7

1.800 20.5

2.000 18.2

2.200 16.2

.

T

Operating Frequency Selection and Trade-Offs

Selection of the operating frequency is a trade-off between
efficiency, component size, and input voltage range. The
advantage of high frequency operation is that smaller
inductor and capacitor values may be used. The disadvan­tages are lower efficiency and a smaller input voltagerange.

The highest switching frequency (f

SW(MAX)

) for a given

application can be calculated as follows:

+

OUT

VIN– V

f

SW(MAX)

=

t

ON(MIN)

where VIN is the typical input voltage, V
voltage, V

SW(TOP)

and V

SW(BOT)

SW(BOT)

SW( TOP)

+ V

SW(BOT)

is the output

OUT

are the internal switch
drops (~0.25V, ~0.125V, respectively at max load) and
t

ON(MIN)

is the minimum top switch on-time (see Electrical
Characteristics). This equation shows that slower switch­ing frequency is necessary to accommodate a high VIN/

ratio.

V

OUT

For transient operation VIN may go as high as the Abs Max
rating regardless of the RT value, however the LT8607
will reduce switching frequency as necessary to maintain
control of inductor current to assure safe operation.

The LT8607 is capable of maximum duty cycle approach­ing 100%, and the VIN to V
R

of the top switch. In this mode the LT8607 skips

DS(ON)

dropout is limited by the

OUT

switch cycles, resulting in a lower switching frequency
than programmed by RT.

For applications that cannot allow deviation from the pro­grammed switching frequency at low VIN/V

ratios use

OUT

the following formula to set switching frequency:

+

V

IN(MIN)

where V

OUT

=

1– fSW• t

is the minimum input voltage without

IN(MIN)

skipped cycles, V
V

SW(BOT)

are the internal switch drops (~0.25V, ~0.125V,
respectively at max load), f
(set by RT), and t

SW(BOT)

OFF(MIN)

is the output voltage, V

OUT

OFF(MIN)

– V

SW(BOT)

is the switching frequency

SW

is the minimum switch off-

+ V

SW( TOP)

SW(TOP)

and

time. Note that higher switching frequency will increase
the minimum input voltage below which cycles will be
dropped to achieve higher duty cycle.

Rev. C

For more information www.analog.com

11

LT8607/LT8607B

V

V

SW

1

2

ΔI

2

APPLICATIONS INFORMATION

Inductor Selection and Maximum Output Current

The LT8607 is designed to minimize solution size by
allowing the inductor to be chosen based on the output
load requirements of the application. During overload or
short circuit conditions the LT8607 safely tolerates opera

­tion with a saturated inductor through the use of a high
speed peak-current mode architecture.

A good first choice for the inductor value is:

+

OUT

L =

where fSW is the switching frequency in MHz, V
the output voltage, V

SW(BOT)

f

• 2

SW(BOT)

is

OUT

is the bottom switch drop

(~0.125V) and L is the inductor value in µH.

To avoid overheating and poor efficiency, an inductor
must be chosen with an RMS current rating that is greater
than the maximum expected output load of the applica­tion. In addition, the saturation current (typically labeled

) rating of the inductor must be higher than the load

I

SAT

current plus 1/2 of in inductor ripple current:

I

L(PEAK)

= I

LOAD(MAX)

+

Δ

L

where ∆IL is the inductor ripple current as calculated sev­eral paragraphs below and I

LOAD(MAX)

is the maximum

output load for a given application.

As a quick example, an application requiring 0.25A output
should use an inductor with an RMS rating of greater
than 0.5A and an I

of greater than 0.7A. To keep the

SAT

efficiency high, the series resistance (DCR) should be less
than 0.04Ω, and the core material should be intended for
high frequency applications.

The LT8607 limits the peak switch current in order to
protect the switches and the system from overload faults.
The top switch current limit (I

) is at least 1.2A at low

LIM

duty cycles and decreases linearly to at least 0.9A at D =

0.8. The inductor value must then be sufficient to supply
the desired maximum output current (I

OUT(MAX)

is a function of the switch current limit (I

), which

) and the

LIM

ripple current:

I

OUT(MAX)

= I

LIM

L

–

The peak-to-peak ripple current in the inductor can be
calculated as follows:

⎛

V

ΔI

OUT

=

L

L • f

SW

V

1–

⎜

V

⎝

IN(MAX)

OUT

⎞
⎟

⎠

where fSW is the switching frequency of the LT8607, and
L is the value of the inductor. Therefore, the maximum
output current that the LT8607 will deliver depends on
the switch current limit, the inductor value, and the input
and output voltages. The inductor value may have to be
increased if the inductor ripple current does not allow
sufficient maximum output current (I

OUT(MAX)

) given the
switching frequency, and maximum input voltage used in
the desired application.

The optimum inductor for a given application may differ
from the one indicated by this design guide. A larger value
inductor provides a higher maximum load current and
reduces the output voltage ripple. For applications requir­ing smaller load currents, the value of the inductor may
be lower and the LT8607 may operate with higher ripple
current. This allows use of a physically smaller inductor,
or one with a lower DCR resulting in higher efficiency. Be
aware that low inductance may result in discontinuous
mode operation, which further reduces maximum load
current.

For more information about maximum output current and
discontinuous operation, see Analog Devices Application
Note 44.

Finally, for duty cycles greater than 50% (V

OUT/VIN

> 0.5),
a minimum inductance is required to avoid sub-harmonic
oscillation. See Application Note 19.

Input Capacitor

Bypass the input of the LT8607 circuit with a ceramic
capacitor of X7R or X5R type. Y5V types have poor per­formance over temperature and applied voltage, and
should not be used. A 4.7µF to 10µF ceramic capacitor
is adequate to bypass the LT8607 and will easily handle
the ripple current. Note that larger input capacitance is
required when a lower switching frequency is used. If
the input power source has high impedance, or there is

Rev. C

12

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APPLICATIONS INFORMATION

100

OUT

SW

LT8607/LT8607B

significant inductance due to long wires or cables, addi­tional bulk capacitance may be necessary. This can be
provided with a low performance electrolytic capacitor.

Step-down regulators draw current from the input sup­ply in pulses with very fast rise and fall times. The input
capacitor is required to reduce the resulting voltage rip­ple at the LT8607 and to force this very high frequency
switching current into a tight local loop, minimizing EMI.
A 4.7µF capacitor is capable of this task, but only if it is
placed close to the LT8607 (see the PCB Layout section).
A second precaution regarding the ceramic input capaci­tor concerns the maximum input voltage rating of the
LT8607. A ceramic input capacitor combined with trace
or cable inductance forms a high quality (under damped)
tank circuit. If the LT8607 circuit is plugged into a live
supply, the input voltage can ring to twice its nominal
value, possibly exceeding the LT8607’s voltage rating.
This situation is easily avoided (see Analog Devices
Application Note 88).

Output Capacitor and Output Ripple

The output capacitor has two essential functions. Along
with the inductor, it filters the square wave generated
by the LT8607 to produce the DC output. In this role it
determines the output ripple, thus low impedance at the
switching frequency is important. The second function is
to store energy in order to satisfy transient loads and sta­bilize the LT8607’s control loop. Ceramic capacitors have
very low equivalent series resistance (ESR) and provide
the best ripple performance. A good starting value is:

cause loop instability. See the Typical Applications in this
data sheet for suggested capacitor values.

When choosing a capacitor, special attention should be
given to the data sheet to calculate the effective capaci­tance under the relevant operating conditions of voltage
bias and temperature. A physically larger capacitor or one
with a higher voltage rating may be required.

Ceramic Capacitors

Ceramic capacitors are small, robust and have very low
ESR. However, ceramic capacitors can cause problems
when used with the LT8607 due to their piezoelectric
nature. When in Burst Mode operation, the LT8607’s
switching frequency depends on the load current, and at
very light loads the LT8607 can excite the ceramic capacitor
at audio frequencies, generating audible noise. Since the
LT8607 operates at a lower current limit during Burst Mode
operation, the noise is typically very quiet to a casual ear.
If this is unacceptable, use a high performance tantalum
or electrolytic capacitor at the output.

A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LT8607. As pre­viously mentioned, a ceramic input capacitor combined
with trace or cable inductance forms a high quality (under
damped) tank circuit. If the LT8607 circuit is plugged into
a live supply, the input voltage can ring to twice its nomi­nal value, possibly exceeding the LT8607’s rating. This
situation is easily avoided (see Analog Devices Application
Note 88).

C

=

OUT

V

where fSW is in MHz, and C

• f

is the recommended output

OUT

capacitance in µF. Use X5R or X7R types. This choice will
provide low output ripple and good transient response.
Transient performance can be improved with a higher value
output capacitor and the addition of a feedforward capaci­tor placed between V

and FB. Increasing the output

OUT

capacitance will also decrease the output voltage ripple. A
lower value of output capacitor can be used to save space
and cost but transient performance will suffer and may

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Enable Pin

The LT8607 is in shutdown when the EN pin is low and
active when the pin is high. The rising threshold of the EN
comparator is 1.05V, with 50mV of hysteresis. The EN pin
can be tied to VIN if the shutdown feature is not used, or
tied to a logic level if shutdown control is required.

Adding a resistor divider from VIN to EN programs the
LT8607 to regulate the output only when VIN is above
a desired voltage (see Block Diagram). Typically, this
threshold, V

, is used in situations where the input

IN(EN)

Rev. C

13

LT8607/LT8607B

R3

APPLICATIONS INFORMATION

supply is current limited, or has a relatively high source
resistance. A switching regulator draws constant power
from the source, so source current increases as source
voltage drops. This looks like a negative resistance load
to the source and can cause the source to current limit or
latch low under low source voltage conditions. The V

IN(EN)

threshold prevents the regulator from operating at source
voltages where the problems might occur. This threshold
can be adjusted by setting the values R3 and R4 such that
they satisfy the following equation:

V

IN(EN)

⎛

=

⎜

⎝

where the LT8607 will remain off until VIN is above V

R4

+ 1

⎞
⎟

⎠

•1V

IN(EN)

.
Due to the comparator’s hysteresis, switching will not
stop until the input falls slightly below V

IN(EN)

.

When in Burst Mode operation for light-load currents,
the current through the V

resistor network can eas-

IN(EN)

ily be greater than the supply current consumed by the
LT8607. Therefore, the V

resistors should be large

IN(EN)

to minimize their effect on efficiency at low loads.

INTV

Regulator

CC

can be externally driven by another voltage source. From
0V to 0.778V, the TR/SS voltage will override the internal

0.778V reference input to the error amplifier, thus regulat

­ing the FB pin voltage to that of TR/SS pin. When TR/SS
is above 0.778V, tracking is disabled and the feedback
voltage will regulate to the internal reference voltage.

An active pull-down circuit is connected to the TR/SS pin
which will discharge the external soft-start capacitor in
the case of fault conditions and restart the ramp when the
faults are cleared. Fault conditions that clear the soft-start
capacitor are the EN/UV pin transitioning low, VIN volt­age falling too low, or thermal shutdown. The LT8607 and
LT8607B DFN does not have the TR/SS pin or functionality.

Output Power Good

When the LT8607’s output voltage is within the ±8.5%
window of the regulation point, which is a VFB voltage in
the range of 0.716V to 0.849V (typical), the output voltage
is considered good and the open-drain PG pin goes high
impedance and is typically pulled high with an external
resistor. Otherwise, the internal drain pull-down device
will pull the PG pin low. To prevent glitching both the
upper and lower thresholds include 0.5% of hysteresis.

An internal low dropout (LDO) regulator produces the

3.5V supply from VIN that powers the drivers and the
internal bias circuitry. The INTVCC can supply enough cur­rent for the LT8607’s circuitry and must be bypassed to
ground with a minimum of 1µF ceramic capacitor. Good
bypassing is necessary to supply the high transient
currents required by the power MOSFET gate drivers.
Applications with high input voltage and high switching
frequency will increase die temperature because of the
higher power dissipation across the LDO. Do not connect
an external load to the INTVCC pin.

Output Voltage Tracking and Soft-Start (MSOP Only)

The LT8607 allows the user to program its output voltage
ramp rate by means of the TR/SS pin. An internal 2µA
pulls up the TR/SS pin to INTVCC. Putting an external
capacitor on TR/SS enables soft-starting the output to
prevent current surge on the input supply. During the soft­start ramp the output voltage will proportionally track the
TR/SS pin voltage. For output tracking applications, TR/SS

The PG pin is also actively pulled low during several fault
conditions: EN/UV pin is below 1V, INTV
low, V

is too low, or thermal shutdown.

IN

has fallen too

CC

Synchronization (MSOP Only)

To select low ripple Burst Mode operation, tie the SYNC
pin below 0.4V (this can be ground or a logic low out­put). To synchronize the LT8607 oscillator to an external
frequency connect a square wave (with 20% to 80% duty
cycle) to the SYNC pin. The square wave amplitude should
have valleys that are below 0.9V and peaks above 2.7V
(up to 5V).

The LT8607 will not enter Burst Mode operation at low
output loads while synchronized to an external clock, but
instead will pulse skip to maintain regulation. The LT8607
may be synchronized over a 200kHz to 2.2MHz range. The
RT resistor should be chosen to set the LT8607 switch­ing frequency equal to or below the lowest synchroni­zation input. For example, if the synchronization signal
will be 500kHz and higher, the RT should be selected for

Rev. C

14

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APPLICATIONS INFORMATION

LT8607/LT8607B

500kHz. The slope compensation is set by the RT value,
while the minimum slope compensation required to avoid
subharmonic oscillations is established by the inductor
size, input voltage, and output voltage. Since the syn­chronization frequency will not change the slopes of the
inductor current waveform, if the inductor is large enough
to avoid subharmonic oscillations at the frequency set by

, then the slope compensation will be sufficient for all

R

T

synchronization frequencies.

For some applications it is desirable for the LT8607 to
operate in pulse-skipping mode, offering two major differ­ences from Burst Mode operation. First is the clock stays
awake at all times and all switching cycles are aligned
to the clock. Second is that full switching frequency is
reached at lower output load than in Burst Mode opera­tion as shown in Figure2 in an earlier section. These two
differences come at the expense of increased quiescent
current. To enable pulse-skipping mode the SYNC pin is
floated.

For some applications, reduced EMI operation may be
desirable, which can be achieved through spread spec­trum modulation. This mode operates similar to pulse
skipping mode operation, with the key difference that the
switching frequency is modulated up and down by a 3kHz
triangle wave. The modulation has the frequency set by RT
as the low frequency, and modulates up to approximately
20% higher than the frequency set by RT. To enable spread
spectrum mode, tie SYNC to INTVCC or drive to a voltage
between 3.2V and 5V.

The LT8607 does not operate in forced continuous mode
regardless of SYNC signal. The LT8607 DFN is always
programmed for Burst Mode operation and cannot enter
pulse-skipping mode. The LT8607B DFN is programmed
for pulse-skipping mode and cannot enter Burst Mode
operation.

Shorted and Reversed Input Protection

bottom switch current is monitored such that if inductor
current is beyond safe levels switching of the top switch
will be delayed until such time as the inductor current
falls to safe levels. This allows for tailoring the LT8607
to individual applications and limiting thermal dissipation
during short circuit conditions.

Frequency foldback behavior depends on the state of the
SYNC pin: If the SYNC pin is low the switching frequency
will slow while the output voltage is lower than the pro­grammed level. If the SYNC pin is connected to a clock
source, tied high or floated, the LT8607 will stay at the
programmed frequency without foldback and only slow
switching if the inductor current exceeds safe levels.

There is another situation to consider in systems where
the output will be held high when the input to the LT8607
is absent. This may occur in battery charging applications
or in battery backup systems where a battery or some
other supply is diode ORed with the LT8607’s output.
If the VIN pin is allowed to float and the EN pin is held
high (either by a logic signal or because it is tied to VIN),
then the LT8607’s internal circuitry will pull its quiescent
current through its SW pin. This is acceptable if the sys­tem can tolerate several µA in this state. If the EN pin is
grounded the SW pin current will drop to near 0.7µA.
However, if the VIN pin is grounded while the output is
held high, regardless of EN, parasitic body diodes inside
the LT8607 can pull current from the output through the
SW pin and the V
the V

and EN/UV pins that will allow the LT8607 to run

IN

pin. Figure4 shows a connection of

IN

only when the input voltage is present and that protects
against a shorted or reversed input.

D1

V

IN

V

IN

LT8607

EN/UV

GND

8607 F04

The LT8607 will tolerate a shorted output. Several features
are used for protection during output short-circuit and
brownout conditions. The first is the switching frequency
will be folded back while the output is lower than the set
point to maintain inductor current control. Second, the

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Figure4. Reverse VIN Protection

Rev. C

15

LT8607/LT8607B

8607 F05

OUT

APPLICATIONS INFORMATION

PCB Layout

For proper operation and minimum EMI, care must be
taken during printed circuit board layout. Note that large,
switched currents flow in the LT8607’s VIN pins, GND
pins, and the input capacitor (C

). The loop formed by

IN

the input capacitor should be as small as possible by
placing the capacitor adjacent to the VIN and GND pins.
When using a physically large input capacitor the result­ing loop may become too large in which case using a
small case/value capacitor placed close to the V

IN

and
GND pins plus a larger capacitor further away is pre­ferred. These components, along with the inductor and
output capacitor, should be placed on the same side of
the circuit board, and their connections should be made
on that layer. Place a local, unbroken ground plane under
the application circuit on the layer closest to the surface
layer. The SW and BOOST nodes should be as small as
possible. Finally, keep the FB and RT nodes small so
that the ground traces will shield them from the SW and
BOOST nodes. The exposed pad on the bottom of the
package must be soldered to ground so that the pad is
connected to ground electrically and also acts as a heat
sink thermally. To keep thermal resistance low, extend

the ground plane as much as possible, and add thermal
vias under and near the LT8607 to additional ground
planes within the circuit board and on the bottom side.

Thermal Considerations

For higher ambient temperatures, care should be taken in
the layout of the PCB to ensure good heat sinking of the
LT8607. Figure5 shows the recommended component
placement with trace, ground plane and via locations.
The exposed pad on the bottom of the package must be
soldered to a ground plane. This ground should be tied
to large copper layers below with thermal vias; these lay­ers will spread heat dissipated by the LT8607. Placing
additional vias can reduce thermal resistance further. The
maximum load current should be derated as the ambient
temperature approaches the maximum junction rating.
Power dissipation within the LT8607 can be estimated
by calculating the total power loss from an efficiency
measurement and subtracting the inductor loss. The
die temperature is calculated by multiplying the LT8607
power dissipation by the thermal resistance from junction
to ambient. The LT8607 will stop switching and indicate
a fault condition if safe junction temperature is exceeded.

16

C

OUT

GND VIA VIN VIA V

For more information www.analog.com

GROUND PLANE ON LAYER 2

L

C

BST

1

CIN(OPT)

R1

C

FF

C

VCC

R

T

VIA EN/UV VIA OTHER SIGNAL VIA

Figure5. PCB Layout

C

IN

R

PG

R3

R2

C

SS

R4

Rev. C

TYPICAL APPLICATIONS

C1

0.1µF

C2

4.7µF
X7R
1206

C3
1µF

C4
22µF
X7R
1206

8607 TA02

C5

10pF

L1

4.7µH

R1

18.2k

R2
1M

R3
187k

L1: XFL4020-472ME

R4
100k

C6

10nF

V

IN

EN/UV

SYNC

LT8607

INTV

CC

TR/SS

RT

GND

FB

PG

SW

BST

VIN5.6V to 42V

V

OUT

5V

750mA

POWER

GOOD

fSW = 2MHz

C1

0.1µF

C2

4.7µF
X7R
1206

C3
1µF

C4
22µF
X7R
1206

8607 TA03

C5

10pF

L1

2.2µH

R1

18.2k

R2
1M

R3
309k

L1: XFL3012-222ME

R4
100k

C6

10nF

V

IN

EN/UV

SYNC

LT8607

INTV

CC

TR/SS

RT

GND

FB

PG

SW

BST

VIN3.9V to 42V

V

OUT

3.3V

750mA

POWER

GOOD

fSW = 2MHz

C1

0.1µF

C2

4.7µF
X7R
1206

C3
1µF

C4
22µF
X7R
1206

8607 TA04

C5

10pF

L1

22µH

R1

40.2k

R2
1M

R3

69.8k

L1: MSS6132-223ML

R4
100k

C6

10nF

V

IN

EN/UV

SYNC

LT8607

INTV

CC

TR/SS

RT

GND

FB

PG

SW

BST

VIN12.7V to 42V

V

OUT

12V

750mA

POWER

GOOD

fSW = 1MHz

LT8607/LT8607B

5V, 2MHz Step-Down

3.3V, 2MHz Step-Down

12V, 1MHz Step-Down

For more information www.analog.com

Rev. C

17

LT8607/LT8607B

C1

0.1µF

C2

4.7µF

C3
1µF

C4
22µF
X7R
1206

8607 TA05

C5

10pF

L1

2.2µH

R1

18.2k

R2
1M

R3
768k

L1: XFL3012-222ME

R4
100k

C6

10nF

V

IN

EN/UV

SYNC

LT8607

INTV

CC

TR/SS

RT

GND

FB

PG

SW

BST

V

IN

3.2V to 20V

(42V TRANSIENT)

V

OUT

1.8V

750mA

POWER

GOOD

fSW = 2MHz

C1

0.1µF

C2

4.7µFC933µFC74.7µFC84.7µF

C3
1µF

C4
22µF
X7R
1206

8607 TA06

C5

10pF

L1

22µHL34.7µHL2BEAD

R1
110k

R2
1M

R3
187k

C2, C7, C8: X7R 1206
C9: 63SXV33M
L1: MSS6132-223
L2: BKP2125HS101-T

R4
100k

C6

10nF

V

IN

EN/UV

SYNC

LT8607

(MSOP)

INTV

CC

TR/SS

RT

GND

FB

PG

SW

BST

V

OUT

5V

750mA

POWER

GOOD

fSW = 400kHz

VIN5.8V to 40V

+

TYPICAL APPLICATIONS

1.8V, 2MHz Step-Down

Ultralow EMI, 5V, 1.5A Step-Down

18

Rev. C

For more information www.analog.com

PACKAGE DESCRIPTION

GAUGE PLANE

(.0120

NO MEASUREMENT PURPOSE

MSE Package

1.88 ±0.102

(.074 ±.004)

10-Lead Plastic MSOP, Exposed Die Pad

(Reference LTC DWG # 05-08-1664 Rev I)

BOTTOM VIEW OF

EXPOSED PAD OPTION

0.889 ±0.127
(.035 ±.005)

1

1.88

(.074)

LT8607/LT8607B

0.29

1.68

(.066)

REF

5.10

(.201)

MIN

0.305 ± 0.038
±.0015)

TYP

RECOMMENDED SOLDER PAD LAYOUT

0.18

(.007)

NOTE:

1. DIMENSIONS IN MILLIMETER/(INCH)

2. DRAWING NOT TO SCALE

3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX

6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD
SHALL NOT EXCEED 0.254mm (.010") PER SIDE.

0.254

(.010)

1.68 ±0.102

(.066 ±.004)

0.50

(.0197)

BSC

DETAIL “A”

DETAIL “A”

0° – 6° TYP

0.53 ±0.152

(.021 ±.006)

3.20 – 3.45

(.126 – .136)

SEATING

PLANE

10

3.00 ±0.102
(.118 ±.004)

(NOTE 3)

4.90 ±0.152

(.193 ±.006)

1 2

1.10

(.043)

MAX

0.17 –0.27

(.007 – .011)

TYP

0.50

(.0197)

BSC

8910

7

6

4 5

3

DETAIL “B”

0.497 ±0.076
(.0196 ±.003)

3.00 ±0.102

(.118 ±.004)

(NOTE 4)

0.86

(.034)

REF

0.1016 ±0.0508
(.004 ±.002)

MSOP (MSE) 0213 REV I

0.05 REF

DETAIL “B”

CORNER TAIL IS PART OF

THE LEADFRAME FEATURE.

FOR REFERENCE ONLY

REF

For more information www.analog.com

Rev. C

19

LT8607/LT8607B

2.60

PIN 1 NOTCH

DC8 Package

PACKAGE DESCRIPTION

0.23

0.90
REF

REF

±0.05

0.335 REF

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

PIN 1 BAR

TOP MARK

(SEE NOTE 6)

0.200 REF

8-Lead Plastic DFN (2mm × 2mm)

(Reference LTC DWG # 05-08-1939 Rev Ø)

Exposed Pad Variation AA

1.8 REF

0.85 ±0.05

PACKAGE
OUTLINE

0.25 ±0.05

0.45 BSC

0.23
REF

0.335

2.00 ±0.05
(4 SIDES)

0.75 ±0.05

REF

BOTTOM VIEW—EXPOSED PAD

2.00 SQ ±0.05

1.8 REF

4

85

(DC8MA) DFN 0113 REV Ø

1

0.45 BSC

0.55 ±0.05

R = 0.15

0.23 ±0.05

0.00 – 0.05

NOTE:

1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE

20

Rev. C

For more information www.analog.com

LT8607/LT8607B

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER

A 06/17 Added DFN package option.

Clarified electrical parameters for DFN package option.
Clarified graphs for MSOP package option.
Clarified Pins Functions for DFN package option.
Clarified Operation to include DFN option.
Clarified Applications last paragraph and Figure2 to include DFN option.
Clarified Applications section to include DFN operation.
Added DFN Package Description.

B 11/17 Added H-grade option

Clarified Oscillator Frequency R
Clarified efficiency graph
Clarified Block Diagram
Added Figure5
Clarified Typical Applications for MSOP package option

C 11/18 Added B version

Added table to clarify versions
Modified text in Description to add DFN functionality
Added B version to Order Information
Clarified Minimum On-Time Conditions
Clarified efficiency graphs
Clarified Burst Frequency vs Output Current graph
Clarified Minimum Load to Full Frequency and Frequency Foldback graphs
Clarified Pin Functions on SYNC and TR/SS
Clarified Operation third paragraph
Clarified last paragraph to include DFN B version and Figures 1, 3
Clarified Applications to include DFN B version
Clarified PCB Layout

conditions

T

1, 2
2, 3

6
8
9

10

14, 15

20

2, 3

3
4
9

16

18, 22

All

1
1
2
3
4
5
6
8

9
10
15
16

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

For more information www.analog.com

Rev. C

21

LT8607/LT8607B

C7

0.1µF

C8

4.7µF

C10
22µF

8607 TA07

C11

10pF

L2

2.2µH

R5

18.2k

R10
22k

R6
1M

R7
309k

L2: XFL3012-222ME
C2, C4, C8, C10: X7R 1206

R8
100k

C12

1µF

V

IN

EN/UV

SYNC

LT8607

(MSOP)

INTVCCTR/SS

RT

GND

FB

PGSWBST

V

OUT

3.3V

750mA

POWER

GOOD

fSW = 2MHz

C1

0.1µF

C2

4.7µF

C3
1µF

C4
22µF

C5

10pF

L1

4.7µHR118.2k

R2
1M

R3
187k

L1: XFL4020-472ME

R4
100k

C6

10nF

V

IN

EN/UV

SYNC

LT8607

(MSOP)

INTV

CC

TR/SSRTGND

FB

PG

SW

BST

VIN5.7V to 42V

V

OUT

5.0V

750mA

POWER

GOOD

fSW = 2MHz

R9

80.6k

TYPICAL APPLICATION

5V and 3.3V with Ratio Tracking

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22

Step-Down DC/DC Converter with I

Step-Down DC/DC Converter with I

= 3µA

Q

= 2.5µA

Q

42V, 2A/3A Peak, 93% Efficiency, 2.2MHz Synchronous MicroPower Step­Down DC/DC Converter with I

Step-Down DC/DC Converter with I

= 2.5µA

Q

= 2.5µA

Q

®

2

42V, 3.5A, 96% Efficiency, 2.2MHz Synchronous MicroPower
Step-Down DC/DC Converter with IQ = 2.5µA

Step-Down DC/DC Converter with I

Step-Down DC/DC Converter with I

DC/DC Converter with I

DC/DC Converter with I

DC Converter with I

= 2.5µA

Q

= 2.5µA

Q

= 2.5µA

Q

Step-Down DC/DC Converter with I

Step-Down DC/DC Converter with I

Synchronous MicroPower Step-Down DC/DC Converter with I

= 5µA

Q

= 2.5µA

Q

= 2.5µA

Q

= 2.5µA

Q

= 25µA

Q

For more information www.analog.com

: 3V to 42V, V

V

IN

= 0.778V, IQ = 3µA, ISD = <1µA,

OUT

MSOP-10E Package

: 3V to 42V, V

V

IN

= 0.778V, IQ = 2.5µA, ISD = <1µA,

OUT

MSOP-10E Package

: 3V to 42V, V

V

IN

= 0.782V, IQ = 2.5µA, ISD = <1µA,

OUT

MSOP-10E Package

: 3V to 42V, V

V

IN

= 0.774V, IQ = 2.5µA, ISD = <1µA,

OUT

3mm × 3mm LQFN-16 Package

: 3.4V to 42V, V

V

IN

= 0.97V, IQ = 2.5µA, ISD = <1µA,

OUT

MSOP-16E Package

: 3.4V to 42V, V

V

IN

= 0.8V, IQ = 5µA, ISD = <1µA,

OUT

TSSOP-28E, 3mm × 6mm QFN-28 Packages

: 3.4V to 65V, V

V

IN

= 0.97V, IQ = 2.5µA, ISD = <1µA,

OUT

MSOP-16E 3mm × 5mm QFN-24 Packages

: 3.4V to 42V, V

V

IN

= 0.97V, IQ = 2.5µA, ISD = <1µA,

OUT

3mm × 4mm QFN-18 Package

: 3.4V to 42V, V

V

IN

= 0.97V, IQ = 3µA, ISD = <1µA,

OUT

3mm × 6mm QFN-28 Package

: 3.4V to 42V, V

V

IN

= 0.97V, IQ = 2.5µA, ISD = <1µA,

OUT

3mm × 4mm QFN-18 Package

: 3.4V to 42V, V

V

IN

= 0.97V, IQ = 2.5µA, ISD = <1µA,

OUT

4mm × 4mm LQFN-24 Package

: 3.4V to 65V, V

V

IN

= 0.97V, IQ = 2.5µA, ISD = <1µA,

OUT

4mm × 6mm LQFN-32 Package

: 3V to 42V, V

V

IN

= 0.8V, IQ = 25µA, ISD = <1µA,

OUT

6mm × 6mm QFN-40 Package

www.analog.com

 ANALOG DEVICES, INC. 2018

Rev. C

11/18