LINEAR TECHNOLOGY LTC3719 Technical data

FEATURES

LTC3719

2-Phase, High Efficiency,

Step-Down Controller for

AMD Opteron™ CPUs

U

DESCRIPTIO

■

Output Stages Operate Antiphase Reducing Input
and Output Capacitance Requirements and Power
Supply Induced Noise

■

Dual Input Supply Capability for Load Sharing

■

5-Bit AMD CPU VID Code:

V

= 0.8V to 1.55V

■

■

■

■

■

■

■

■

■

■

■

■

■

OUT

±1% Output Voltage Accuracy
True Remote Sensing Differential Amplifier
Power Good Output Voltage Monitor
Supports Active Voltage Positioning

Current Mode Control Ensures Current Sharing
OPTI-LOOP® Compensation Minimizes C

OUT

Three Operational Modes: PWM, Burst and Cycle Skip
Programmable Fixed Frequency: 150kHz to 300kHz
Wide VIN Range: 4V to 36V Operation
Adjustable Soft-Start Current Ramping
Internal Current Foldback and Short-Circuit Shutdown
Overvoltage Soft Latch Eliminates Nuisance Trips
Available in 36-Lead Narrow (0.209) SSOP Package

U

APPLICATIO S

■

Servers and Workstations

, LTC and LT are registered trademarks of Linear Technology Corporation.

OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology Corporation.
AMD Opteron is a trademark of Advanced Micro Devices, Inc.

The LTC®3719 is a 2-phase, VID programmable, synchro­nous step-down switching regulator controller that drives
two N-channel external power MOSFET stages in a fixed fre­quency architecture. The 2-phase controller drives its two
output stages out of phase at frequencies up to 300kHz to
minimize the RMS ripple currents in both input and output
capacitors. The 2-phase technique effectively multiplies the
fundamental frequency by two, improving transient re­sponse while operating each channel at an optimum fre­quency for efficiency. Thermal design is also simplified.

An operating mode select pin (FCB) can be used to select
among three modes including Burst Mode® operation for
highest efficiency. An internal differential amplifier provides
true remote sensing of the regulated supply’s positive and
negative output terminals as required in high current ap­plications.

The RUN/SS pin provides soft-start and optional timed,
short-circuit shutdown. Current foldback limits MOSFET
dissipation during short-circuit conditions when the
overcurrent latchoff is disabled. OPTI-LOOP compensation
allows the transient response to be optimized for a wide
range of output capacitors and ESR values.

TYPICAL APPLICATIO

0.1µF

FCB

3.3k

RUN/SS

I

TH

SGND
PGOOD

VID0–VID4

EAIN
ATTENOUT
ATTENIN
V

DIFFOUT

–

V

OS

+

V

OS

220pF

5 VID BITS

U

10µF

V

IN

TG1

SW1

BG1

PGND

TG2

SW2

BG2

S

0.47µF

S

+
–

0.47µF

CC

+
–

+

10µF

LTC3719

BOOST1

SENSE1
SENSE1

BOOST2

INTV
SENSE2
SENSE2

Figure 1. High Current Dual Phase Step-Down Converter

35V
×6

D1

1µH

D2

0.002Ω

1µH

0.002Ω

+

V

IN

5V TO 28V

V

DD_CORE

0.8V TO 1.55V
45A

C

OUT

270µF
2V

×4

3716 F01

sn3719 3719fs

1

LTC3719

WW

W

U

ABSOLUTE AXI U RATI GS

(Note 1)

Input Supply Voltage (VIN).........................36V to –0.3V

Topside Driver Voltages (BOOST1,2).........42V to –0.3V

Switch Voltage (SW1, 2) .............................36V to –5 V

SENSE1+, SENSE2+, SENSE1–,

SENSE2– Voltages ...................(1.1)INTVCC to –0.3V

EAIN, V

V

VID0–VID4, Voltages ...............................7V to –0.3V

Boosted Driver Voltage (BOOST-SW) ..........7V to –0.3V

PLLFLTR, PLLIN, V

FCB Voltages ................................... INTVCC to –0.3V

ITH Voltage................................................2.7V to –0.3V

Peak Output Current <1µs(TG1, 2, BG1, 2)................ 3A

INTVCC RMS Output Current................................ 50mA

Operating Ambient Temperature Range

(Note 2) .............................................. –40°C to 85°C

Junction Temperature (Note 3)............................. 125°C

Storage Temperature Range ................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec)..................300°C

+

–

, V

OS

, ATTENIN, ATTENOUT, PGOOD, NO_CPU,

BIAS

, EXTVCC, INTVCC, RUN/SS,

OS

DIFFOUT

,

UUW

PACKAGE/ORDER I FOR ATIO

RUN/SS
SENSE1
SENSE1

EAIN

PLLFLTR

PLLIN

FCB

I

SGND

V

DIFFOUT

V

OS

V

OS

SENSE2
SENSE2

ATTENOUT

NO_CPU

VID0
VID1

TOP VIEW

1

+

2

–

3
4
5
6
7
8

TH

9

10

–

11

+

12

–

13

+

14
15
16
17
18

G PACKAGE

36-LEAD PLASTIC SSOP

T

= 125°C, θJA = 85°C/W

JMAX

36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19

PGOOD
TG1
SW1
BOOST1
V

IN

BG1
EXTV

CC

INTV

CC

PGND
BG2
BOOST2
SW2
TG2
ATTENIN
V

BIAS

VID4
VID3
VID2

ORDER PART

NUMBER

LTC3719EG

Consult LTC Marketing for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, V

The ● denotes the specifications which apply over the full operating

BIAS

= 5V, V

= 5V unless otherwise noted.

RUN/SS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loop

V

EAIN

V

SENSEMAX

I

INEAIN

V

LOADREG

V

REFLNREG

V

FCB

I

FCB

V

BINHIBIT

Regulated Feedback Voltage ITH Voltage = 1.2V; Measured at V

(Note 4) ● 0.594 0.600 0.606 V

EAIN

Maximum Current Sense Threshold ● 62 75 88 mV
Feedback Current (Note 4) –5 –50 nA
Output Voltage Load Regulation (Note 4)

Measured in Servo Loop, ∆I
Measured in Servo Loop, ∆I

Voltage: 1.2V to 0.7V ● 0.1 0.5 %

TH

Voltage: 1.2V to 2V ● –0.1 –0.5 %

TH

Reference Voltage Line Regulation VIN = 3.6V to 30V (Note 4) 0.002 0.02 %/V
Forced Continuous Threshold ● 0.57 0.6 0.63 V
Forced Continuous Current – 0.17 –1 µA
Burst Inhibit (Constant Frequency) Measured at FCB pin 4.3 4.8 V

Threshold

V

OVL

Output Overvoltage Threshold Measured at V

EAIN

● 0.64 0.66 0.68 V

UVLO Undervoltage Lockout VIN Ramping Down 3 3.33 4 V
g
g

m

mOL

Transconductance Amplifier g

m

ITH = 1.2V, Sink/Source 5µA (Note 4) 3 mmho

Transconductance Amplifier Gain ITH = 1.2V, (gm • ZL; No Ext Load) (Note 4) 1.5 V/mV

2

sn3719 3719fs

LTC3719

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, V

The ● denotes the specifications which apply over the full operating

BIAS

= 5V, V

= 5V unless otherwise noted.

RUN/SS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

Q

Input DC Supply Current (Note 5)

Normal Mode 1.2 mA

I

RUN/SS

V

RUN/SS

V

RUN/SSLO

I

SCL

I

SDLHO

I

SENSE

DF

MAX

Shutdown V
Soft-Start Charge Current V
RUN/SS Pin ON Threshold V
RUN/SS Pin Latchoff Arming V
RUN/SS Discharge Current Soft Short Condition V
Shutdown Latch Disable Current V
Total Sense Pins Source Current Each Channel: V
Maximum Duty Factor In Dropout 98 99.5 %

= 0V 20 40 µA

RUN/SS

= 1.9V –0.5 –1.2 µA

RUN/SS

Rising 1.0 1.5 1.9 V

RUN/SS

Rising from 3V 4.1 4.5 V

RUN/SS

= 0.5V, V

EAIN

= 0.5V 1.6 5 µA

EAIN

SENSE1–, 2

– = V

SENSE1+, 2

= 4.5V 0.5 2 4 µA

RUN/SS

+ = 0V –85 –60 µA

Top Gate Transition Time: (Note 6)

TG1, 2 t
TG1, 2 t

Rise Time C

r

Fall Time C

f

= 3300pF 30 90 ns

LOAD

= 3300pF 40 90 ns

LOAD

Bottom Gate Transition Time: (Note 6)

BG1, 2 t
BG1, 2 t

TG/BG t

Rise Time C

r

Fall Time C

f

Top Gate Off to Bottom Gate On Delay C

1D

= 3300pF 30 90 ns

LOAD

= 3300pF 20 90 ns

LOAD

= 3300pF Each Driver (Note 6) 90 ns

LOAD

Synchronous Switch-On Delay Time

BG/TG t

Bottom Gate Off to Top Gate On Delay C

2D

= 3300pF Each Driver (Note 6) 90 ns

LOAD

Top Switch-On Delay Time

t

ON(MIN)

Minimum On-Time Tested with a Square Wave (Note 7) 180 ns

Internal VCC Regulator

V

INTVCC

V

LDO

V

LDO

V

EXTVCC

V

LDOHYS

Internal VCC Voltage 6V < VIN < 30V, V

INT INTVCC Load Regulation ICC = 0 to 20mA, V
EXT EXTVCC Voltage Drop ICC = 20mA, V

EXTVCC

EXTVCC Switchover Voltage ICC = 20mA, EXTV
EXTVCC Switchover Hysteresis ICC = 20mA, EXTV

= 4V 4.8 5.0 5.2 V

EXTVCC

= 4V 0.2 1.0 %

EXTVCC

= 5V 80 160 mV
Ramping Positive ● 4.5 4.7 V

CC

Ramping Negative 0.2 V

CC

VID Parameters

V

BIAS

R

ATTEN

Operating Supply Voltage Range 2.7 5.5 V
Resistance Between ATTENIN 10 kΩ

and ATTENOUT Pins

ATTEN
R

PULLUP

VID

THLOW

VID

THHIGH

VID

LEAK

V

NO_CPU

Resistive Divider Error ● – 0.35 0.25 %

ERR

VID0 to VID4 Pull-Up Resistance (Note 8) 40 kΩ
VID0 to VID4 Logic Threshold Low 0.4 V
VID0 to VID4 Logic Threshold High 1.6 V
VID0 to VID4 Leakage V
NO_CPU Maximum Output Voltage I

< VID0–VID4 < 7V ±1 µA

BIAS

= 2mA 0.4 V

NO_CPU

sn3719 3719fs

3

LTC3719

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, V

The ● denotes the specifications which apply over the full operating

BIAS

= 5V, V

= 5V unless otherwise noted.

RUN/SS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Oscillator and Phase-Locked Loop

f

NOM

f

LOW

f

HIGH

R

PLLIN

I

PLLFLTR

R

RELPHS

Nominal Frequency V
Lowest Frequency V
Highest Frequency V

= 1.2V 190 220 250 kHz

PLLFLTR

= 0V 120 140 160 kHz

PLLFLTR

≥ 2.4V 280 310 360 kHz

PLLFLTR

PLLIN Input Resistance 50 kΩ
Phase Detector Output Current

Sinking Capability f

Sourcing Capability f

PLLIN
PLLIN

< f
> f

OSC
OSC

–15 µA

15 µA

Controller 2-Controller 1 Phase 180 Deg

PGOOD Output

V

PGL

I

PGOOD

V

PG

PGOOD Voltage Low I
PGOOD Leakage Current V
PGOOD Trip Level, Either Controller V

= 2mA 0.1 0.3 V

PGOOD

= 5V ±1 µA

PGOOD

with Respect to Set Output Voltage

EAIN

Ramping Negative –8 – 10 – 12 %

V

EAIN

Ramping Positive 8 10 12 %

V

EAIN

Differential Amplifier/Op Amp Gain Block

A

DA

CMRR
R

IN

Differential Amplifier Gain V
Common Mode Rejection Ratio 0V < VCM < 5V; V

DA

= 0V 0.995 1 1.005 V/V

AMPMD

Input Resistance Measured at VOS+ Input; V

= 0V 46 55 dB

AMPMD

= 0V 80 kΩ

AMPMD

Note 1: Absolute Maximum Ratings are those values beyond which the
life of a device may be impaired.

Note 2: The LTC3719EG is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.

Note 3: T
dissipation P

is calculated from the ambient temperature TA and power

J

according to the following formula:

D

LTC3719EG: TJ = TA + (PD • 85°C/W)

Note 4: The LTC3719 is tested in a feedback loop that servos V
specified voltage and measures the resultant V

EAIN

.

ITH

to a

Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.

Note 6: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.

Note 7: The minimum on-time condition corresponds to the on inductor
peak-to-peak ripple current ≥40% I

(see Minimum On-Time

MAX

Considerations in the Applications Information section).
Note 8: Each built-in pull-up resistor attached to the VID inputs also has a

series diode to allow input voltages higher than the VIDV

supply without

CC

damage or clamping (see the Applications Information section).

4

sn3719 3719fs

UW

TEMPERATURE (

°C)

–50

INTV

CC

AND EXTV

CC

SWITCH VOLTAGE (V)

4.95

5.00

5.05

25 75

3719 G06

4.90

4.85

–25 0

50 100 125

4.80

4.70

4.75

INTVCC VOLTAGE

EXTVCC SWITCHOVER THRESHOLD

TYPICAL PERFOR A CE CHARACTERISTICS

LTC3719

Efficiency vs Load Current
(3 Operating Modes) (Figure 12)

100

Burst Mode

90

OPERATION

80
70
60
50
40

EFFICIENCY (%)

30
20
10

0

0.01

FORCED
CONTINUOUS
MODE

CONSTANT
FREQUENCY
(BURST DISABLED)

0.1

1

LOAD CURRENT (A)

V

= 5V

IN

V

= 1.55V

OUT

FREQ = 200kHz

3719 G01

10010

Efficiency vs Load Current
(Figure 12)

100

80

60

40

EFFICIENCY (%)

20

0

0.1

Supply Current vs Input Voltage
and Mode EXTVCC Voltage Drop

1000

800

600

ON

250

200

150

VIN = 5V
VIN = 8V
VIN = 12V
VIN = 20V

V

= 1.55V

OUT

V

= 0V

EXTVCC

FREQ = 200kHz

= 0V

V

FCB

1 10 100

LOAD CURRENT (A)

3719 G02

Efficiency vs Input Voltage
(Figure 12)

100

I

= 20A

OUT

= 1.55V

V

OUT

90

80

70

EFFICIENCY (%)

60

50

5

10

INPUT VOLTAGE (V)

INTVCC and EXTVCC Switch
Voltage vs Temperature

15

20

3719 G03

400

SUPPLY CURRENT (µA)

200

0

05

5.1

5.0

4.9

4.8

VOLTAGE (V)

4.7

CC

INTV

4.6

4.5

4.4
0

10

INPUT VOLTAGE (V)

I

= 1mA

LOAD

510

INPUT VOLTAGE (V)

SHUTDOWN

20

15

20 30 35

15 25

100

VOLTAGE DROP (mV)

CC

EXTV

50

0

10

30

35

3719 G04

25

0

CURRENT (mA)

30

40

20

50

3719 G05

Maximum Current Sense Threshold
vs Percent of Nominal Output
Voltage (Foldback)Internal 5V LDO Line Reg

80

70

60

50

(mV)

40

SENSE

V

30

20

10

0

0

25

PERCENT OF NOMINAL OUTPUT VOLTAGE (%)

50

75

3719 G09

sn3719 3719fs

100

3719 G07

Maximum Current Sense Threshold
vs Duty Factor

75

50

(mV)

SENSE

V

25

0

0

20 40 60 80

DUTY FACTOR (%)

100

3719 G08

5

LTC3719

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Maximum Current Sense Threshold

(mV)

SENSE

V

20

80

60

40

0

vs V

V

SENSE(CM)

0

(Soft-Start)

RUN/SS

= 1.55V

1234

V

(V)

RUN/SS

56

3719 G10

Load Regulation V

0.0

–0.1

(%)

OUT

–0.2

NORMALIZED V

–0.3

FCB = 0V

= 15V

V

IN

FIGURE 1

Maximum Current Sense Threshold
vs Sense Common Mode Voltage

80

76

72

(mV)

SENSE

68

V

64

60

(V)

ITH

V

2.5

2.0

1.5

1.0

0.5

0

COMMON MODE VOLTAGE (V)

vs V

ITH

RUN/SS

V

= 0.7V

OSENSE

1

(Soft-Start)

3719 G11

Current Sense Threshold
vs ITH Voltage

90
80
70
60
50
40

(mV)

30

20

SENSE

V

10

0
–10
–20

2

–30

0.5

0

1.5

2

1

V

(V)

ITH

2.5

3719 G12

SENSE Pins Total Source Current

100

50

(µA)

0

SENSE

I

–50

–0.4

5

0

10

LOAD CURRENT (A)

Maximum Current Sense
Threshold vs Temperature

80

78

76

(mV)

SENSE

74

V

72

70

–50 –25

25

0

TEMPERATURE (°C)

15

20

25

3719 G13

0

0

234

1

V

RUN/SS

(V)

56

3719 G14

RUN/SS Current vs Temperature

1.8

1.6

1.4

1.2

1.0

0.8

0.6

RUN/SS CURRENT (µA)

0.4

0.2

50

75

100

125

3719 G16

0

–50 –25

0 25 125

TEMPERATURE (°C)

75 10050

3719 G17

–100

0

V

COMMON MODE VOLTAGE (V)

SENSE

Soft-Start Up (Figure 12)

V

ITH

1V/DIV

V

OUT

1V/DIV

V

RUN/SS

2V/DIV

1

3719 G15

100ms/DIV 3718 G18

sn3719 3719fs

2

6

UW

TEMPERATURE (

°C)

–50

200

250

350

25 75

3719 G22

150

100

–25 0

50 100 125

50

0

300

FREQUENCY (kHz)

V

PLLFLTR

= 2.4V

V

PLLFLTR

= 0V

TYPICAL PERFOR A CE CHARACTERISTICS

Load Step (Figure 12)

Burst Mode Operation (Figure 12)

LTC3719

Constant Frequency Mode
(Figure 12)

V

OUT(AC)

50mV/DIV

I

LOAD

10A/DIV

VIN = 12V, V

OUT

= 1.25V

200µs/DIV

Current Sense Pin Input Current
vs Temperature

–12

V

= 1.55V

OUT

–11

–10

–9

–8

CURRENT SENSE INPUT CURRENT (µA)

–7

–50 –25

0

TEMPERATURE (°C)

50

25

VIN = 12V, V

V

OUT(AC)

I

L1

5A/DIV

I

L2

5A/DIV

FCB = INTV

Oscillator Frequency
vs Temperature

3719 G19

V

OUT(AC)

50mV/DIV

I

5A/DIV

I

5A/DIV

VIN = 12V, V

L1

L2

FCB = OPEN

= 1.55V, I

OUT

LOAD

10µs/DIV

= 3A

50mV/DIV

R5, R7 = 2mΩ R5, R7 = 2mΩ

3719 G25

EXTVCC Switch Resistance
vs Temperature

10

8

6

4

SWITCH RESISTANCE (Ω)

CC

2

EXTV

100

125

3719 G20

75

0

–50 –25

50

25

0

TEMPERATURE (°C)

100

125

3719 G21

75

OUT

CC

= 1.55V, I

10µs/DIV

LOAD

= 3A

3719 G26

Undervoltage Lockout
vs Temperature

3.50

3.45

3.40

3.35

3.30

UNDERVOLTAGE LOCKOUT (V)

3.25

3.20
–50

–25 0

50 100 125

25 75

TEMPERATURE (°C)

3719 G23

V

Shutdown Latch

RUN/SS

Thresholds vs Temperature

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

SHUTDOWN LATCH THRESHOLDS (V)

0

–50 –25

LATCH ARMING

LATCHOFF

THRESHOLD

0 25 125

TEMPERATURE (°C)

75 10050

3719 G24

sn3719 3719fs

7

LTC3719

UUU

PI FU CTIO S

RUN/SS (Pin 1): Combination of Soft-Start, Run Control
Input and Short-Circuit Detection Timer. A capacitor to
ground at this pin sets the ramp time to full current output.
Forcing this pin below 0.8V causes the IC to shut down all
internal circuitry. All functions are disabled in shutdown.

SENSE1+, SENSE2+ (Pins 2,14): The (+) Input to Each
Differential Current Comparator. The ITH pin voltage and
built-in offsets between SENSE– and SENSE+ pins in
conjunction with R

SENSE1–, SENSE2– (Pins 3,13): The (–) Input to the
Differential Current Comparators.

EAIN (Pin 4): Input to the error amplifier that compares the
feedback voltage to the internal 0.6V reference voltage.
This pin is normally connected to a resistive divider from
the output of the differential amplifier (DIFFOUT).

PLLFLTR (Pin 5): The phase-locked loop’s lowpass filter
is tied to this pin. Alternatively, this pin can be driven with
an AC or DC voltage source to vary the frequency of the
internal oscillator. Do not apply voltage to this pin prior to
application of VIN.

set the current trip threshold.

SENSE

ITH (Pin 8): Error Amplifier Output and Switching Regula­tor Compensation Point. Both current comparator’s thresh­olds increase with this control voltage. The normal voltage
range of this pin is from 0V to 2.4V

SGND (Pin 9): Signal Ground. This pin is common to both
controllers. Route separately to the PGND pin.

V

DIFFOUT

pin provides true remote output voltage sensing. V
normally drives an external resistive divider that sets the
output voltage.

V

OS

fier. Internal precision resistors configure it as a differen­tial amplifier whose output is V

ATTENOUT (Pin 15): Voltage Feedback Signal Resistively
Divided According to the VID Programming Code.

NO_CPU (Pin 16): Open-Drain Logic Output. NO_CPU is
pulled to ground if VID0 to VID3 are all high.

VID0–VID4 (Pins 17,18, 19, 20, 21): VID Control Logic
Input Pins.

(Pin 10): Output of a Differential Amplifier. This

–

+

, V

(Pins 11, 12): Inputs to an Operational Ampli-

OS

DIFFOUT

.

DIFFOUT

PLLIN (Pin 6): External Synchronization Input to Phase
Detector. This pin is internally terminated to SGND with
50kΩ. The phase-locked loop will force the rising top gate
signal of controller 1 to be synchronized with the rising
edge of the PLLIN signal.

FCB (Pin 7): Forced Continuous Control Input. This input
acts on both output stages. Pulling this pin below 0.6V
will force continuous synchronous operation. Do not
leave this pin floating without a decoupling capacitor.

V

(Pin 22): Supply Pin for the VID Control Circuit.

BIAS

ATTENIN (Pin 23): The Input to the VID Controlled Resis-

tive Divider.
TG2, TG1 (Pins 24, 35): High Current Gate Drives for Top

N-Channel MOSFETS. These are the outputs of floating
drivers with a voltage swing equal to INTVCC superim­posed on the switch node voltage SW.

8

sn3719 3719fs

UUU

PI FU CTIO S

LTC3719

SW2, SW1 (Pins 25, 34): Switch Node Connections to
Inductors. Voltage swing at these pins is from a Schottky
diode (external) voltage drop below ground to VIN.

BOOST2, BOOST1 (Pins 26, 33): Bootstrapped Supplies
to the Topside Floating Drivers. External capacitors are con­nected between the BOOST and SW pins, and Schottky
diodes are connected between the BOOST and INTVCC pins.

BG2, BG1 (Pins 27, 31): High Current Gate Drives for
Bottom N-Channel MOSFETS. Voltage swing at these pins
is from ground to INTVCC.

PGND (Pin 28): Driver Power Ground. Connect to sources
of bottom N-channel MOSFETS and the (–) terminals of CIN.

INTVCC (Pin 29): Output of the Internal 5V Linear Low
Dropout Regulator and the EXTVCC Switch. The driver and

control circuits are powered from this voltage source.
Decouple to power ground with a 1µF ceramic capacitor
placed directly adjacent to the IC and minimum of 4.7µF
additional tantalum or other low ESR capacitor.

EXTVCC (Pin 30): External Power Input to an Internal
Switch. This switch closes and supplies INTV
ing the internal low dropout regulator whenever EXTVCC is
higher than 4.7V. See EXTVCC Connection in the Applica­tions Information section. Do not exceed 7V on this pin
and ensure V

VIN (Pin 32): Main Supply Pin. Should be closely de­coupled to the IC’s signal ground pin.

PGOOD (Pin 36): Open-Drain Logic Output. PGOOD is
pulled to ground when the voltage on the EAIN pin is not
within ±10% of its set point.

EXTVCC

≤ V

INTVCC

.

bypass-

CC,

sn3719 3719fs

9

LTC3719

UU

W

FU CTIO AL DIAGRA

f

IN

V

V

DIFFOUT

OS

OS

R

LP

C

LP

–

+

5V

+

PLLIN

PLLFLTR

PGOOD

FCB

V

EXTV

INTV

SGND

ATTENIN

ATTENOUT

0.18µA

IN

CC

CC

50k

PHASE DET

OSCILLATOR

40k

40k

3V

4.8V

10k

0.60V

4.5V

R1

CLK1
CLK2

TO SECOND
CHANNEL

–

0.66V

+

EAIN

–
+

0.54V

40k

–

A1

+

40k

–
+

+

FCB

–

V

REF

+

–

5V
LDO
REG

INTERNAL

SUPPLY

DUPLICATE FOR SECOND
CONTROLLER CHANNEL

0.86V
5V

FB

SLOPE

COMP

1.2µA

6V

5-BIT VID DECODER

SRQ

0.55V

I

1

DROP

OUT
DET

Q

+
–

–

+

45k

TYPICAL ALL

VID PINS

40k

B

+–

SHDN

BOT FCB

+–

RST

5V

FB

TOP ON

SHDN

–
+

45k

2.4V

OV

RUN

SOFT-

START

I

2

EA

SWITCH

LOGIC

–
+

+
–

INTV

BOOST

CC

INTV

30k

30k

CC

TG

SW

BG

PGND

SENSE

SENSE

EAIN

I

TH

RUN/SS

+

–

TOP

BOT

INTV

V

FB

0.60V

0.66V

V

CC

IN

D

B

C

B

L

C

C

C

R

C2

C

C

SS

R

D1

SENSE

+

C

IN

C

OUT

+

V

OUT

21

43

10

NO_CPU

VID0

VID1 VID2 VID3 VID4

V

BIAS

3719 FBD

sn3719 3719fs