Linear Technology LTC3813EG, LTC3813 Datasheet

LTC3813

100V Current Mode

Synchronous Step-Up Controller

FEATURES

n

High Output Voltages: Up to 100V

n

Large 1Ω Gate Drivers

n

No Current Sense Resistor Required

n

Dual N-Channel MOSFET Synchronous Drive

n

±0.5% 0.8V Voltage Reference

n

Fast Transient Response

n

Programmable Soft-Start

n

Generates 10V Driver Supply from Input Supply

n

Synchronizable to External Clock

n

Power Good Output Voltage Monitor

n

Adjustable Off-Time/Frequency: t

n

Adjustable Cycle-by-Cycle Current Limit

n

Programmable Undervoltage Lockout

n

Output Overvoltage Protection

n

28-Pin SSOP Package

OFF(MIN)

< 100ns

APPLICATIONS

n

24V Fan Supplies

n

48V Telecom and Base Station Power Supplies

n

Networking Equipment, Servers

n

Automotive and Industrial Control Systems

DESCRIPTION

The LTC3813 is a synchronous step-up switching regulator
controller that can generate output voltages up to 100V.
The LTC3813 uses a constant off-time peak current control
architecture with accurate cycle-by-cycle current limit,
without requiring a sense resistor.

A precise internal reference provides ±0.5% DC accuracy.
A high bandwidth (25MHz) error amplifi er provides very
fast line and load transient response. Large 1Ω gate drivers
allow the LTC3813 to drive multiple MOSFETs for higher
current applications. The operating frequency is selected
by an external resistor and is compensated for variations

and can also be synchronized to an external clock

in V

IN

for switching-noise sensitive applications. A shutdown pin
allows the LTC3813 to be turned off, reducing the supply
current to 240μA.

PARAMETER LTC3813 LTC3814-5

Maximum V

OUT

MOSFET Gate Drive 6.35V to 14V 4.5V to 14V

+

UV

INTV

CC

–

UV

INTV

CC

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 5481178, 5847554, 6304066, 6476589, 6580258, 6677210, 6774611.

100V 60V

6.2V 4.2V

6V 4V

TYPICAL APPLICATION

High Effi ciency High Voltage Step-Up Converter

500k

V

OUT

1000pF

0.01

100pF

I

OFF

PGOOD

V

RNG

SYNC

SS

SHDN

I

100k

TH

V

FB

SGND

μ

F

LTC3813

BOOST

EXTV

DRV

INTV

SENSE

SENSE

BGRTN

NDRV

TG

SW

CC

CC

CC

+

BG

–

50k

0.1μF

Effi ciency vs Load Current

100

V

IN

22

30.9k

499

μ

Ω

3813 TA01

10V TO 40V

F

+

V

OUT

50V/5A

270μF

× 2

95

90

EFFICIENCY (%)

85

80

04

VIN = 12V

123 5

LOAD (A)

M1
Si7850DP

+

10

μ

H

D1
MBR1100

M2
Si7850DP

× 2

1

μ

F

VIN = 36V

VIN = 24V

3813 TA01b

3813fa

1

LTC3813

ABSOLUTE MAXIMUM RATINGS

(Note 1)

Supply Voltages
INTV
(DRV

BOOST ................................................ –0.3V to 114V

BGRTN ....................................................... –5V to 0V

EXTV
(NDRV - INTV
SW, SENSE
I

OFF

SS Voltage ................................................... –0.3V to 5V

PGOOD Voltage ............................................ –0.3V to 7V

V

RNG

UVIN Voltages ........................................ –0.3V to 14V

PLL/LPF, FB Voltages ................................. –0.3V to 2.7V

TG, BG, INTV

Operating Temperature Range (Note 2).... –40°C to 85°C

Junction Temperature (Notes 3, 7)........................ 125°C

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

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

, DRVCC ...................................... –0.3V to 14V

CC

- BGRTN), (BOOST - SW) ......... –0.3V to 14V

CC

.................................................. –0.3V to 15V

CC

) Voltage ........................... –0.3V to 10V

CC

+

Voltage ................................... –1V to 100V

Voltage .............................................. –0.3V to 100V

, V

, SYNC, SHDN,

OFF

, EXTVCC RMS Currents .................50mA

CC

PIN CONFIGURATION

TOP VIEW

I

1

OFF

NC

2

NC

3

V

4

OFF

V

5

RNG

PGOOD

6

SYNC

7

I

8

TH

V

9

FB

PLL/LPF

10

SS

11

SGND

12

SHDN

13

UVIN

14

G PACKAGE

28-LEAD PLASTIC SSOP

T

= 125°C, θJA = 100°C/W

JMAX

28

27

26

25

24

23

22

21

20

19

18

17

16

15

BOOST

TG

SW

SENSE

NC

NC

NC

SENSE

BGRTN

BG

DRV

CC

INTV

EXTV

NDRV

+

–

CC

CC

ORDER INFORMATION

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

LTC3813EG#PBF LTC3813EG#TRPBF LTC3813EG 28-Lead Plastic SSOP –40°C to 85°C

Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based fi nish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/

The

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifi cations are at TA = 25°C, INTVCC = DRVCC = V
V

NDRV

= 10V, V

SYNC

= V

SENSE

+

= V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Main Control Loop

INTV

I

Q

I

BOOST

V

FB

CC

INTVCC Supply Voltage

INTVCC Supply Current
INTV

Shutdown Current

CC

BOOST Supply Current (Note 5)

Feedback Voltage (Note 4)

SENSE

–

= V

= VSW = 0V, unless otherwise specifi ed.

BGRTN

l denotes specifi cations which apply over the full operating

= V

= V

= SHDN = UVIN = V

RNG

l

6.35 14 V

3

240

SHDN > 1.5V, I
SHDN = 0V

= 9.5V (Note 5)

NTVCC

BOOST

OFF

270

SHDN = 0V

0°C to 85°C
–40°C to 85°C

0.796

l

0.794

l

0.792

0

0.800

0.800

0.800

EXTVCC

6

600

400

5

0.804

0.806

0.806

=

mA

μA

μA
μA

V
V
V

2

3813fa

LTC3813

ELECTRICAL CHARACTERISTICS

The l denotes specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
V

NDRV

= 10V, V

SYNC

= V

SENSE

+

= V

SENSE

–

= V

BGRTN

= 25°C, INTVCC = DRVCC = V

A

= V

= 0V, unless otherwise specifi ed.

SW

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

ΔV

FB,LINE

V

SENSE(MAX)

V

SENSE(MIN)

I

VFB

(EA) Error Amplifi er DC Open Loop Gain 65 100 dB

A

VOL

f

U

I

SYNC

V

SHDN

I

SHDN

I

SS

V

VINUV

Feedback Voltage Line Regulation 7V < INTVCC < 14V (Note 4)

Maximum Current Sense Threshold V

Minimum Current Sense Threshold V

= 2V, VFB = 0.76V

RNG

V

= 0V, VFB = 0.76V

RNG

V

= INTVCC, VFB = 0.76V

RNG

= 2V, VFB = 0.84V

RNG

V

= 0V, VFB = 0.84V

RNG

V

= INTVCC, VFB = 0.84V

RNG

Feedback Current VFB = 0.8V 20 150 nA

Error Amp Unity Gain Crossover Frequency (Note 6) 25 MHz

SYNC Current 01 μA

Shutdown Threshold 1.2 1.5 2 V
SHDN Pin Input Current 01 μA

SS Source Current VSS > 0.5V 0.7 1.4 2.5 μA

VIN Undervoltage Lockout VIN Rising

V

Falling

IN

Hysteresis

V

VCCUV

INTVCC Undervoltage Lockout INTVCC Rising

Hysteresis

Oscillator and Phase-Locked Loop

t

OFF

t

OFF(MIN)

t

ON(MIN)

t

OFF(PLL)

I

PLL/LPF

Off-Time I

Minimum Off-Time I

Minimum On-Time 250 ns

t

Modulation Range by PLL

OFF

Down Modulation
Up Modulation

Phase Detector Output Current

Sinking Capability
Sourcing Capability

= 100μA

OFF

I

= 300μA

OFF

= 2000μA 100 ns

OFF

I

= 100μA, V

OFF

I

= 100μA, V

OFF

f

< f

PLLIN

f

> f

PLLIN

SW
SW

PLL/LPF
PLL/LPF

= 0.6V
= 1.8V

Driver

I

BG,PEAK

R

BG,SINK

I

TG,PEAK

R

TG,SINK

BG Driver Peak Source Current VBG = 0V 1.5 2 A

BG Driver Pulldown R

DS(ON)

TG Driver Peak Source Current VTG – VSW = 0V 1.5 2 A

TG Driver Pulldown R

DS(ON)

PGOOD Output

ΔV

FBOV

PGOOD Upper Threshold
PGOOD Lower Threshold

ΔV

FB,HYST

V

PGOOD

I

PGOOD

PGOOD Hysteresis VFB Returning 1.5 3 %

PGOOD Low Voltage I

PGOOD Leakage Current V

PG Delay PGOOD Delay V

VFB Rising
V

Falling

FB

= 5mA 0.3 0.6 V

PGOOD

= 5V 0 2 μA

PGOOD

Falling 125 μs

FB

BOOST

= V

OFF

= V

= SHDN = UVIN = V

RNG

l

256

70

170

l

0.86

l

0.78

0.07

l

6.05 6.2

1.55
515

2.2

0.6

7.5

–7.5

=

EXTVCC

0.002 0.02 %/V

320

95

215

–300

–85

–200

0.88

0.80

0.10

384
120
260

0.92

0.82

0.12

mV
mV
mV

mV
mV
mV

6.35 V

0.2

1.85
605

3.6

1.2

15

–25

2.15
695

5

1.8

μA
μA

11.5

11.5

10

–10

12.5

–12.5

V
V
V

V

μs
ns

μs
μs

Ω

Ω

%
%

3813fa

3

LTC3813

ELECTRICAL CHARACTERISTICS

The l denotes specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
V

NDRV

= 10V, V

SYNC

= V

SENSE

+

= V

SENSE

–

= V

BGRTN

= 25°C, INTVCC = DRVCC = V

A

= V

= 0V, unless otherwise specifi ed.

SW

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Regulators

V

CC

V

EXTVCC

V

INTVCC,1

ΔV

EXTVCC,1

ΔV

LOADREG,1

V

INTVCC,2

ΔV

LOADREG,2

I

NDRV

V

CCSR

I

CCSR

EXTVCC Switchover Voltage

EXTV

Rising

CC

EXTV

Hysteresis

CC

INTVCC Voltage from EXTV

V

EXTVCC

- V

at Dropout ICC = 20mA, V

INTVCC

CC

INTVCC Load Regulation from EXTV

CC

10.5V < V

I

CC

EXTVCC

= 0mA to 20mA, V

< 15V 9.4 10 10.6 V

= 9.1V 170 250 mV

EXTVCC

EXTVCC

INTVCC Voltage from NDRV Regulator Linear Regulator in Operation 9.4 10 10.6 V

INTVCC Load Regulation from NDRV ICC = 0mA to 20mA, V

Current into NDRV Pin V

NDRV

– V

INTVCC

EXTVCC

= 3V 20 40 60 μA

Maximum Supply Voltage Trickle Charger Shunt Regulator 15 V

Maximum Current into NDRV/INTV

CC

Trickle Charger Shunt Regulator,
INTV

≤ 16.7V (Note 8)

CC

= V

= V

BOOST

OFF

= SHDN = UVIN = V

RNG

l

6.4

0.1

6.7

0.25 0.5

EXTVCC

=

= 12V 0.01 %

= 0 0.01 %

10 mA

V
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.

Note 2: The LTC3813E is guaranteed to meet performance specifi cations
from 0°C to 85°C. Specifi cations 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

LTC3813: T
Note 4: The LTC3813 is tested in a feedback loop that servos V

reference voltage with the I

is calculated from the ambient temperature TA and power

J

according to the following formula:

D

= TA + (PD • 100°C/W)

J

pin forced to a voltage between 1V and 2V.

TH

FB

to the

Note 5: The dynamic input supply current is higher due to the power
MOSFET gate charging being delivered at the switching frequency
(Q

• fSW).

G

Note 6: Guaranteed by design. Not subject to test.
Note 7: This IC includes overtemperature protection that is intended

to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specifi ed maximum operating junction
temperature may impair device reliability.

Note 8: I

is the sum of current into NDRV and INTVCC.

CC

4

3813fa

LTC3813

TYPICAL PERFORMANCE CHARACTERISTICS

Load Transient Response Start-Up

V

OUT

200mV/

DIV

I

OUT

2A/DIV

FIGURE 14 CIRCUIT

= 12V

V

IN

0A TO 4A LOAD STEP

Effi ciency vs Load Current

100

V

= 24V

OUT

95

90

EFFICIENCY (%)

85

80

0

1

100μs/DIV

VIN = 12V

VIN = 5V

2

LOAD (A)

3813 G01

3

3813 G04

4

V

OUT

20V/DIV

SS

4V/DIV

I

L

5A/DIV

FRONT PAGE CIRCUIT

= 24V

V

IN

= 2A

I

LOAD

Frequency vs Input Voltage

300

FRONT PAGE CIRCUIT

280

260

240

FREQUENCY (kHz)

220

200

15

10

INPUT VOLTAGE (V)

20

1ms/DIV

25

I

LOAD

I

LOAD

30 35

= 0A

= 1A

3813 G02

3813 G05

40

Overcurrent Operation

V

OUT

20V/DIV

I

L

5A/DIV

FRONT PAGE CIRCUIT

= 24V

V

IN

= 1Ω

R

SHORT

Frequency vs Load Current

280

FRONT PAGE CIRCUIT

270

260

250

240

230

FREQUENCY (kHz)

220

210

200

0

1

LOAD CURRENT (A)

500μs/DIV

VIN = 12V

2

VIN = 24V

3

3813 G03

4

3813 G06

Current Sense Threshold

Voltage

vs I

TH

400

300

200

100

0

–100

–200

CURRENT SENSE THRESHOLD (mV)

–300

–400

0

0.5

1 1.5 2

ITH VOLTAGE (V)

V

RNG

1.4V

1V

0.7V

0.5V

2.5 3

= 2V

3813 G07

Off-Time vs I

10000

1000

OFF-TIME (ns)

100

10

10

Current

OFF

V

= INTV

OFF

CC

100 1000 10000
I

CURRENT (μA)

OFF

3813 G08

Off-Time vs V

700

I

OFF

600

500

400

300

OFF-TIME (ns)

200

100

0

0

= 300μA

0.5 1

Voltage

OFF

1.5 2.5

V

VOLTAGE (V)

OFF

23

3813 G09

3813fa

5

LTC3813

TYPICAL PERFORMANCE CHARACTERISTICS

Off-Time vs Temperature

680

I

= 300μA

OFF

660

640

620

OFF-TIME (ns)

600

580

560

–50

–25 0

25 75

TEMPERATURE (°C)

Feedback Reference Voltage
vs Temperature

0.803

0.802

0.801

0.800

0.799

REFERENCE VOLTAGE (V)

0.798

50 100 125

3813 G10

Maximum Current Sense
Threshold vs V

400

300

200

100

MAXIMUM CURRENT SENSE THRESHOLD (mV)

0

0.5
V

Voltage

RNG

1 1.5

VOLTAGE (V)

RNG

Driver Peak Source Current
vs Temperature

2.5
V

= V

INTVCC

= 10V

BOOST

2.0

1.5

PEAK SOURCE CURRENT (A)

3813 G11

Maximum Current Sense
Threshold vs Temperature

230

V

= INTV

RNG

220

210

200

190

MAXIMUM CURRENT SENSE THRESHOLD (mV)

180

2

–50 –25

CC

25

0

TEMPERATURE (°C)

Driver Pulldown R
vs Temperature

1.50
V

= V

INTVCC

= 10V

1.25

1.00

(Ω)

0.75

DS(ON)

R

0.50

0.25

BOOST

50

DS(ON)

100

125

3813 G12

75

6

0.797
–50 –25

50

25

0

TEMPERATURE (°C)

Driver Peak Source Current
vs Supply Voltage

3.0

2.5

2.0

1.5

1.0

PEAK SOURCE CURRENT (A)

0.5

0

56 8 10 12 14

75

125

100

3813 G13

7 9 11 13

DRVCC/BOOST VOLTAGE (V)

1

–25 0 25 50

–50

15

3813 G16

TEMPERATURE (°C)

(Ω)

R

75 100 125

3813 G14

Driver Pulldown R
vs Supply Voltage

1.1

1.0

0.9

DS(ON)

0.8

0.7

0.6
79

8

6

DRVCC/BOOST VOLTAGE (V)

0

–50

–25 0

DS(ON)

11 15

12

10

25 75

TEMPERATURE (°C)

13

14

3813 G17

50 100 125

3813 G15

3813fa

TYPICAL PERFORMANCE CHARACTERISTICS

LTC3813

EXTVCC LDO Resistance at
Dropout vs Temperature

14

12

10

8

6

RESISTANCE (Ω)

4

2

0

–25 0 50

–50

25

TEMPERATURE (°C)

INTVCC Current vs INTVCC Voltage

4.0

3.5

3.0

2.5

2.0

CURRENT (mA)

1.5

CC

INTV

1.0

0.5

0

0

24

INTVCC VOLTAGE (V)

81214

610

75 100 125

3813 G18

3813 G21

INTV

Current vs Temperature

CC

4

3

2

CURRENT (mA)

CC

INTV

1

0

–50 –25

25

0

TEMPERATURE (°C)

INTVCC Shutdown Current
vs INTVCC Voltage

300

250

200

150

CURRENT (μA)

CC

100

INTV

50

0

0

24

610

INTVCC VOLTAGE (V)

50

75

81214

100

125

3813 G19

3813 G22

Shutdown Current

INTV

CC

vs Temperature

400

300

200

CURRENT (μA)

CC

INTV

100

0

–25 0 50

–50

SS Pull-Up Current
vs Temperature

3

2

1

SS CURRENT (μA)

0

–50

–25 0

25

TEMPERATURE (°C)

50 100 125

25 75

TEMPERATURE (°C)

75 100 125

3813 G20

3813 G23

ITH Voltage
vs Load Current

3

FRONT PAGE CIRCUIT

= 24V

V

IN

V

RNG

2

VOLTAGE (V)

TH

I

1

0

0

= 1V

1234

LOAD CURRENT (A)

3813 G24

Shutdown Threshold
vs Temperature

2.2

2.0

1.8

1.6

1.4

1.2

1.0

SHUTDOWN THRESHOLD (V)

0.8

0.6
–25 0 50

–50

25

TEMPERATURE (°C)

75 100 125

3813 G25

3813fa

7

LTC3813

PIN FUNCTIONS

I

(Pin 1): Off-Time Current Input. Tie a resistor from

OFF

to this pin to set the one-shot timer current and

V

OUT

thereby set the switching frequency.

(Pin 4): Off-Time Voltage Input. Voltage trip point

V

OFF

for the on-time comparator. Tying this pin to an external
resistive divider from the input makes the off-time pro­portional to V
the pin is grounded and defaults to 2.4V when the pin is
connected to INTV

(Pin 5): Sense Voltage Limit Set. The voltage at this

V

RNG

pin sets the nominal sense voltage at maximum output
current and can be set from 0.5V to 2V by a resistive
divider from INTV
to 95mV when this pin is tied to ground, and 215mV when
tied to INTV

PGOOD (Pin 6): Power Good Output. Open-drain logic
output that is pulled to ground when the output voltage
is not between ±10% of the regulation point. The output
voltage must be out of regulation for at least 125μs before
the power good output is pulled to ground.

SYNC (Pin 7): Sync Pin. This pin provides an external
clock input to the phase detector. The phase-locked loop
will force the rising top gate signal to be synchronized
with the rising edge of the clock signal.

(Pin 8): Error Amplifi er Compensation Point and Cur-

I

TH

rent Control Threshold. The current comparator threshold
increases with control voltage. The voltage ranges from
0V to 2.6V with 1.2V corresponding to zero sense voltage
(zero current).

(Pin 9): Feedback Input. Connect VFB through a resistor

V

FB

divider network to V

PLL/LPF (Pin 10): The phase-locked loop’s lowpass fi lter
is tied to this pin. The voltage at this pin defaults to 1.2V
when the IC is not synchronized with an external clock at
the SYNC pin.

. The comparator defaults to 0.7V when

IN

.

CC

. The nominal sense voltage defaults

CC

.

CC

to set the output voltage.

OUT

SS (Pin 11): Soft-Start Input. A capacitor to ground at
this pin sets the ramp rate of the maximum current sense
threshold.

SGND (Pin 12): Signal Ground. All small signal components
should connect to this ground and eventually connect to
PGND at one point.

SHDN (Pin 13): Shutdown Pin. Pulling this pin below 1.5V
will shut down the LTC3813, turn off both of the external
MOSFET switches and reduce the quiescent supply cur­rent to 240μA.

UVIN (Pin 14): UVLO Input. This pin is input to the internal
UVLO and is compared to an internal 0.8V reference. An
external resistor divider is connected to this pin and the
input supply to program the undervoltage lockout voltage.
When UVIN is less than 0.8V, the LTC3813 is shut down.

NDRV (Pin 15): Drive Output for External Pass Device of
the Linear Regulator for INTV

. Connect to the gate of an

CC

external NMOS pass device and a pull-up resistor to the
input voltage V

EXTV

(Pin 16): External Driver Supply Voltage. When

CC

or the output voltage V

IN

OUT

.

this voltage exceeds 6.7V, an internal switch connects
this pin to INTV

through an LDO and turns off the exter-

CC

nal MOSFET connected to NDRV, so that controller and
gate drive are drawn from EXTV

INTV

(Pin 17): Main Supply Pin. All internal circuits

CC

CC

.

except the output drivers are powered from this pin.
INTV

should be bypassed to ground (Pin 10) with at

CC

least a 0.1μF capacitor in close proximity to the
LTC3813.

(Pin 18): Driver Supply Pin. DRVCC supplies power

DRV

CC

to the BG output driver. This pin is normally connected to
INTV

. DRVCC should be bypassed to BGRTN (Pin 20)

CC

with a low ESR (X5R or better) 1μF capacitor in close
proximity to the LTC3813.

8

3813fa

PIN FUNCTIONS

LTC3813

BG (Pin 19): Bottom Gate Drive. The BG pin drives the
gate of the bottom N-channel main switch MOSFET. This
pin swings from BGRTN to DRV

BGRTN (Pin 20): Bottom Gate Return. This pin connects to
the source of the pulldown MOSFET in the BG driver and
is normally connected to ground. Connecting a negative
supply to this pin allows the main MOSFET’s gate to be
pulled below ground to help prevent false turn-on during
high dV/dt transitions on the SW node. See the Applica­tions Information section for more details.

+

SENSE

parator Input. The (+) input to the current comparator is
normally connected to SW unless using a sense resistor.
The (–) input is used to accurately kelvin sense the bottom
side of the sense resistor or MOSFET.

, SENSE– (Pin 25, Pin 21): Current Sense Com-

CC

.

SW (Pin 26): Switch Node Connection to Inductor and
Bootstrap Capacitor. Voltage swing at this pin is from a
Schottky diode (external) voltage drop below ground
to V

TG (Pin 27): Top Gate Drive. The TG pin drives the gate of
the top N-channel synchronous switch MOSFET. The TG
driver draws power from the BOOST pin and returns to the
SW pin, providing true fl oating drive to the top MOSFET.

BOOST (Pin 28): Top Gate Driver Supply. The BOOST pin
supplies power to the fl oating TG driver. BOOST should
be bypassed to SW with a low ESR (X5R or better) 0.1μF
capacitor. An additional fast recovery Schottky diode from
DRV
charge-pumped supply at BOOST.

.

OUT

to the BOOST pin will create a complete fl oating

CC

3813fa

9

LTC3813

FUNCTIONAL DIAGRAM

V

IN

R

UVIN

UV1

14

R

UV2

SYNC

7

R

C

C

PLL-SYNC

t

= (76pF)

OFF

1.4V

0.7V

C1

V

VOFF

I

IOFF

I

CMP

PLL/LPF

10

V

OFF

4

I

OFF

R

OFF

V

OUT

1

V

RNG

5

I

TH

8

C

C2

0.8V

–

+

20k

+

–

×

2.6V

EA

+

VINUV

R

SQ

–

5V

REG

FAULT

0.8V
REF

1.4μA

Σ

+

INTV

CC

UV

OVERTEMP

SENSE

RUN

SHDN

+

–

1.5V

4V

V

IN

10V

+

NDRV

15

M3

–

OFF

–

6.2V

+

ON

+

–

+

–

ON

SWITCH

LOGIC

SHDN

OV

10V

6.7V

INTV

17

EXTV

16

BOOST

28

TG

27

SW

26

SENSE

25

DRV

18

BG

19

BGRTN

20

SENSE

21

PGOOD

6

CC

CC

+

V

D

B

+

CC

–

IN

+

C

IN

M2

L

V

M1

+

OUT

C

OUT

R2

C

B

C

VCC

–

0.72V

+

UV

13

SHDN

–

+

OV

–

0.85V

V

FB

9

SGND

12

R1

10

0.8V
SS

11

3813 FD

3813fa