LINEAR TECHNOLOGY LTC3802 Technical data

Programmable Up/Down Tracking

FEATURES

■

Wide VIN Range: 3V to 30V Operation with Line
Feedforward Compensation

■

Leading Edge Modulation Architecture for
Extremely Low Duty Cycle Operation

■

Phase-Lockable Fixed Frequency: 330kHz to 750kHz

■

Two 180° Out-of-Phase Controllers

■

Fast Programmable Power-Up/-Down Tracking

■

Programmable Current Limit Without External
Current Sense Resistor

■

Optional Burst Mode® Operation at Light Load

■

±1% 0.6V Voltage Reference

■

External N-Channel MOSFET Architecture

■

Low Shutdown Current: <100µA

■

Overvoltage Protection and PGOOD Flag

■

Small 28-Lead SSOP and 32-Lead QFN Packages

U

APPLICATIO S

■

Notebook and Palmtop Computers

■

Portable Instruments

■

Battery-Operated Digital Devices

■

DC Power Distribution Systems

LTC3802

Dual 550kHz Synchronous

2-Phase DC/DC Controller with

U

DESCRIPTIO

The LTC®3802 is a dual switching regulator controller
optimized for high efficiency step-down conversion from
input voltages between 3V to 30V. The controller uses a
leading edge modulation scheme to allow extremely low
duty cycle operation. The constant frequency voltage mode
controller allows a phase-lockable frequency between
330kHz and 750kHz. Power loss and noise due to the ESR
of the input capacitors are minimized by operating the two
controller output stages 180° out of phase. The synchro­nous buck architecture automatically shifts to Burst Mode
operation as the output load decreases, ensuring maxi­mum efficiency over a wide range of load currents.

The LTC3802 features an onboard, trimmed 0.6V refer­ence and provides better than 1% regulation at the con­verter outputs. A separate output sense provides real time
overvoltage protection and PGOOD sensing. An FBT pin
programs the power-up/-down tracking between the two
channels to meet various sequencing requirements. A
RUN/SS pin provides soft-start and externally program­mable current limit protection functions.

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

Burst Mode is a registered trademark of Linear Technology Corporation.
U.S. Patent Nos 5481178, 5846544, 6304066, 6580258, 5055767, 6307356

TYPICAL APPLICATIO

V

IN

V

OUT1

3.3V
15A

5V TO 22V

10k

56µF

+

2.21k2.21k

10k

25V
×2

4.7µF
25V
×8

+

1500pF

1µH

B340B

330µF
4V
×3

560pF

390Ω

U

CMDSH-3

Si7860DP
×2

Si7440DP
×2

15k

330pF

5V

0.1µF

2200pF

TG1

BOOST1
SW1
BG1
PGND

I

MAX1

FBT
CMPIN1
COMP1
FB1
SGND
FCB
RUN/SS

0.1µF

PV

CC

LTC3802

CMDSH-3

TG2

BOOST2

SW2

BG2

PLLIN

PLLLPF

I

MAX2

CMPIN2

V

COMP2

FB2

PHASEMD

V

INFF

PGOOD

10k

5V

+

10µF

0.1µF

47k47k

CC

0.1µF

V

IN

0.47µF

330pF

Si7860DP
×2

Si7440DP
×2

+

10Ω

10µF

1µH

B340B

330µF

4V
×3

5V

390Ω15k

+

560pF

1500pF2200pF

10k

3.16k 3.16k

10k

3802 TA01

V

2.5V
15A

OUT2

3802f

1

LTC3802

WW

W

U

ABSOLUTE AXI U RATI GS

Supply Voltage

VCC, PVCC............................................................. 7V

BOOSTn.............................................................. 37V

BOOSTn – SWn.................................................... 7V

SWn........................................................ –1V to 30V

Input Voltage

V

.................................................................... 30V

INFF

FBn, CMPINn, FBT, PLLIN, FCB,
RUN/SS, PGOOD, PLLLPF, PHASEMD,
EXTREF, I

n

.......................... –0.3V to VCC + 0.3V

MAX

UUW

PACKAGE/ORDER I FOR ATIO

PV

CC

BG1

BOOST1

TG1

SW1
PGND
I

MAX1

FBT

CMPIN1

10

COMP1

11

FB1

12

SGND

13

FCB

14

RUN/SS

28-LEAD PLASTIC SSOP

T

JMAX

TOP VIEW

1
2
3
4
5
6
7
8
9

GN PACKAGE

= 125°C, θJA = 110°C/W

28
27
26
25
24
23
22
21
20
19
18
17
16
15

BG2
BOOST2
TG2
SW2
PLLIN
PLLLPF
I

MAX2

CMPIN2
V

CC

COMP2
FB2
PHASEMD
V

INFF

PGOOD

ORDER PART

NUMBER

LTC3802EGN

(Note 1)

PGND
PGND

I

MAX1

FBT

CMPIN1

COMP1

FB1

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

LTC3802EGN ................................... –65°C to 150°C

LTC3802EUH ................................... –65°C to 125°C

Lead Temperature (Soldering, 10 sec)

LTC3802EGN Only........................................... 300°C

TOP VIEW

ORDER PART

NUMBER

TG1

BOOST1

BG1

PVCCBG2

BOOST2

TG2

32 31 30 29 28 27 26 25
1SW1
2
3
4
5
6
7
8

9 10 11 12

SGND

32-LEAD (5mm × 5mm) PLASTIC QFN

T

JMAX

EXPOSED PAD (PIN 33) IS GND

MUST BE SOLDERED TO PCB

33

13 14 15 16

FCB

PGOOD

EXTREF

RUN/SS

UH PACKAGE

= 125°C, θJA = 34°C/W

V

INFF

PHASEMD

SW2

FB2

24
23
22
21
20
19
18
17

PGND
PGND
PLLIN
PLLLPF
I

MAX2

CMPIN2
V

CC

COMP2

LTC3802EUH

UH PART

MARKING

3802

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

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range. (Note 3) VCC = PVCC = BOOST = 5V, unless otherwise specified.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V
PV
BV
V

I

VCC

CC

CC

CC

UVLO

VCC Supply Voltage ● 356 V
PVCC Supply Voltage (Note 4) ● 56 V
BOOST Pin Voltage V
Positive Undervoltage Lockout Measured at V

VCC Supply Current VFB = V

– VSW (Note 4) ● 56 V

BOOST

Measured at V

V

RUN/SS

CC
INFF

COMP

= 0V, PLLIN Floating ● 100 150 µA

2.2 2.5 2.8 V

2.2 2.5 2.8 V

● 6.5 9 mA

3802f

2

LTC3802

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range. (Note 3) VCC = PVCC = BOOST = 5V, unless otherwise specified.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

PVCC

I

BOOST

Switcher Control Loop

V

FB

∆V

FB

∆V

OUT

A

ERR

GBW Error AMP Gain Bandwidth Product f = 100kHz (Note 7) 10 MHz
I

COMP

I

FB

I

CMPIN

I

FBT

I

EXTREF

V

EXTREF

A

LFF

R

VINFF

V

PGOOD

V

OVP

V

BURRS

V

SAW

I

IMAX

I

LIM(TH)

I

SS

V

SHDN

LOGIC and PGOOD

I

PHASEMD

V

IH

V

IL

I

PGOOD

V

OLPG

t

PGOOD

PVCC Supply Current VFB = V

V

RUN/SS

BOOST Pin Current VFB = V

V

RUN/SS

Feedback Voltage V

EXTREF

V

EXTREF

= 0V, No Load 2 mA

CMPIN

= 0V (Notes 5, 6) 1 10 µA

= 0V, No Load 1 mA

CMPIN

= 0V (Notes 5, 6) 1 10 µA

= 5V, 0°C ≤ T ≤ 70°C 0.594 0.600 0.606 V
= 5V ● 0.591 0.600 0.609 V

Feedback Voltage VCC Line Regulation VCC = 4.5V to 6V ±0.01 %/V
Output Voltage Load Regulation (Note 7) 0.1 ±0.2 %
Error AMP DC Gain No Load, V

Error AMP Output Sink/Source Current V

RUN/SS

= V

EXTREF

CC

= V

RUN/SS

= V

CC

● 70 80 dB

±12 mA

Voltage Feedback Input Current VFB = 0V to 1V ● ±1 µA
Comparators Input Current V
FBT Input Current V
EXTREF Input Current V
External Reference Not to Affect V
∆ Drop in Duty Cycle/∆ V
V

Input Resistance 1MΩ

INFF

FB

INFF

= 0V to 1V ● ±1 µA

CMPIN

= 0V to 1V ● ±1 µA

FBT

= 0V to 5V ● ±1 µA

EXTREF

● 1V

V

= 5V to 30V 2.3 %/V

VINFF

Positive Power Good Threshold With Respect to 0.6V ● 5 10 15 %
Negative Power Good Threshold With Respect to 0.6V

Overvoltage Threshold With Respect to V
(V

– VFB) to Reset 15 mV

CMPIN

FB

● –5 –10 –15 %

359 %

Burst Mode Operation –12 mV
SAW Before Line Compensation 1.2 V
I

Source Current V

MAX

I

Comparator Offset ● –15 0 15 mV

LIM

V
Hard I

Threshold 5V/V

IMAX/ILIM

Threshold V

LIM/ILIM

RUN/SS Source Current V
RUN/SS Sink/Source Current Ratio V
RUN/SS Sink Current, I
RUN/SS Sink Current, Hard I

LIM

LIM

= 1V –9.0 –10 –11.0 µA

IMAX

= 0V 1.5 V/V

CMPIN

= V

CMPIN
CMPIN

V

CMPIN

V

CMPIN

= 0.6V, V

FBT

= V

= 0.6V, V

FBT

= V

= 0.6V 100 µA

FBT

= V

= 0V ● 1mA

FBT

= V

PHASEMD
PHASEMD

CC

= 0V 1.5 2 2.5 µA/µA

● –8.5 –10 –11.5 µA

–5 –7 –9 µA

RUN/SS Shutdown Threshold RUN/SS↑ ● 0.4 0.8 1.2 V

PHASEMD Pull-Up Current V
PHASEMD Pull-Down Current V

= 0V –7 µA

PHASEMD

= 5V 2 µA

PHASEMD

PLLIN, FCB High Level Input Voltage ● 2.4 V
PLLIN, FCB Low Level Input Voltage ● 0.8 V
V

Leakage Current Power Good ±1 µA

PGOOD

V

Output Low Voltage I

PGOOD

V

Falling Edge Delay (Note 8) ● 100 150 µs

PGOOD

V

Rising Edge Delay (Note 8) 10 µs

PGOOD

= 1mA ● 0.1 0.3 V

PGOOD

3802f

3

LTC3802

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range. (Note 3) VCC = PVCC = BOOST = 5V, unless otherwise specified.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Switcher Switching Characteristics

f

OSC

R

PLLIN

I

PLLLPF

Phase TG1↓ vs PLLIN↓ PHASEMD Floats 0 Deg

V

PHASEMD

DC

MIN

DC

MAX

t

ON(MIN)

t

NOV

R

DS(ON)

Oscillator Frequency PLLIN Open or V

V

= 1.2V 550 kHz

PLLLPF

V

= 0V 250 330 400 kHz

PLLLPF

V

= 2.4V 650 750 850 kHz

PLLLPF

= 0V 490 550 610 kHz

PLLIN

PLLIN Pull-Down Current Source 5 µA
Phase Detector Output Current

Sourcing Capability f
Sinking Capability f

TG1↓ vs PLLIN↓ V

> f

PLLIN

< f

PLLIN

PHASEMD

OSC
OSC

–15 µA
15 µA

= 5V 90 Deg

TG2↓ vs PLLIN↓ PHASEMD Floats 180 Deg
TG2↓ vs PLLIN↓ V

= 5V 270 Deg

PHASEMD

Shutdown Threshold ● 1.2 1.7 V
Floating 2.0 V
90° Phase Threshold ● 3.5 4.0 4.5 V

Minimum TG Duty Cycle V
Maximum TG Duty Cycle V

= 0V ● 0%

PLLIN

PLLIN

= 0V, V

= 0.6V (Note 9) ● 86 89 92 %

CMPIN

TG Minimum Pulse Width (Notes 7, 10) 50 ns
BG Minimum Pulse Width V

= 0V (Note 9) 400 ns

CMPIN

Driver Nonoverlap No Load 10 30 80 ns
TG High R

TG Low R
BG High R
BG Low R

DS(ON)

DS(ON)

DS(ON)

DS(ON)

I

= 100mA (Note 7) 1.6 2.20 Ω

OUT

1.3 1.80 Ω

1.8 2.50 Ω

0.7 1.00 Ω

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

Note 2: The LTC3802 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: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.

Note 4: To ensure proper operation, PV
be greater than V

of the external MOSFETs.

GS(ON)

and BVCC (V

CC

BOOST

– VSW) must

Note 5: Supply current in normal operation is dominated by the current
needed to charge and discharge the external MOSFET gates. This current
will vary with supply voltage and the external MOSFETs used.

Note 6: Supply current in shutdown is dominated by external MOSFET
leakage and may be significantly higher than the quiescent current drawn
by the LTC3802, especially at elevated temperature.

Note 7: Guaranteed by design, not subject to test.
Note 8: Rise and fall times are measured using 10% and 90% levels. Delay

and nonoverlap times are measured using 50% levels.
Note 9: If V

is less than 90% of its nominal value, BG minimum

CMPIN

pulse width is limited to 400ns.
Note 10: The LTC3802 leading edge modulation architecture does not

have a minimum TG pulse width requirement. The TG minimum pulse
width is limited by the rise and fall times.

3802f

4

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC3802

Efficiency vs I

100

EFFICIENCY (%)

Burst Mode

95

OPERATION

90
85
80
75
70
65
60
55
50
45
40

0.1

OUT

CONTINUOUS
MODE

VIN = 12V
V

= 3.3V

OUT

T

= 25°C

A

CIRCUIT ON THE FIRST PAGE
OF THIS DATA SHEET

1 10 100

I

(A)

OUT

Line Regulation

2.5125
VCC = 5V

= 5A

I

OUT

= 25°C

T

2.5075

2.5025

(V)

OUT

V

2.4975

2.4925

2.4875

A

0

10 15 20

5

3802 G01

VIN (V)

Efficiency vs V

100

TA = 25°C

98

CIRCUIT ON THE FIRST PAGE
OF THIS DATA SHEET

96
94
92

V

= 2.5V

0

25 30

3802 G04

OUT

I

OUT

5

0.5

0.4

0.3

0.2

0.1
0
–0.1
–0.2
–0.3
–0.4

–0.5

= 10A

∆V

OUT

(%)

90
88

EFFICIENCY (%)

86
84
82
80

IN

V

= 2.5V

OUT

I

= 5A

OUT

15 20

10

VIN (V)

30

25

3802 G02

Load Regulation

2.5125
VIN = 12V

= 25°C

T

A

CIRCUIT ON THE FIRST PAGE

2.5075
OF THIS DATA SHEET

2.5025

(V)

OUT

V

2.4975

2.4925

2.4875

0

0.5

0.4

0.3

0.2

∆V

0.1

OUT

0

(%)

–0.1
–0.2
–0.3
–0.4

3802 G03

–0.5

20

I

OUT

10

15

(A)

5

VFB vs Temperature

100

125

1.0

0.8

0.6

0.4

0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0

∆V

FB

(%)

606.0

604.8

603.6

602.4

601.2

600.0

(mV)

FB

V

598.8

597.6

596.4

595.2

594.0

VCC = 5V

–50

0

–25

TEMPERATURE (°C)

50

25

75

LTC1323 • TPC05

VFB vs VCC Supply Voltage Line Feedforward Transient

3802 G06

0.5

0.4

0.3

0.2

∆V

0.1

FB

(%)

0
–0.1
–0.2
–0.3
–0.4
–0.5

6

V

OUT

2.5V

(NO LOAD)

AC 50mV/DIV

V

COMP

AC 50mV/DIV

V

5V TO 15V

STEP

5V/DIV

IN

: 1µF/50V ×6

C

IN

SANYO 35CV220AX

10µs/DIV

603.0

602.4

601.8

601.2

600.6

600.0

(mV)

FB

V

599.4

598.8

598.2

597.6

597.0

TA = 25°C

3

4.5

4

3.5
VCC SUPPLY VOLTAGE (V)

5

5.5

3802 G07

3802f

5

LTC3802

TEMPERATURE (°C)

–50 –25

–10

I

LIM(TH)

OFFSET (mV)

–2

10

0

50

75

3802 G13

–6

6

2

25

100

125

VCC = 5V
V

IMAX

= 500mV

UW

TYPICAL PERFOR A CE CHARACTERISTICS

V

OUT

1.2V

50mV/DIV

Load Step in Continuous Mode

50mV/DIV

Load Step in Burst Mode Operation

V

OUT

1.2V

V

SW

10V/DIV

V

OUT

1.2V

50mV/DIV

V

SW

10V/DIV

Burst Mode Waveform
with 0.2A Load

I

OUT

1A TO 10A

STEP

5A/DIV

V

OUT

1.2V

50mV/DIV

V

10V/DIV

INDUCTOR

CURRENT

5A/DIV

10V/DIV

= 12V

IN

CIRCUIT ON
FIRST PAGE OF THIS DATA SHEET

20µs/DIVV

Burst Mode Waveform
with 3A Load

SW

= 12V

IN

CIRCUIT ON
FIRST PAGE OF THIS DATA SHEET

20µs/DIVV

Short-Circuit Test

TG

3802 G08

3802 G11

I

OUT

1A TO 10A

STEP

5A/DIV

10

OFFSET (mV)

LIM(TH)

I

–6

–10

600

580

= 12V

IN

CIRCUIT ON
FIRST PAGE OF THIS DATA SHEET

I

LIM(TH)

TA = 25°C

= 5V

V

CC

6

2

–2

200

0

50µs/DIVV

Offset vs V

400

V

IMAX

Switching Frequency
vs Temperature

VCC = 5V

IMAX

600

(mV)

800

3802 G09

3802 G12

1000

INDUCTOR

CURRENT

5A/DIV

= 12V

IN

CIRCUIT ON
FIRST PAGE OF THIS DATA SHEET

I

LIM(TH)

Switching Frequency
vs VCC Supply Voltage

600

TA = 25°C

580

50µs/DIVV

Offset vs Temperature

3802 G10

RUN/SS

2V/DIV

INDUCTOR

CURRENT

20A/DIV

6

CIRCUIT ON
FIRST PAGE OF THIS DATA SHEET

= 12V, V

V

IN

= 47k, L = 1µH (TOKO-FDA1254-1ROM)

R

I(MAX)

5µs/DIV

= 3.3V, CSS = 0.01µF,

OUT

3802 G14

560

540

520

SWITCHING FREQUENCY (kHz)

500

–50 –25

25

0

TEMPERATURE (°C)

560

540

SWITCHING FREQUENCY (kHz)

520

50

75

100

125

3802 G15

500

3

4 4.5 5

3.5
VCC SUPPLY VOLTAGE (V)

5.5 6

3802 G16

3802f

UW

TEMPERATURE (°C)

–50

MAXIMUM DUTY CYCLE (%)

95

25

3802 G19

80

70

–25 0 50

65

60

100

90

85

75

75 100 125

VCC = 5V
f

SW

= 550kHz

V

CMPIN

> 0.54V

V

CMPIN

< 0.54V

TYPICAL PERFOR A CE CHARACTERISTICS

Switching Frequency vs V

850

TA = 25°C

= 5V

V

CC

750

PLLLPF

AC 20mV/DIV

Continuous Mode Operation

V

OUT1

5V

LTC3802

Maximum Duty Cycle
vs Temperature

650

550

450

SWITCHING FREQUENCY (kHz)

350

250

0

0.8 1.2 1.6

0.4
V

PLLLPF

Maximum Duty Cycle
vs VCC Supply Voltage

100

TA = 25°C

= 550kHz

f

SW

95

90

85

80

75

70

MAXIMUM DUTY CYCLE (%)

65

0

3

V

CMPIN

V

< 0.54V

CMPIN

3.5 4 5
VCC SUPPLY VOLTAGE (V)

(V)

> 0.54V

4.5

2 2.4

3802 G17

5.5

3802 G20

6

TG1

20V/DIV

V

OUT2

TG2

20V/DIV

1V

= 30V

IN

AC 20mV/DIV

Maximum Duty Cycle
vs Switching Frequency Duty Cycle vs V

100

TA = 25°C

= 5V

V

CC

95

90

85

80

75

70

MAXIMUM DUTY CYCLE (%)

65

60

390 450 570

330

0.5µs/DIVV

V

> 0.54V

CMPIN

V

< 0.54V

CMPIN

510

SWITCHING FREQUENCY (kHz)

630 690 750

3802 G18

3802 G21

100

90

VIN = 5V

80

VIN = 12V

70
60
50
40

DUTY CYCLE (%)

30
20
10

0

0.8

1 1.4

1.2
V

COMP

1.6

COMP

(V)

1.8

VIN = 30V

VIN = 20V

TA = 25°C

= 5V

V

CC

V

CMPIN

2

= V

2.2

FB

2.4

3802 G22

I

IMAX

vs Temperature

12.0
VCC = 5V

11.5

11.0

10.5

(µA)

10.0

IMAX

I

9.5

9.0

8.5

8.0
–50

–25 0 50

and I

RUN/SS

TEMPERATURE (°C)

I

RUN/SS

SINK CURRENT

I

IMAX

I

RUN/SS

SOURCE CURRENT

25

75 100 125

3802 G23

20

15

10

5

0

–5

–10

–15

–20

I

RUN/SS

(µA)

(µA)

IMAX

I

11.5

10.9

10.3

9.7

9.1

8.5

I

vs VCC Supply Voltage

IMAX

TA = 25°C

3

4 4.5 5

3.5
VCC SUPPLY VOLTAGE (V)

5.5 6

3802 G24

Driver Supply Current vs Load

80

TA = 25°C

= V

PV

CC

60

40

20

DRIVER SUPPLY CURRENT (mA)

0

0

– VSW = 5V

BOOST

2000

4000

CTG, CBG LOAD (pF)

6000

I

PVCC

I

BOOST1

I

BOOST2

8000

10000

3802 G25

3802f

7

LTC3802

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Supply Current vs Temperature Supply Current vs Supply Voltage

10

I

VCC

1

I

PVCC

(NO LOAD)

I

BOOST1

I

BOOST2

(NO LOAD)

10

1

TA = 25°C

I

PVCC

(NO LOAD)

I

VCC

I

BOOST1, IBOOST2

(NO LOAD)

0.1

SUPPLY CURRENT (mA)

0.01

VCC = V

–50 –25

= V

PVCC

0 25 50 75 100 125

TEMPERATURE (°C)

BOOST

I

SHUTDOWN

– VSW = 5V

VCC

3802 G26

UUU

PI FU CTIO S

PVCC (Pin 1/Pin 29): Driver Power Supply Input. PV
provides power to the two BG drivers and must be con­nected to an external voltage high enough to fully turn on
the external MOSFETs, QB1 and QB2. PVCC requires at
least a 10µF bypass capacitor directly to PGND.

BG1 (Pin 2/Pin 30): Channel 1 Controller Bottom Gate
Drive. The BG1 pin drives the gate of the bottom N-channel
synchronous switch MOSFET, QB1. BG1 is designed to
drive typically up to 10,000pF of gate capacitance.

BOOST1 (Pin 3/Pin 31): Channel 1 Controller Top Gate
Driver Supply. BOOST1 should be bootstrapped to SW1
with a 0.1µF capacitor. An external Schottky diode from
PVCC to BOOST1 creates a complete floating charge­pumped supply at BOOST1. No other external supplies are
required.

TG1 (Pin 4/Pin 32): Channel 1 Controller Top Gate Drive.
The TG1 pin drives the top N-channel MOSFET with a
voltage swing equal to PVCC superimposed on the switch
node voltage SW1. TG1 is designed to drive typically up to
6000pF of gate capacitance.

(28-Pin SSOP/32-Pin QFN Package)

CC

0.1

SUPPLY CURRENT (mA)

0.01
3

I

SHUTDOWN

VCC

453.5 4.5 5.5 6

SUPPLY VOLTAGE (V)

3802 G27

SW1 (Pin 5/Pin 1): Channel 1 Controller Switching Node.
Connect SW1 to the switching node of the channel 1
converter. When the bottom MOSFET QB1 turns on, the
current limit comparator and the burst comparator
monitor the voltage at SW1. If the voltage drop across
MOSFET QB1 is too large, the controller enters current
limit; if it is too small, the switcher enters Burst Mode
operation. See Current Limit and Burst Mode Applica­tions Information.

PGND (Pin 6/Pins 2, 3, 23, 24): Power Ground. The BG
drivers return to this pin. Connect PGND to a high current
ground node in close proximity to the sources of external
MOSFETs QB1 and QB2 and the VIN, PVCC and V

OUT

bypass capacitors.

I

(Pin 7/Pin 4): Channel 1 Controller Current Limit

MAX1

Set. The I

pin has an internal 10µA current source

MAX1

pull-up, allowing the current limit and burst comparator
threshold to be programmed by a single external resistor
to SGND. See Current Limit and Burst Mode Applications
Information.

8

3802f

UUU

PI FU CTIO S

LTC3802

(28-Pin SSOP/32-Pin QFN Package)

FBT (Pin 8/Pin 5): Feedback Tracking Input. FBT should be

connected through a resistive divider network to V
set the channel 1 output slew rate. Upon power-up/-down,
the LTC3802 servos FBT and CMPIN2 to the same poten­tial to control the output power-up/-down slew rate. To
program both outputs to have the same slew rate, dupli­cate the CMPIN2 resistive divider at FBT. To have a
ratiometric slew rate, short FBT to CMPIN1. To disable the
tracking function, short FBT to CMPIN2.

CMPIN1 (Pin 9/Pin 6): Channel 1 Controller Comparators
Input. CMPIN1 should be connected through a resistive
divider network to V
voltage. To improve transient response, a feedforward
capacitor can be added to the resistive divider. The power
good comparators, overvoltage comparator and Burst
reset comparators monitor this node directly. CMPIN1 is
a sensitive pin, avoid coupling noise into this pin.

COMP1 (Pin 10/Pin 7): Channel 1 Controller Error Ampli­fier Output. The COMP1 pin is connected directly to the
channel 1 error amplifier output and the input of the line
feedforward circuit. Use an RC network between the
COMP1 pin and the FB1 pin to compensate the feedback
loop for optimum transient response. Under start-up
conditions, the potential at RUN/SS controls the slew rate
at COMP1.

FB1 (Pin 11/Pin 8): Channel 1 Controller Error Amplifier
Input. FB1 should be connected through a resistive divider
network to V
voltage. Also, connect the channel 1 switcher loop com­pensation network to FB1.

SGND (Pin 12/Pin 9): Signal Ground. All the internal low
power circuitry returns to the SGND pin. Connect to a low
impedance ground, separated from the PGND node. All
feedback, compensation and soft-start connections should
return to SGND. SGND and PGND should be connected
only at a single point, near the PGND pin and the negative
terminal of the VIN bypass capacitor.

to set the channel 1 switcher output

OUT1

to monitor its real time output

OUT1

OUT1

to

FCB (Pin 13/Pin 10): Force Continuous Bar. Internally
pulled high. When FCB is shorted to GND, the controller
forces both converters to maintain continuous synchro­nous operation regardless of load current.

EXTREF (Pin 11, QFN Package Only): External Reference.
The EXTREF pin and the internal bandgap voltage are used
as the switcher control loop’s reference in a diode OR
manner. If the potential at the EXTREF pin is less than 0.6V,
it overrides the internal reference and lowers the switcher
output voltages. If EXTREF potential is more than 1V, the
internal bandgap voltage controls both channel output
voltages. EXTREF has no effect on the PGOOD threshold.
EXTREF is internally connected to the RUN/SS pin in the
GN28 package.

RUN/SS (Pin 14/Pin 12): Run Control and Soft-Start
Input. An internal 7µA current source pull-up and an
external capacitor to ground at this pin sets the start-up
delaly (approximately 300ms/µF), the output ramp rate
and the time delay for soft current limit. Forcing this pin
below 0.8V with an open-drain/collector transistor shuts
down the device. Pulling RUN/SS high with a current
greater than 10µA can result in malfunctioning of tracking
during start-up. Pulling RUN/SS high with currents higher
than 50µA can interfere with current limit protection.

PGOOD (Pin 15/Pin 13): Open-Drain Power Good Output.
PGOOD is pulled to ground under shutdown condition or
when any switcher output voltage is not within ±10% of its
set point .

V

(Pin 16/Pin 14): Line Feedforward Compensation

INFF

Input. Connects to the VIN power supply to provide line
feedforward compensation. A change in VIN immediately
modulates the input to the PWM comparator and changes
the pulse width in an inversely proportional manner, thus
bypassing the feedback loop and providing excellent tran­sient line regulation. V
lowpass filter can be added to this pin to prevent noisy
signals from affecting the loop gain.

is a sensitive pin, an external

INFF

3802f

9