Linear Technology LTC1430 Datasheet

FEATURES

LTC1430

High Power Step-Down

Switching Regulator Controller

U

DESCRIPTIO

■

High Power 5V to 3.xV Switching Controller:
Can Exceed 10A Output

■

All N-Channel External MOSFETs

■

Constant Frequency Operation—Small Inductor

■

Excellent Output Regulation: ±1% Over Line, Load
and Temperature Variations

■

High Efficiency: Over 95% Possible

■

Fixed Frequency Operation

■

No Low Value Sense Resistor Needed

■

Outputs Can Drive External FETs with Up to
10,000pF Gate Capacitance

■

Quiescent Current: 350µA Typ, 1µA in Shutdown

■

Fast Transient Response

■

Adjustable or Fixed 3.3V Output

■

Available in 8- and 16-Lead PDIP and SO Packages

U

APPLICATIO S

■

Power Supply for P6 and Pentium
Microprocessors

■

High Power 5V to 3.xV Regulators

■

Local Regulation for Dual Voltage Logic Boards

■

Low Voltage, High Current Battery Regulation

®

The LTC®1430 is a high power, high efficiency switching
regulator controller optimized for 5V to 3.xV applications.
It includes a precision internal reference and an internal
feedback system that can provide output regulation of ±1%
over temperature, load current and line voltage shifts. The
LTC1430 uses a synchronous switching architecture with
two N-channel output devices, eliminating the need for a
high power, high cost P-channel device. Additionally, it
senses output current across the drain-source resistance
of the upper N-channel FET, providing an adjustable
current limit without an external low value sense resistor.

The LTC1430 includes a fixed frequency PWM oscillator for
low output ripple under virtually all operating conditions.
The 200kHz free-running clock frequency can be externally
adjusted from 100kHz to above 500kHz. The LTC1430
features low 350µA quiescent current, allowing greater
than 90% efficiency operation in converter designs from
1A to greater than 50A output current. Shutdown mode
drops the LTC1430 supply current to 1µA.

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

Pentium is a registered trademark of Intel Corporation.

TYPICAL APPLICATIO

Typical 5V to 3.3V, 10A Application

VIN 5V

+

R

C

7.5k
C

4700pF

1µF

0.01µF

C

PV

CC2

V

CC

SS

LTC1430

FREQSET
SHDN
COMP

SENSE

PV

CC1

I

MAX

PGND

GND

SENSE

–

4.7µF

100Ω

+

0.1µF

SHUTDOWN

C1
220pF

U

1N4148

G1

I

FB

G2NC

+

FB NC

16k

0.1µF

0.1µF

1k

: AVX-TPSE227M010R0100

C

IN

C

: AVX-TPSE337M006R0100

OUT

L1: ETQP6F1R6SFA
M1A, M1B, M2: MOTOROLA MTD20N03HL

+

C

IN

220µF
×4

M1A, M1B
2 IN PARALLEL

L1, 2.8µH

+

M2

C

OUT

330µF
×6

LTC1430 • TA01

3.3V
10A

100

TA = 25°C
V

= 5V

IN

90

= 3.3V

V

OUT

80

70

EFFICIENCY (%)

60

50

40

0.1 1

Efficiency

10

LOAD CURRENT (A)

LTC1430 • TA02

1

LTC1430

WW

W

U

ABSOLUTE AXI U RATI GS

Supply Voltage

VCC....................................................................... 9V

PV

.............................................................. 13V

CC1, 2

Input Voltage

IFB......................................................... –0.3V to 18V

All Other Inputs ...................... –0.3V to (VCC + 0.3V)

UUW

PACKAGE/ORDER I FOR ATIO

ORDER

TOP VIEW

G1

1

PV

2

CC1

GND

3

FB

4

N8 PACKAGE
8-LEAD PDIP

T

= 150°C, θJA = 100°C/W (N8)

JMAX

= 150°C, θJA = 150°C/W (S8)

T

JMAX

G2

8

V

/PV

7

CC

COMP

6

SHDN

5

S8 PACKAGE

8-LEAD PLASTIC SO

CC2

PART NUMBER

LTC1430CN8
LTC1430CS8

S8 PART MARKING

1430

(Note 1)

Operating Temperature Range

LTC1430C .............................................. 0°C to 70°C

LTC1430I........................................... –40°C to 85°C

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

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

TOP VIEW

G1

PV

CC1

PGND

GND

–

SENSE

FB

+

SENSE

SHDN

N PACKAGE

16-LEAD PDIP

T

JMAX

T

JMAX

1
2
3
4
5
6
7
8

16-LEAD PLASTIC SO

= 150°C, θJA = 70°C/W (N)

= 150°C, θJA = 110°C/W (S)

G2

16

PV

15

V

14

CC

I

13

FB

I

12

MAX

FREQSET

11

COMP

10

SS

9

S PACKAGE

PART NUMBER

CC2

LTC1430CN
LTC1430CS

LTC1430IS

ORDER

Consult factory for Industrial and Military grade parts.

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise noted. (Note 2)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V
PV
V
V

∆V

IV

IPV

f

OSC

CC

CC

OUT

FB

OUT

CC

CC

Supply Voltage ● 48V
PV

CC1

, PV

CC2

● 13 V

Output Voltage Figure 1 ● 3.30 V
Feedback Voltage Figure 1, SENSE+ and SENSE– Floating (LTC1430C) ● 1.25 1.265 1.28 V

Figure 1, SENSE

Output Load Regulation Figure 1, I

Figure 1, I

+

and SENSE– Floating (LTC1430I) ● 1.23 1.265 1.29 V

= 0A to 10A (Note 3) (LTC1430C) ● 520 mV

OUT

= 0A to 10A (Note 3) (LTC1430I) 5 mV

OUT

Output Line Regulation Figure 1, VCC = 4.75V to 5.25V (Note 3) (LTC1430C) ● 15 mV

Figure 1, V

Supply Current (VCC Only) Figure 2, V

V

SHDN

Supply Current (PVCC) Figure 2, PVCC = 5V, V

V

SHDN

= 4.75V to 5.25V (Note 3) (LTC1430I) 1 mV

CC

SHDN

= V

CC

● 350 700 µA

= 0V 1 10 µA

= VCC (Note 4) 1.5 mA

SHDN

= 0V 0.1 µA

Internal Oscillator Frequency FREQSET Floating (LTC1430C) ● 140 200 260 kHz

FREQSET Floating (LTC1430I)

● 130 200 300 kHz

2

LTC1430

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise noted. (Note 2)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

IH

V

IL

I

IN

A

V

gm

V

gm

I

I

MAX

I

SS

tr, t

s

t

NOV

DC

MAX

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

Note 2: 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 3: This parameter is guaranteed by correlation and is not tested
directly.

SHDN Input High Voltage ● 2.4 V
SHDN Input Low Voltage ● 0.8 V
SHDN Input Current ● ±0.1 ±1 µA
Error Amplifier Open-Loop DC Gain (LTC1430I) ● 40 48 dB
Error Amplifier Transconductance (LTC1430C) 650 µMho

(LTC1430I)

I

Amplifier Transconductance (Note 5) 1300 µMho

LIM

I

Sink Current V

MAX

= VCC (LTC1430C) ● 81216 µA

I(MAX)

= VCC (LTC1430I) ● 81217 µA

V

I(MAX)

● 300 650 1200 µMho

Soft-Start Source Current VSS = 0 (LTC1430C) ● –8 –12 –16 µA

V

= 0 (LTC1430I) ● –8 –12 –17 µA

SS

Driver Rise/Fall Time Figure 3, PV
Driver Non-Overlap Time Figure 3, PV
Maximum Duty Cycle V

= VCC (LTC1430C) ● 90 96 %

COMP

V

= VCC, VFB = 0 (LTC1430I) ● 90 96 %

COMP

V

= VCC, VFB = 1.265V (LTC1430I) ● 83 88 %

COMP

CC1

CC1

= PV

= 5V 80 250 ns

CC2

= PV

= 5V 25 130 250 ns

CC2

Note 4: Supply current in normal operation is dominated by the current
needed to charge and discharge the external FET gates. This will vary with
the LTC1430 operating frequency, operating voltage and the external FETs
used.

Note 5: The I
normal (not current limited) operation, the I

amplifier can sink but cannot source current. Under

LIM

output current will be zero.

LIM

3

LTC1430

UUU

PI FU CTIO S

(16-Lead Package/8-Lead Package)

G1 (Pin 1/Pin 1): Driver Output 1. Connect this pin to the

gate of the upper N-channel MOSFET, M1. This output will
swing from PV

to PGND. It will always be low when G2

CC1

is high.

PV

(Pin 2/Pin 2): Power VCC for Driver 1. This is the

CC1

power supply input for G1. G1 will swing from PGND to
PV

. PV

CC1

PVCC + V

must be connected to a potential of at least

CC1

(M1). This potential can be generated

GS(ON)

using an external supply or a simple charge pump con­nected to the switching node between the upper MOSFET
and the lower MOSFET; see Applications Information for
details.

PGND (Pin 3/Pin 3): Power Ground. Both drivers return to
this pin. It should be connected to a low impedance ground
in close proximity to the source of M2. 8-lead parts have
PGND and GND tied together at pin 3.

GND (Pin 4/Pin 3): Signal Ground. All low power internal
circuitry returns to this pin. To minimize regulation errors
due to ground currents, GND should be connected to
PGND right at the LTC1430. 8-lead parts have PGND and
GND tied together internally at pin 3.

SENSE–, FB, SENSE+ (Pins 5, 6, 7/Pin 4): These three
pins connect to the internal resistor divider and to the
internal feedback node. To use the internal divider to set
the output voltage to 3.3V, connect SENSE+ to the positive
terminal of the output capacitor and SENSE– to the nega­tive terminal. FB should be left floating in applications that
use the internal divider. To use an external resistor divider
to set the output voltage, float SENSE+ and SENSE– and
connect the external resistor divider to FB.

SHDN (Pin 8/Pin 5): Shutdown. A TTL compatible low
level at SHDN for longer than 50µs puts the LTC1430 into
shutdown mode. In shutdown, G1 and G2 go low, all
internal circuits are disabled and the quiescent current
drops to 10µA max. A TTL compatible high level at SHDN
allows the part to operate normally.

SS (Pin 9/NA): Soft-Start. The SS pin allows an external
capacitor to be connected to implement a soft-start func­tion. An external capacitor from SS to ground controls the
start-up time and also compensates the current limit loop,
allowing the LTC1430 to enter and exit current limit
cleanly. See Applications Information for more details.

COMP (Pin 10/Pin 6): External Compensation. The COMP
pin is connected directly to the output of the error amplifier
and the input of the PWM. An RC network is used at this
node to compensate the feedback loop to provide opti­mum transient response. See Applications Information for
compensation details.

FREQSET (Pin 11/NA): Frequency Set. This pin is used to
set the free running frequency of the internal oscillator.
With the pin floating, the oscillator runs at about 200kHz.
A resistor from FREQSET to ground will speed up the
oscillator; a resistor to VCC will slow it down. See Applica­tions Information for resistor selection details.

I

(Pin 12/NA): Current Limit Set. I

MAX

sets the thresh-

MAX

old for the internal current limit comparator. If IFB drops
below I
limit. I

with G1 on, the LTC1430 will go into current

MAX

has a 12µA pull-down to GND. It can be adjusted

MAX

with an external resistor to PVCC or an external voltage
source.

IFB (Pin 13/NA): Current Limit Sense. Connect to the
switched node at the source of M1 and the drain of M2
through a 1k resistor. The 1k resistor is required to prevent
voltage transients from damaging IFB. This pin can be
taken up to 18V above GND without damage.

VCC (Pin 14/Pin 7): Power Supply. All low power internal
circuits draw their supply from this pin. Connect to a clean
power supply, separate from the main PVCC supply at the
drain of M1. This pin requires a 4.7µF bypass capacitor.
8-lead parts have VCC and PV

tied together at pin 7 and

CC2

require a 10µF bypass to GND.

PV

(Pin 15/Pin 7): Power VCC for Driver 2. This is the

CC2

power supply input for G2. G2 will swing from GND to
PV

. PV

CC2

supply. The 8-lead parts have VCC and PV

is usually connected to the main high power

CC2

tied together

CC2

at pin 7 and require a 10µF bypass to GND.
G2 (Pin 16/Pin 8): Driver Output 2. Connect this pin to the

gate of the lower N-channel MOSFET, M2. This output will
swing from PV

to PGND. It will always be low when G1

CC2

is high.

4

BLOCK DIAGRA

SHDN

W

DELAY

50µs

INTERNAL
SHUTDOWN

LTC1430

FREQSET

COMP

V

CC

SS

I

MAX

TEST CIRCUITS

+

4.7µF

12µA

12µA

100Ω

0.1µF

SHUTDOWN

C1
220pF

+

R

7.5k

C

I

LIM

–

1µF

0.01µF

C

C

4700pF

+

PVCC = 5V

PV

CC2

V

CC

SS

LTC1430

FREQSET
SHDN
COMP

SENSE

FB MIN

+

–

+

1.26V

1N4148

PV

CC1

G1

I

MAX

I

FB

G2NC

PGND

GND

+

SENSE

FB NC

–

PWM

40mV

+

+

C

IN

220µF
×4

M1A, M1B
2 IN PARALLEL

0.1µF

M1A, M1B, M2: MOTOROLA MTD20N03HL

: AVX-TPSE227M010R0100

C

IN

: AVX-TPSE337M006R0100

C

OUT

2.7µH/15A

M2

+

C
330µF
×6

OUT

PV

CC1

G1

PV

CC2

G2

PGND

MAX

I

FB

+

LTC1430 • BD

NC

LTC1430 • F01

FB

SENSE

SENSE

V

OUT

+

–

1.61k

1k

+

40mV

3.3V

20.1k

12.4k

FB MEASUREMENT

LTC1430

SENSE

FB

–

SENSE

NC

Figure 1

V

GND

CC

5V

PV

CC1

LTC1430

PV

CC2

PGND

G1

G2

10µF 0.1µF

10,000pF

10,000pF

Figure 3

G1 RISE/FALL

G2 RISE/FALL

LTC1430 • TC03

PV

LTC1430

SENSE

PV

CC1IFB

CC

G1

NC

G2

NC

FB

NC

+

–

LTC1430 • TC02

V

V

SHDN

CC

SHDN

V

CCPVCC2

I

NC

MAX

FREQSET

NC

COMP

NC

SS

NC

GND PGND SENSE

Figure 2

5