SC2441A(2006) Просмотр технического описания (PDF) - Semtech Corporation

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SC2441A
(Rev.:2006)

1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter

Semtech Corporation 

SC2441A

POWER MANAGEMENT

Pin Descriptions

Pin

Pin Name Pin Function

1

IN

Supply Voltage for the Boost Converter. Tie to VCC if boost converter is not used to generate

auxiliary supply.

2

PLLF

Compensation Pin for the Phase Lock Loop.

An external resistor and an external capacitor tied to this pin set the first step-down converter

3

SS1/EN1 soft-start time and its overload hiccup cycle time. Pulling this pin below 0.6V shuts off channel 1

gate drivers.

4

CS1+

The Non-inverting Input to the Channel 1 Current-sense Amplifier/Comparator.

5

CS1-

The Inverting Input to the Channel 1 Current-sense Amplifier/Comparator. Normally tied to the

output of the converter.

Synchronization and Shutdown Input. Tie this pin to IN (Pin 1) or to a voltage above 1.5V to enable

the SC2441A. Pulling this pin below 0.5V shuts off both step-down controllers and the boost

6

SYNC/SHDN regulator. Driving this pin with an external clock synchronizes the SC2441A. The boost converter

runs at twice of the external clock frequency whereas the step-down controllers operate at the

clock frequency.

7

FB3

The Inverting Input to Boost Error Amplifier. FB3 is tied to an external resistive divider for OUT3

voltage setting.

8

COMP3

Boost Converter Error Amplifier Output. Used for loop compensation. Pulling this pin below 0.4V

disables the step-up converter.

9

GND

Analog Ground.

10

ROSC

An external resistor connected from this pin to GND sets the oscillator free-running frequency.

11

FB1

The Inverting Input to the Channel 1 Error Amplifier. Tie to an external resistive divider between

OUT1 and the ground for output voltage sensing.

12

COMP1 Channel 1 Error Amplifier Output. Used for loop compensation.

13

COMP2

14

FB2

15

CS2-

16

CS2+

17

SS2/EN2

18

BST2

19

GDH2

 2006 Semtech Corp.

Channel 2 Error Amplifier Output. Used for loop compensation.

The Inverting Input to the Channel 2 Error Amplifier. Tie to an external resistive divider between

OUT2 and the ground for output voltage sensing. Tie to IN or VCC for two-phase single output

operation.

The Inverting Input to the Channel 2 Current-sense Amplifier/Comparator. Normally tied to the

output of the converter.

The Non-inverting Input to the Channel 1 Current-sense Amplifier/Comparator.

An external resistor and an external capacitor tied to this pin set the second step-down converter

soft-start time and its overload hiccup cycle time. Pulling this pin below 0.6V shuts off channel 2

gate drivers. Leave open for two-phase single output operation.

Bootstrapped Supply for Channel 2 Upper Gate Drive. Connect to a bootstrap capacitor and an

external diode.

Gate Drive Output for Channel 2 Upper MOSFET. Gate drive voltage swings from ground to

VBST2.

6

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