3

Rev. 05/25/04

SP6128A Low Voltage, Synchronous Step Down PWM Controller

© Copyright 2004 Sipex Corporation

PIN DESCRIPTION

PIN N0.

PIN NAME

DESCRIPTION

1GL

High current driver output for the low side MOSFET switch. It is always low if GH is high.

Positive input supply for the logic circuitry. Properly bypass this pin to GND with a low ESL/

ESR ceramic capacitor or RC filter.

4

PGND

Power ground pin.

5

GND

Signal ground pin.

6

COMP

Output of the Error Amplifier. It is internally connected to the inverting input of the PWM

comparator. A lead-lag network is typically connected to the COMP pin to compensate the

feedback loop in order to optimize the dynamic performance of the voltage mode control

loop. Sleep mode can be invoked by pulling the COMP pin below 0.3V with an external

open-drain or open-collector transistor. An internal 5µA pull-up ensures start-up.

7, 8, 9

NC

No connect.

10

Feedback Voltage Pin. It is the inverting input of the Error Amplifier and serves as the

output voltage feedback point for the Buck converter. The output voltage is sensed and

can be adjusted through an external resistor divider.

11

Overcurrent program pin. A resistor programs the overcurrent threshold. The overcurrent

side MOSFET is turned on. This prevents excessive power dissipation in the external

power MOSFETs during an overload condition. An internal delay circuit prevents false

shutdowns that might otherwise occur during very short, mild overload conditions,due to

load transients.

12

SWN

Lower supply rail for the GH high-side gate driver. It also connects to the Current Limit

comparator. Connect this pin to the switching node at the junction between the two

of the high side N-channel MOSFET while it is conducting.

13

GH

High current driver output for the high side MOSFET switch. It is always low if GL is high or

during a fault. GH swings from SWN to BST.

14

BST

High side driver supply pin. Connect BST to the external boost diode and capacitor as

shown in the application schematic on page 1.

ELECTRICAL CHARACTERISTICS

SWN = GND = 0V, typical value for design guideline only.

PARAMETER

MIN

TYP

MAX

UNITS CONDITIONS

SOFT START, SHUTDOWN, UVLO

Internal Soft Start Slew Rate

0.1

0.3

0.6

V/ms

COMP pin, on transition from

shutdown

COMP Discharge Current

183

µA

COMP = 0.5V, Fault Initiated

COMP Clamp Voltage

0.55

0.65

0.75

V

COMP Clamp Current

10

30

65

µA

Shutdown Threshold Voltage

0.29

0.34

0.39

V

Measured at COMP Pin

Shutdown Input Pull-up Current

2

5

10

µA

COMP = 0.2V, Measured at COMP pin

2.63

2.8

2.95

V

2.47

2.7

2.9

V

GATE DRIVERS

GH Rise Time

60

110

ns

GH Fall Time

60

110

ns

GL Rise Time

60

110

ns

GL Fall Time

60

110

ns

GH to GL Non-Overlap Time

0

100

140

ns

GL to GH Non-Overlap Time

0

100

140

ns