UCC2912

UCC3912

PROGRAMMABLE HOT SWAP POWER MANAGER

SLUS241D − MARCH 1994 - REVISED NOVEMBER 2003

4

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electrical characteristics, these specifications apply for TA = −40°C to 85°C for the UCC2912;

TA = 0°C to 70°C for the UCC3912, VIN = 5 V, IMAX = 0.4 V, SHTDWN = 2.4 V

(unless otherwise stated)

timer section

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNITS

CT charge current

VCT = 1.0 V

−45.0

-36.0

−22.0

µA

CT discharge current

UCC2912

VCT = 1.0 V

0.72

1.20

1.57

µA

CT discharge current

UCC3912

VCT = 1.0 V

0.72

1.20

1.50

µA

Output duty cycle

VOUT = 0 V

2.0

3.0

6.0

%

CT fault threshold

1.3

1.5

1.7

V

CT reset threshold

0.4

0.5

0.6

V

NOTE 1: All voltages are with respect to ground. Current is positive into and negative out of the specified terminal.

shutdown section

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNITS

Shutdown threshold

1.1

1.5

1.9

V

Shutdown hysteresis

100

mV

Input current

SHTDWN = 1 V

100

500

nA

fault output section

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNITS

Output leakage current

500

nA

Low level output voltage

IOUT = 10 mA

0.4

0.8

V

TTL input dc characteristics section

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNITS

TTL input voltage high

(can be connected to VIN)

2.0

V

TTL input voltage low

0.8

V

TTL input high current

VIH = 2.4 V

3

10

µA

TTL input low current

VIL = 0.4 V

1

µA

NOTE 1: All voltages are with respect to ground. Current is positive into and negative out of the specified terminal.

pin description

B0−B3: These pins provide digital input to the DAC which sets the fault current threshold. They can be used

to provide a digital soft-start, adaptive current limiting.

CT: A capacitor connected to ground sets the maximum fault time. The maximum fault time must be more than

the time to charge the external capacitance in one cycle. The maximum fault time is defined as

FAULT = 27.8

× 103 × CT. Once the fault time is reached the output will shutdown for a time given by:

TSD = 833 × 103 × CT, this equates to a 3% duty cycle.

FAULT: Open drain output which pulls low upon any condition which causes the output to open: fault, thermal

shutdown, or shutdown.

IMAX: When this pin is set to logic low the maximum sourcing current will always be 1 A above the programmed

fault level. When set to logic high, the maximum sourcing current will be a constant 4 A for applications which

require fast charging of load capacitance.