UCC1917

UCC2917

UCC3917

SLUS203A - AUGUST 1999

FEATURES

• Manages Hot Swap of 15V and

Above

• Precision Fault Threshold

• Programmable Average Power

Limiting

• Programmable Linear Current

Control

• Programmable Overcurrent Limit

• Programmable Fault Time

• Internal Charge Pump to Control

External NMOS Device

• Fault Output and Catastrophic

Fault Indication

• Fault Mode Programmable to

Latch or Retry

• Shutdown Control

• Undervoltage Lockout

Positive Floating Hot Swap Power Manager

12

11

8

7

6

5

10

4

2

3

1

13

16

9

15

14

5V

VOUT

V

DD

VDD

VOUT

DISABLE

OUTPUT

LOW

ON-TIME

DELAY

V

DD

40

µA

VOUT

UVLO

>10V=ENABLE

< 6V=DISABLE

5V

REFERENCE

LOGIC

SUPPLY

SHTDWN

FLTOUT

C1P

C1N

C2P

C2N

VSS

VREF/CATFLT

MAXI

CT

VOUT

SENSE

OUTPUT

PLIM

LATCH

VDD

200mV

OVER

CURRENT

COMPARATOR

40

µA

50mV

4V

BLOCK DIAGRAM

UDG-99055

DESCRIPTION

The UCC3917 family of positive floating hot swap managers provides complete

power management, hot swap, and fault handling capability. The voltage limita-

tion of the application is only restricted by the external component voltage limi-

tations. The IC provides its own supply voltage via a charge pump off of VOUT.

The onboard 10V shunt regulator protects the IC from excess voltage. The IC

also has catastrophic fault indication to alert the user that the ability to shut off

the output NMOS has been bypassed. All control and housekeeping functions

are integrated and externally programmable. These include the fault current

level, maximum output sourcing current, maximum fault time, soft start time,

and average NMOS power limiting.

The fault level across the current sense amplifier is fixed at 50mV to minimize

total drop out. Once 50mV is exceeded across the current sense resistor, the

fault timer will start. The maximum allowable sourcing current is programmed

with a voltage divider from the VREF/CATFLT pin to generate a fixed voltage

on the MAXI pin. The current level at which the output appears as a current

trolled current startup can be programmed with a capacitor on MAXI.

When the output current is below the fault level, the output device is switched

on with full gate drive. When the output current exceeds the fault level, but is

less than maximum allowable sourcing level programmed by MAXI, the output

remains switched on, and the fault timer starts charging CT. Once CT charges

to 2.5V, the output device is turned off and attempts either a retry sometime

later or waits for the state on the LATCH pin to change if in latch mode. When

the output current reaches the maximum sourcing current level, the output de-

vice appears as a current source.

application

INFO

available