 

     



SLUS198C – FEBUARY 2000 - REVISED - JUNE 2001

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

electrical characteristics, these specifications apply for T

= –40°C to 85°C for the UCC2915 and

0°C to 70°C for the UCC3915, VIN = 12 V, IMAX = 0.4 V, SHTDWN = 2.4 V, T

= T

, (unless otherwise

stated)

DAC (continued)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Trip c rrent

Code = 1110 2.30 2.75 3.25 A

Trip current

Code = 1111 2.50 3.0 3.50 A

Max output current over trip

(current source mode)

Code = 0100 to 1111, I

MAX

= 0 V 0.35 1.0 1.65 A

Max output current

(current source mode)

Code = 0100 to 1111, I

MAX

= 2.4 V 3.0 4.0 5.2 A

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

fault timer

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

CT charge current V

= 1.0 V –83 –62 –47 µA

CT discharge current V

= 1.0 V 0.8 1.2 1.8 µA

Output duty cycle V

OUT

= 0 V 1.0% 1.9% 3.3%

CT fault threshold 1.2 1.5 1.7 V

CT reset threshold 0.4 0.5 0.6 V

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

shutdown

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Shutdown threshold 1.1 1.5 1.9 V

Shutdown hysteresis 150 mV

Input current 100 500 nA

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

open drain output (FAULT)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

High level output current FAULT = 5 V 250 µA

Low level output voltage I

OUT

= 5 mA 0.2 0.8 V

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

TTL input dc characteristics

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

TTL input voltage high 2.0 V

TTL input voltage low 0.8 V

TTL input high current V

= 2.4 V 3 10 µA

TTL input low current V

= 0.4 V 1 µA

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

 

     



SLUS198C – FEBUARY 2000 - REVISED - JUNE 2001

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

pin descriptions

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 and adaptive-current limiting.

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

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

FAULT

= 16.1 × 10

× C

. Once the fault time is reached the output will shutdown for a time given by

= 833 × 10

× C

, this equates to a 1.9% duty cycle.

FAULT

: Open-drain output, which pulls low upon any fault or interrupt condition, or thermal shutdown.

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

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

applications which require fast charging of load capacitance.

SHTDWN

: When this pin is brought to a logic low, the IC is put into a sleep mode drawing typically less than

100 µA of I

.The input threshold is hysteretic, allowing the user to program a startup delay with an external

RC circuit.

VIN: Input voltage to the UCC3915. The recommended voltage range is 7 V to 15 V. Both VIN pins should be

connected together and connected to the power source.

VOUT: Output voltage from the UCC3915. Both VOUT pins should be connected together and connected to

the load. When switched the output voltage will be approximately V

– (0.15 Ω × I

OUT

). VOUT must not exceed

VIN by greater than 0.3 V.

APPLICATION INFORMATION

UDG-99175

6 7 8 9

B0B1B2B3 IMAX

4 12 13 5

1SHTDWN

VOUT

VIN

FAULT

GND

HEAT SINK

GND PINS

UCC3915

OUT

S1 S2 S3 S4 S5

DIP

SWITCH

LED5 V

Figure 1. Evaluation Circuit

 

     



SLUS198C – FEBUARY 2000 - REVISED - JUNE 2001

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

protecting the UCC3915 from voltage transients

The parasitic inductance associated with the power distribution can cause a voltage spike at V

if the load

current is suddenly interrupted by the UCC3915. It is important to limit the peak of this spike to less than 15 V

to prevent damage to the UCC3915. This voltage spike can be minimized by:

D Reducing the power distribution inductance (e.g., twist the positive (+) and negative (–) leads of the power

supply feeding V

, locate the power supply close to the UCC3915 or use PCB power and ground planes).

D Decoupling V

with a capacitor, C

(refer to Figure 1), located close to the V

pins. This capacitor is

typically 1 µF or less to limit the inrush current.

D Clamping the voltage at V

below 15 V with a Zener diode, D1(refer to Figure 1), located close to the V

pins.

Figure 2. Load Current, Timing-Capacitor Voltage, and Output Voltage of the UCC3915

Under Fault Conditions

estimating maximum load capacitance

For hot-swap applications, the rate at which the total output capacitance can be charged depends on the

maximum-output current available and the nature of the load. For a constant-current, current-limited

application, the output will come up if the load asks for less than the maximum available short-circuit current.

To ensure recovery of a duty cycle from a short-circuited load condition, there is a maximum total output

capacitance which can be charged for a given unit on time (fault time). The design value of on or fault time can

be adjusted by changing the timing capacitor C

Part #	UCC2915DP
Description	15V PROG HOT SWAP PWR MANAGER- Rail/Tube
Category	IC
Availability	In Stock
Qty	10

Qty	Price
1 - 2	$9.28557
3 - 4	$7.38625
5 - 6	$6.96417
7 - 8	$6.47176
9 +	$5.76831

UCC2915DP

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