Datasheet

PIN DESCRIPTION
UCC284-EP
www.ti.com ....................................................................................................................................... SLVS862A – NOVEMBER 2008 – REVISED NOVEMBER 2008
ELECTRICAL CHARACTERISTICS (continued)
T
A
= – 55 ° C to 100 ° C for the UCC284, VIN = VOUT – 1.5 V, I
OUT
= 0 mA, C
OUT
= 4.7 µ F, and CT = 0.015 µ F. For
UCC284-ADJ, VOUT is set to – 3.3 V (unless otherwise noted)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
I
OUT
0.5 A, VOUT = – 3.15 V 0.25 0.5 V
Dropout voltage, VOUT - VIN
I
OUT
50 mA, VOUT = – 3.15 V 25 50 mV
Sense pin input current 100 250 nA
UCC284-ADJ Adjustable 0.5-A Power Supply Section
Input voltage range – 15 – 3.5 V
Undervoltage lockout – 3.2 – 2.95 – 2.7 V
Quiescent current charge pump on VIN = – 3.15 V
(2)
200 350 µ A
Quiescent current VIN = – 15 V 200 250 µ A
VIN = – 13 V, SD/CT = 0 V
15 45 µ A
T
A
= 0 ° C to 100 ° C
(3)
Quiescent current in shutdown
VIN = – 13 V, SD/CT = 0 V
100 µ A
T
A
= – 55 ° C to 0 ° C
(3)
Shutdown threshold At shutdown pin (SD/CT) – 1.0 – 0.7 – 0.4 V
Shutdown input current SD/CT = 0 V 5 10 25 µ A
Output leakage in shutdown VIN = – 15 V, VOUT = 0 V
(4)
1 50 µ A
Overtemperature shutdown 140 ° C
Overtemperature hysteresis 20 ° C
UCC284-ADJ Adjustable 0.5-A Current Limit Section
Peak current limit VOUT = 0 V 0.7 1.1 1.5 A
Overcurrent threshold 0.55 0.7 0.9 A
Current limit duty cycle VOUT = 0 V 2.5 4 %
Overcurrent time out, t
ON
VOUT = 0 V 300 500 700 µ s
(2) The internal charge pump is enabled only for dropout condition with low VIN. Only in this condition is the charge pump required to
provide additional output FET fate drive to maintain dropout specifications. For conditions where the charge pump is not required, it is
disabled, which lowers overall device power consumption.
(3) Ensured by design. Not production tested.
(4) In the application during shutdown mode, output leakage current adds to quiescent current.
GND: This is the low noise ground reference input. All voltages are measured with respect to the GND pin.
SD/CT: This is the shutdown pin and also the short-circuit timing pin. Pulling this pin more positive than – 0.7 V
puts the circuit in a low-current shutdown mode. Placing a timing capacitor between this pin and GND sets the
short-circuit charging time, t
ON
during an overcurrent condition. During an overcurrent condition, the output pulses
at approximately a 2.5% duty cycle.
NOTE:
The CT capacitor must be connected between this pin and GND, not VIN, to assure
that the SD/CT pin is not pulled significantly negative during power-up. This pin
should not be externally driven more negative than – 5 V or the device will be
damaged.
VIN: This is the negative input supply. Bypass this pin to GND with at least 1 µ F of low ESR or ESL capacitance.
VOUT: Regulated negative-output voltage. A single 4.7 – µ F capacitor should be connected between this pin and
GND. Smaller value capacitors can be used for light loads, but this degrades the load-step performance of the
regulator.
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Product Folder Link(s): UCC284-EP