UCC284- Datasheet, PDF (1/10 Pages) Texas Instruments – Low Dropout 0.5A Negative Linear Regulator

Low Dropout 0.5A Negative Linear Regulator
FEATURES
• Precision Negative Series
Pass Voltage Regulation
BLOCK DIAGRAM
• 0.2V Drop Out at 0.5A
• Wide Input voltage Range
–3.2V to –15V
• Low Quiescent Current
1µA
DISCHARGE
–0.6V
+
–
50k
SHUTDOWN ^–2.2V
1.25V
Irrespective of Load
+
• Simple Logic Shutdown
Interfacing
SD/CT 8
–1.6V –
–2.6V +
SQ
RQ
TON
TOFF
• –5V, –12V and Adjustable
–
Output
• 2.5% Duty Cycle Short Circuit
Protection
40µA
CHARGE
OVERCURRENT
700mA –
• Remote Load Sensing for
VIN 2
Accurate Load Regulation
VIN 3
+
THERMAL
SHUTDOWN
• 8-Pin DP Package
VIN 6
UVLO
VIN 7
(–)
UCC284-5/-12/-ADJ
UCC384-5/-12/-ADJ
UCC384-ADJ
UCC384-5
UCC384-12
R1 R2
0 OPEN
375K 125K
375K 43.6K
(+)
4 GND
R2
VPUMP
+
GM
–
R1
1 VOUTS
5 _VOUT
(–)
UDG-99030
DESCRIPTION
The UCC384 family of negative linear series pass regula-
tors is tailored for low drop out applications where low
quiescent power is important. Fabricated with a
BCDMOS technology ideally suited for low input to out-
put differential applications, the UCC384 will pass 0.5A
while requiring only 0.2V of input voltage headroom.
Drop out voltage decreases linearly with output current,
so that drop out at 50mA is less than 20mV.
Quiescent current consumption for the device under nor-
mal (non-drop out) conditions is typically 200µA. An inte-
grated charge pump is internally enabled only when the
device is operating near drop out with low VIN. This
guarantees that the device will meet the drop out specifi-
cations even for maximum load current and a VIN of
–3.2V with only a modest increase in quiescent current.
Quiescent current is always less than 350µA, with the
charge pump enabled. Quiescent current of the UCC384
does not increase with load current.
SLUS234A - JANUARY 2000
Short circuit current is internally limited. The device re-
sponds to a sustained over current condition by turning
off after a T_ON delay. The device then stays off for a pe-
riod, T_OFF, that is 40 times the T_ON delay. The device
then begins pulsing on and off at the T_ON/T_OFF duty cycle
of 2.5%. This drastically reduces the power dissipation
during short circuit such that heat sinking, if at all re-
quired, must only accommodate normal operation. An
external capacitor sets the on time. The off time is al-
ways 40 times T_ON.
The UCC384 can be shutdown to 45µA (maximum) by
pulling the SD/CT pin more positive than –0.6V. To allow
for simpler interfacing, the SD/CT pin may be pulled up
to +6V above the ground pin without turning on clamping
diodes.
Internal power dissipation is further controlled with ther-
mal overload protection circuitry. Thermal shutdown oc-
curs if the junction temperature exceeds 140°C. The chip
will remain off until the temperature has dropped 20°C.