UCC281-3_09 Datasheet, PDF (1/12 Pages) Texas Instruments – Low Dropout 1 Ampere Linear Regulator Family

UCC281-3/-5/-ADJ
UCC381-3/-5/-ADJ
Low Dropout 1 Ampere Linear Regulator Family
FEATURES
• Precision Positive Linear Voltage
Regulation
• 0.5V Dropout at 1A
• Guaranteed Reverse Input/ Output
Voltage Isolation with Low Leakage
• Low Quiescent Current Irrespective of
Load
• Adjustable Output Voltage Version
• Fixed Versions for 3.3V and 5V
Outputs
• Logic Shutdown Capability
• Short Circuit Power Limit of
3% • V_IN • Current Limit
• Remote Load Voltage for Accurate
Load Regulation
DESCRIPTION
The UCC381-3/-5/-ADJ family of positive linear series pass regulators is
tailored for low drop out applications where low quiescent power is impor-
tant. Fabricated with a BiCMOS technology ideally suited for low input to
output differential applications, the UCC381 will pass 1A while requiring
only 0.5V of input voltage headroom. Dropout voltage decreases linearly
with output current, so that dropout at 200mA is less than 100mV. Quies-
cent current is always less than 650µA. To prevent reverse current conduc-
tion, on-chip circuitry limits the minimum forward voltage to typically 50mV.
Once the forward voltage limit is reached, the input-output differential volt-
age is maintained as the input voltage drops until undervoltage lockout dis-
ables the regulator.
UCC381-3 and UCC381-5 versions have on-chip resistor networks preset
to regulate either 3.3V or 5.0V, respectively. Furthermore, remote sensing
of the load voltage is possible by connecting the VOUTS pin directly at the
load. The output voltage is then regulated to 1.5% at room temperature and
better than 2.5% over temperature. The UCC381-ADJ version has a regu-
lated output voltage programmed by an external user-definable resistor ra-
tio.
(continued)
BLOCK DIAGRAM
VIN 8
1.3/2.1A
CURRENT
REFERENCE
CURRENT
LIMIT
–
+
SHUTDOWN FOR FIXED VERSIONS
CT* 5
0.65V
*ADJ
VERSION
ONLY
3% DUTY CYCLE
CURRENT LIMIT TIMER
REVERSE VOLTAGE
SENSE
THERMAL
SHUTDOWN
SLUS214B -JANUARY 2001
V_PUMP
UVLO
VOLTAGE
AMPLIFIER
R2
–
+
1.25V
R1
1 VOUT
4 VOUTS
2 GND
3 GND
6 GND
7 GND
UCC381-ADJ
UCC381-3
UCC381-5
R2 R1
0 OPEN
82k 50k
150k 50k
UDG-98112