1.5A Very L.D.O Voltage Regulator
LM29150/1/2/3
Minimum Load Current
The LM29150 regulators are specified between finite loads. If the output is too small, leakage
currents is too small, leakage currents dominate and the output voltage rises. The 5mA minimum
load current swamps any expected leakage current across the operating temperature range.
Adjustable Regulator Design
Figure 4.
Adjustable Regulator with Resistors
VOUT=1.240V x [ 1+(R1/R2)]
The adjustable regulator versions, LM29152 and LM29153, allow programming the output voltage
anywhere between 1.25V and the 26V maximum operating rating of the family.
Two resistors are used. Resistors can be quite large, up to 1MΩ, because of the very high input
impedance and low bias current of the sense comparator: The resistor values are calculated by:
Where is VO the desired output voltage. Figure 4 shows component definition. Applications with
widely varying load currents may scale the resistors to draw the minimum load current required for
proper operation.
Error Flag
LM29151 and LM29153 versions feature and Error Flag, which looks at the output voltage and
signals and error condition when this voltage and signals an error condition when this voltage
drops 5% below its expected value. The error flag is an open-collector output that pulls low
under fault conditions. It may sink 10mA. Low output voltage signifies a number of possible
problems, including an over-current fault (the device is in current limit) and low input voltage.
The flag output is inoperative during over temperature shutdwon conditions.
Enable input
LM29151 and LM29152 versions feature and enable (EN) input that allows ON/OFF control of the
device. Special design allows "zero" current drain when the device is disabled-only microamperes
of leakage current flows. The EN input has TTL/CMOS compatible thresholds for simple interfacing
with logic, or may be directly tied to ≤ 30V. Enabling the regulator requires approximately 20uA of
current.
Mar. 2006-Rev06
HTC
98
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
