MIC29710_06 Datasheet, PDF (9/11 Pages) Micrel Semiconductor – 7.5A Fast-Response LDO Regulator

Micrel, Inc.
Adjustable Regulator Design
The adjustable regulator version, MIC29712, allows pro-
gramming the output voltage anywhere between 1.25V
and the 16V maximum operating rating of the family.
Two resistors are used. Resistors can be quite large, up
to 100kΩ, because of the very high input impedance and
low bias current of the sense comparator. The resistor
values are calculated by:
R1 =
R2 ×
⎜⎜⎝⎛
V_OUT
1.240
− 1_{⎟⎟⎠⎞}
Where V_O is the desired output voltage. Figure 4 shows
component definition.
MIC29712BT
VIN
4.75 to 5.25
10µF
R1
100k
R2
56.2k
VOUT
3.45V
33µF
VOUT = 1.240V× [1 + (R1 / R2)]
Figure 4. Adjustable Regulator with Resistors
MIC29710/29712
Enable Input
The MIC29712 versions features an enable (EN) input
that allows ON/OFF control of the device. Special design
allows “zero” current drain when the device is disabled—
only micro-amperes of leakage current flows. The EN
input has TTL/CMOS compatible thresholds for simple
interfacing with logic, or may be directly tied to V_IN.
Enabling the regulator requires approximately 20µA of
current into the EN pin.
Minimum Load Current
The MIC29710/12 regulators are specified between finite
loads. If the output current is to small, leakage currents
dominate and the output voltage rises. A 10mA minimum
load current is necessary for proper regulation.
Voltage
2.85
2.9
3.0
3.1
3.15
3.3
3.45
3.525
3.6
3.8
4.0
4.1
Standard (Ω)
R1
R2
100k
76.8k
100k
75.0k
100k
69.8k
100k
66.5k
100k
64.9k
100k
60.4k
100k
56.2k
93.1k
51.1k
100k
52.3k
100k
48.7k
100k
45.3k
100k
43.2k
Figure 5. MIC29712 Resistor Table
October 2006
9
M9999-101906