MIC5157 Micrel Semiconductor, MIC5157 Datasheet - Page 11

• Manufacturer Part Number: MIC5157
• Description: Mic5156, Mic5157, And Mic5158 Super Ldo? Regulator Controller
• Manufacturer: Micrel Semiconductor

August 2005
MIC5156/5157/5158
Figure 5. Battery Charger Concept
E N
MIC5158
GND
V
DD
E A
G
D
S
R 1
R 2
V
IN
R 3
R 4
11
Uninterruptible Power Supply
The MIC5157 and two N-channel MOSFETs provide battery
switching for uninterruptible power as shown in figure (6).
Two MOSFETs are placed source-to-source to prevent cur-
rent flow through their body diodes when switched off. The
Super LDO regulator is continuously enabled to achieve
fast battery switch-in. Careful attention must be paid to the
ac-line monitoring circuitry to ensure that the output voltage
does not fall below design limits while the battery is being
switched in.
Line
Battery
A C
Line
Figure 6. UPS Power Supply Concept
EN
Power Supply
MIC5158
Off-line
GND
V
DD
1N4148
E A
G
D
S
Q1
Q2
G
G
D
S
S
D
40V max.
MOSFET body diodes
shown for clarity
MIC5156/5157/5158
Uninterruptable
D C
Micrel, Inc.