LTC1558-5 Linear Technology, LTC1558-5 Datasheet - Page 15

• Manufacturer Part Number: LTC1558-5
• Description: Backup Battery Controller with Programmable Output
• Manufacturer: Linear Technology

TYPICAL APPLICATIONS
Typical “Low Voltage” Application
The maximum main battery voltage is less than the maxi-
mum V
lowest number of external components.
The LTC1435’s minimum input voltage is 3.5V. The V
voltage, set by R11 and R12, is programmed to 3.8V.
Therefore, the main battery’s lowest voltage should be
3.8V + 1 body diode drop = 4.5V. This will enable a fresh
51pF
BAK
C
C1
100pF
C2
pin voltage (12V). This configuration has the
R
10k
C
C
330pF
C
+
C
68pF
OSC
C
0.1 F
C2
1 F
SS
PUSHBUTTON
4.5V TO 10V
BATTERY
LTC1558-3.3 Low Main Battery Voltage (4.5V to 10V) Application
9
4
6
3
2
1
RESET
MAIN
U
EXTV
SFB
V
I
RUN/SS
C
TH
OSENSE
OSC
SGND
V
IN
CC
LTC1435
13
5
R14
14k
SENSE
SENSE
PGND
INTV
BOOST
TG
P-CHANNEL
16
SW
10
Si4431DY
BG
CC
+
–
BACKUP
BATTERY
1.2V
NiCd
Q11
14
15
12
8
7
11
+
D1 CMDSH-3
+
BAK
C3
4.7 F
16V
R11
221k
1%
R12
100k
1%
C11
47 F
6.3V
C5
1000pF
22 H
L11
3
2
4
0.1 F
main battery to turn on the external P-channel MOSFET
and power up the system out of UVLO during cold power
boot or out of backup mode when the LTC1558 is power-
ing up the system.
A 100k pull-up resistor enables the open-drain BACKUP
pin to turn the external P-channel MOSFET off when V
is higher than V
C4
†
CTL
GND
FB
LTC1558-3.3
Q1
N-CHANNEL
Si4412DY
Q2
N-CHANNEL
Si4412DY
SW
BACKUP
RESET
1
V
V
BAK
CC
**
*
†
SUMIDA CDRH125-10
IRC LR2D1D-01-RQ33-F
SUMIDA CD54-220
7
8
5
6
LTC1558-3.3/LTC1558-5
+
R13
100k
CC
D2
MBRS140T3
10 H
.
C
22 F
35V
L1*
IN
2
+
R
0.033
SENSE
C12
1 F
**
R5
20k
1%
+
C
100 F
10V
IN
2
100pF
35.7k
RESET
BACKUP
1%
R1
C6
1558 TA03
V
3.3V
3A
OUT
15
BAK