LTC1558-5 Linear Technology, LTC1558-5 Datasheet - Page 16

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

LTC1558-3.3/LTC1558-5
TYPICAL APPLICATIONS
Typical “Medium Voltage” Application
The maximum main battery voltage is more than the
maximum V
needed for most notebook computers that have 3-cell or
4-cell series connected lithium battery packs.
The Schottky diode D11 (1N5818) prevents the main
battery’s high terminal voltage from overstressing the
LTC1558’s V
internal Zener inside the LTC1558 will clamp V
when the 1N5818’s reverse bias leakage current
increases at high temperature.
16
51pF
C
C1
100pF
C2
BAK
BAK
pin voltage (12V). This configuration is
R
10k
pin during nonbackup conditions. An
C
C
330pF
C
+
C
68pF
OSC
C2
1 F
C
0.1 F
SS
PUSHBUTTON
7V TO 18V
BATTERY
LTC1558-5 Medium Main Battery Voltage (7V to 18V) Application
9
4
6
3
2
1
RESET
MAIN
U
EXTV
SFB
V
I
RUN/SS
C
TH
OSENSE
OSC
SGND
V
IN
LTC1435
CC
13
5
R14
14k
SENSE
SENSE
PGND
INTV
BOOST
TG
P-CHANNEL
16
SW
10
Si4431DY
BG
CC
+
–
BACKUP
BATTERY
1.2V
NiCd
Q11
BAK
14
15
12
8
7
11
+
to 12V
D1 CMDSH-3
+
C3
4.7 F
16V
R11
422k
1%
R12
100k
1%
C11
47 F
6.3V
C5
1000pF
22 H
L11
3
2
4
0.1 F
A 100k pull-up resistor enables the LTC1558’s open-drain
BACKUP pin to turn the external P-channel MOSFET off
during backup mode, even when V
The main battery pack should have an internal control to
shut itself down once its energy is used up. This prevents
the lithium cells from deep discharge damage. Once the
main battery shuts down, the FB voltage drops and the
LTC1558 switches to backup mode.
C4
†
CTL
GND
FB
LTC1558-5
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
+
R13
100k
D2
MBRS140T3
10 H
C
22 F
35V
L1*
IN
2
D11
1N5818
+
R
0.033
SENSE
C12
1 F
**
R6
11k
1%
+
BAK
C
100 F
10V
OUT
2
is higher than V
35.7k
100pF
RESET
BACKUP
1%
R1
C6
1558 TA04
V
5V
3A
OUT
CC
.