LTC1558-5 Linear Technology, LTC1558-5 Datasheet - Page 17

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

TYPICAL APPLICATIONS
Typical “High Voltage” Application
The maximum main battery voltage is 48V.
The Schottky diode D11 (MBR170) prevents the main
battery’s high terminal voltage from overstressing the
LTC1558’s V
internal Zener inside the LTC1558 will clamp V
when the MBR170’s reverse bias leakage current
increases at high temperature.
As shown above, the design must ensure that V
not force the external P-channel MOSFET’s V
maximum rating (15V for the MTD2955E) shown during
nonbackup mode.
2N3906
P-CHANNEL
MTD2955E
MAIN
BATTERY
48V
Q12
Q11
100k
BAK
R16
+
pin during nonbackup conditions. An
R15
100k
R11
422k
1%
R12
100k
1%
Z11
12V
C3
3.3 F
D1
1N4148
C1
0.047 F
C4
470pF
U
LTC1558-5 High Main Battery Voltage (48V) Application
R
1k
C
C2
0.068 F
C
3300pF
C
**IRC LR2512-01-RO40-5
*HURRICANE LAB HL-KI168M
†
1
2
3
4
5
6
7
8
SUMIDA CD54-220
D11
MBR170
GS
PGATE
V
V
P-DRIVE
V
C
I
SENSE
TH
IN
CC
CC
T
BAK
above its
BAT
LTC1149-5
–
to 12V
SHUTDOWN 2
SHUTDOWN 1
does
R14
14k
RESET
PUSHBUTTON
SENSE
NGATE
RGND
PGND
SGND
1N4148
CAP
+
D2
During nonbackup mode, the LTC1558’s open-drain
BACKUP pin is low. The external 12V Zener and 2N3906
conduct and the MTD2955E’s V
mately 12V. During backup, the BACKUP pin floats and the
2N3906’s base voltage is pushed nearer to V
MTD2955E is effectively turned off, isolating the main
battery from V
The main battery pack should have an internal control to
shut itself down once its energy is used up. This prevents
it from deep discharge damage.
BACKUP
BATTERY
1.2V
NiCd
16
15
14
13
12
11
10
9
+
C5
1000pF
SHUTDOWN
C11
47 F
6.3V
LTC1558-3.3/LTC1558-5
Q2
N-CHANNEL
IRFZ34
22 H
Q1
P-CHANNEL
MTD2955E
L11
BAK
3
2
†
GND
CTL
during backup.
LTC1558-5
68 H
L1*
100
SW
BACKUP
R4
FB
RESET
+
1
4
V
100
V
BAK
R3
CC
D3
MBR380
C
100 F
100V
IN
7
8
5
6
GS
R
0.04
SENSE
is clamped at approxi-
C6
0.1 F
+
**
1558 TA05
+
C12
1 F
C
220 F
10V
OS-CON
OUT
RESET
BACKUP
V
5V
2.5A
BAK
OUT
17
. The