LT8708
59
Rev 0
52V
Battery Backup Supply Using FHCM and RHCM
When V
IN
Is Not Applied, V
LOAD
Is Regulated to
47.4V
Until V
BAT
Drops Below
36V
When V
IN
Is Applied, V
BAT
Is Charged to
52.1V
APPLICATIONS INFORMATION
+
–
CSPOUT CSNOUT V
INCHIP
SHDN
FBOUT INT
V
CC
GA
TEV
CC
IMON_ON
IMON_OP
ICN ICP
IMON_INP IMON_INN CLKOUT
SYNC
SS
RT
V
C
MODE
CSNIN
TG1
BOOST1
SW1
BG1
CSP
CSN
LT8708
GND
BG2
SW2
BOOST2
TG2
CSPIN
EXT
V
CC
FBIN
VINHIMON
SWEN
LDO33
DIR
RVSOFF
150kHz
VOUTLOMON
+
+
D
B1
D
B2
TO
BOOST1
TO
BOOST2
TO DIODE
D
B1
V
BAT
8708 T
A05a
CHARGE VOL
TAGE:
52.1V
V
LOAD
TO DIODE
D
B2
L1: 10
μH, WUR
TH 701014101
M1
–M4: INFINEON BSC039N06NS
C
IN1
:
1200
μF
, 100V
C
OUT3
: 220
μF
, 100V
C
IN2
, C
IN3h
, C
OUT1
,
C
OUT2
: 4.7
µF
, 100V
, X7R
M5: TOSHIBA T2N7002AK
D
IN
:
APPROPRIA
TE 8A SCHOT
TKY DIODE OR IDEAL DIODE
SUCH AS L
TC4357.
D
B1
, D
B2
: CENTRAL SEMI CMMR1U-02-L
TE
V
IN
52V
D
IN
TO LOADS
(REGULA
TE TO
47.4V WHEN IN BACKUP)
127k
M5
54.9k
220pF
6.8nF
24.9k
294k
1μ
F
6.8
nF
26.7k
22
nF
17.4k
17.4k
6.8
nF
6.8
nF
22
nF
17.4k
17.4k
4.7
μF
4Ω
10k
4.7
μF
422k
1μ
F
10k
294k
C
OUT3
C
OUT2
C
OUT1
10m
Ω
2Ω
0.22
μF
M4
M2
M3
L1 10
μH
2Ω
5m
Ω
10
Ω
10
Ω
1nF
1nF
2Ω
0.22
μF
2Ω
M1
C
IN1
C
IN3
C
IN2
5m
Ω
0.73k
11.3k
464k
84.5k
100k
100k
4.7
μF
100k
V
BAT
37.5V TO 52.1V
+
–
10k
422k
CHARGE V
BA
T
TO
52.1V
LIMIT V
BAT
CHARGING
CURRENT TO 5A
10m
Ω
10m
Ω
POWER FLOW
8708 T
A05b
V
IN
52V
D
IN
52V LOADS
V
BAT
36V TO 52.1V
+
–
10k
294k
PREVENT
DISCHARGING
V
BAT
BELOW 35V
LIMIT V
LOAD
CURRENT
TO 5A WHEN
POWERED BY V
BAT
10m
Ω
10m
Ω
POWER FLOW
8708 T
A05c
V
IN
0V
D
IN
47.4V LOADS
SHDN
0.73k
11.3k
464k
REGULA
TE
V
LOAD
TO 47.4V
