Datasheet

LT8705
39
8705fb
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Figure 14. Telecom Voltage Stabilizer
8705 F14a
CSPOUT
CSNOUT
EXTV
CC
FBOUT
INTV
CC
GATEV
CC
SRVO_FBIN
SRVO_FBOUT
SRVO_IIN
SRVO_IOUT
IMON_IN
IMON_OUT
SYNCCLKOUT
V
C
56.2k
202kHz
CSNIN
TG1 BOOST1
L1
22µH
M4
M1
×2
C
IN2
4.7µF
×4
SW1 BG1 CSP CSN
LT8705
GND BG2 SW2 BOOST2
V
OUT
48V
5A
V
IN
36V TO 80V
TG2
CSPIN
V
IN
SHDN
SWEN
LDO33
MODE
FBIN
RT
SS
3.3nF220pF
C
IN1
, C
OUT2
: 220µF, 100V
C
IN2
, C
OUT1
: 4.7µF, 100V, TDK C453X7S2A475M
D
B1
, D
B2
: CENTRAL SEMI CMMR1U-02-LTE
L1: 22µH, WÜRTH 74435572200 OR COILCRAFT SER2918H-223
M1, M3: FAIRCHILD FDMS86104
M2, M4: FAIRCHILD FDMS86101
*2Ω FROM TG1 TO EACH SEPERATE M1 GATE
**2Ω FROM BG2 TO EACH SEPERATE M3 GATE
215k
71.5k
100k
20k
1µF
1µF
4.7µF
10k
392k
C
IN1
220µF
×2
C
OUT1
4.7µF
×6
4Ω
D
B1
D
B2
4.7µF
TO
BOOST1
4.7µF
+
C
OUT2
220µF
×2
+
TO
BOOST2
0.22µF 0.22µF
TO
DIODE D
B1
TO
DIODE D
B2
M2
M3
×2
1nF
1nF
2Ω*
2Ω**
10mΩ
10Ω
10Ω
LOAD CURRENT (mA)
10
0
EFFICIENCY (%)
20
30
40
50
60
70
100
1000
8705 F14b
80
90
100
10
10000
COILCRAFT SER2918H-223
WURTH 74435572200
V
IN
= 36V
V
OUT
= 48V
CCM
LOAD CURRENT (mA)
10
0
EFFICIENCY (%)
20
30
40
50
60
70
100
1000
8705 F14c
80
90
100
10
10000
COILCRAFT SER2918H-223
WURTH 74435572200
V
IN
= 72V
V
OUT
= 48V
CCM
Efficiency vs Output Current
(Boost Region)
Efficiency vs Output Current
(Buck Region)
Note: See the front page and the Typical Performance Characteristics section for more curves from this application
circuit using the Coilcraft inductor. The smaller Würth inductor is also suitable in place of the Coilcraft inductor with
some loss in efficiency.
applicaTions inForMaTion