LTC3703-5 Linear Technology, LTC3703-5 Datasheet - Page 17

• Manufacturer Part Number: LTC3703-5
• Description: 60V Synchronous Switching Regulator Controller
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
current to flow at full reverse voltage. If the reverse
current times reverse voltage exceeds the maximum
allowable power dissipation, the diode may be damaged.
For best results, use an ultrafast recovery diode such as
the MMDL770T1.
An internal undervoltage lockout (UVLO) monitors the
voltage on DRV
sufficient gate drive voltage. If the DRV
R1
R2
Figure 9c. Secondary Output Loop and V
V
DRV
CC
Figure 9a. V
OPTIONAL V
CONNECTION
5V < V
V
DRV
FCB
GND
CC
LTC3703-5
CC
+
CC
LTC3703-5
SEC
< 15V
BGRTN
1 F
CC
BGRTN
SW
V
BG
TG
CC
CC
IN
TG1
BG1
SW
V
IN
Generated from 5V < V
U
to ensure that the LTC3703-5 has
V
IN
V
+
IN
U
+
C
IN
C
L1
IN
N
1
W
5.1V
T1
OUT
CC
5.1V
CC
Connection
< 15V
voltage falls
+
U
+
+
37035 F09a
V
5V TO
15V
C
3703 F09c
OUT
OUT
V
1 F
C
V
OUT
SEC
OUT
V
DRV
below the UVLO threshold, the LTC3703-5 shuts down
and the gate drive outputs remain low.
Bottom MOSFET Source Supply (BGRTN)
The bottom gate driver, BG, switches from DRV
where BGRTN can be a voltage between ground and –5V.
Why not just keep it simple and always connect BGRTN to
ground? In high voltage switching converters, the switch
CC
5.1V
CC
LTC3703-5
Figure 9d. Capacitive Charge Pump for V
+
V
DRV
CC
BGRTN
Figure 9b. V
CC
LTC3703-5
1 F
SW
V
BG
TG
C
IN
IN
+
BGRTN
V
SW
V
BG
TG
C
IN
IN
IN
CC
+
V
Generated from V
IN
C10
1 F
10V
(<40V)
L1
ZHCS400
R17
37.4k
1%
R17
12.1k
1%
BAT85
D2
5.1V
L1
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FB
SW
VN2222LL
LTC3703-5
LT1613
OUT
4.7 H
+
GND
L2
0.22 F
CC
< 5V
SHDN
C
(V
OUT
V
IN
IN
+
CC
< 40V)
to BGRTN
BAT85
BAT85
C
3703 F09d
V
17
OUT
OUT
3703 F09b
V
<5V
OUT
37035f
C9
4.7 F
6.3V