Datasheet

LTC3703
17
3703fc
applicaTions inForMaTion
above the input supply: V
BOOST
= V
IN
+ V
DRVCC
. The value
of the boost capacitor, C
B
, needs to be 100 times that
of the total input capacitance of the topside MOSFET(s).
The reverse breakdown of the external diode, D
B
, must be
greater than V
IN(MAX)
. Another important consideration
for the external diode is the reverse recovery and reverse
leakage, either of which may cause excessive reverse cur-
rent 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 silicon diode such as
the BAS19.
An internal undervoltage lockout (UVLO) monitors the volt-
age on DRV
CC
to ensure that the LTC3703 has sufficient
gate drive voltage. If the DRV
CC
voltage falls below the
UVLO threshold, the LTC3703 shuts down and the gate
drive outputs remain low.
V
CC
DRV
CC
V
IN
TG
SW
BG
BGRTN
LTC3703
V
OUT
10V TO
15V
+
C
OUT
3703 F10a
+
C
IN
+
1µF
V
IN
L1
12V
V
CC
DRV
CC
V
IN
TG
SW
BG
BGRTN
LTC3703
V
OUT
<10V
+
C
OUT
3703 F10b
+
C
IN
C9
4.7µF
6.3V
V
IN
L1
12V
C10
1µF
16V
V
IN
SW
GND
SHDN
FB
R17
1M
1%
R17
110k
1%
LT1613
D2
ZHCS400
L2
10µH
V
CC
DRV
CC
FCB
GND
V
IN
TG1
SW
BG1
BGRTN
LTC3703
V
OUT
V
SEC
+
C
OUT
+
1µF
3703 F10c
R1
V
IN
T1
OPTIONAL V
CC
CONNECTION
10V < V
SEC
< 15V
R2
+
C
IN
12V
N
1
V
CC
DRV
CC
V
IN
TG
SW
BG
BGRTN
LTC3703
V
OUT
+
C
OUT
3703 F10d
+
+
C
IN
V
IN
(<40V)
L1
1µF
12V
BAT85
BAT85
BAT85
VN2222LL
0.22µF
Figure 10a. V
CC
Generated from 10V < V
OUT
< 15V
Figure 10b. V
CC
Generated from V
OUT
< 10V
Figure 10c. Secondary Output Loop and V
CC
Connection
Figure 10d. Capacitive Charge Pump for V
CC
(V
IN
< 40V)