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| LTC3703_15 Datasheet, PDF (17/34 Pages) Linear Technology – 100V Synchronous Switching Regulator Controller | |||
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Applications Information
VIN
+
1µF
VIN
LTC3703
TG
VCC
SW
DRVCC
BG
+
CIN
12V
L1
VOUT
10V TO
15V
+
COUT
BGRTN
3703 F10a
Figure 10a. VCC Generated from 10V < VOUT < 15V
LTC3703
VIN
+
12V
CIN
VIN
LTC3703
TG
VCC
SW
DRVCC
BG
BGRTN
D2
ZHCS400
L2
10µH
C10
1µF R17
16V
1M
1%
SW LT1613 VIN
FB
SHDN
R17
GND
110k
1%
C9
4.7µF
6.3V
L1
VOUT
<10V
+
COUT
3703 F10b
Figure 10b. VCC Generated from VOUT < 10V
OPTIONAL VCC
CONNECTION
10V < VSEC < 15V
VIN
LTC3703
VCC
TG1
DRVCC
R1
FCB
R2
GND
SW
BG1
BGRTN
VIN
+
CIN
12V
N
T1
1
+ VSEC
1µF
VOUT
+
COUT
3703 F10c
Figure 10c. Secondary Output Loop and VCC Connection
+
1µF
VIN (<40V)
+
CIN
VIN
LTC3703
TG
12V
BAT85
0.22µF
VN2222LL
BAT85
BAT85
VCC
SW
DRVCC
BG
VOUT
L1
+
COUT
BGRTN
3703 F10d
Figure 10d. Capacitive Charge Pump for VCC (VIN < 40V)
above the input supply: VBOOST = VIN + VDRVCC. The value
of the boost capacitor, CB, needs to be 100 times that
of the total input capacitance of the topside MOSFET(s).
The reverse breakdown of the external diode, DB, must be
greater than VIN(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 DRVCC to ensure that the LTC3703 has sufficient
gate drive voltage. If the DRVCC voltage falls below the
UVLO threshold, the LTC3703 shuts down and the gate
drive outputs remain low.
3703fc
17
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