LM2575 & LM2576
POWER MANAGEMENT
Applications Information - Inverting Buck/Boost
LM2575
LM2576
CIN
D1
47µF
3A
100µF
7A
L1
100µH
2,700µF
250mA
68µH
COUT
IOUT
6,800µF
500mA
LM2575
LM2576
CIN
D1
47µF
3A
100µF
7A
L1
100µH
470µF
100mA
68µH
COUT
IOUT
2,700µF
750mA
Inverting buck/boost operation is a different topology of Component stress requirements are very similar to the
operation than buck. This difference reduces the output buck with a few exceptions:
current capability of the device, in that the inductor must
supply all of the load current during the time the power (1) catch diode breakdown VBR must be greater than
switch is off. Maximum output current is approximately: VIN + |VOUT|
(2) input capacitor is larger due to the increased peak
current during switch turn on. Power dissipation is
approximately:
3.5
IOUT
≈
≈
(LM2576 )
(LM2575 )
VO
VIN
2
1+
VO
VO
VIN
VO
VIN
PD
≈
IO 1 +
VSAT + 0 .02 VIN
VO + VIN
1.3
IOUT
VO
VIN
Please contact factory for additional assistance when
using the buck/boost topology.
2 1+
ã 2001 Semtech Corp.
15
www.semtech.com
SEMTECH [ SEMTECH CORPORATION ]
