Datasheet

MAX17595/MAX17596/MAX17597
Peak-Current-Mode Controllers for
Flyback and Boost Regulators
15Maxim Integrated
error amplifier is set up as a proportional gain amplifier
as shown in Figure 9.
Programming Output Voltage
The devices incorporate an error amplifier with a 1% pre-
cision voltage reference that enables negative feedback
control of the output voltage. The output voltage of the
switching converter can be programmed by selecting the
values for the resistor-divider connected from V
OUT
, and
the flyback/boost output to ground, with the midpoint of
the divider connected to the FB pin (Figure 7). With R
B
selected in the 20kI to 50kI range, R
U
can be calcu-
lated as:
OUT
UB B
V
R R 1 k , where R is in k .
1.21

=×−


II
Peak-Current-Limit Setting (CS)
The devices include a robust overcurrent protection scheme
that protects the device under overload and short-circuit
conditions. A current-sense resistor, connected between
the source of the MOSFET and PGND, sets the peak
current limit. The current-limit comparator has a voltage
Figure 6. MAX17596/MAX17597 Typical Startup Circuit with Bias Winding to Turn Off Q1 and Reduce Power Dissipation
Figure 5. MAX17596/MAX17597 Typical Startup Circuit with V
IN
Connected Directly to DC Input
V
DRV
V
DC
C
OUT
C
DRV
Np Ns
D1
V
IN
V
IN
V
OUT
R
S
CS
NDRV
LDO
MAX17596
MAX17597
DRV
V
DRV
V
DC
C
OUT
C
DRV
Np
NB
Ns
D1
V
IN
V
IN
R
Z
Z
D1
6.3V
C
IN
R
S
CS
NDRV
MAX17596
MAX17597
LDO
Q
1
DRV
D2