Voltage Regulators
s
Pin Descriptions
Pin No. Pin name
1
TR
I/O
I
Explanation
Transformer reset detection input. When the
IC detects transformer resetting and the fall-
ing edge of a high-level signal is input to
this pin of the AN8037 or a low-level signal
is input to the same pin of the AN8027, the
level of the Out pin becomes high. However,
the transformer reset signal is ignored if the
signal is shorter than the minimum off-pe-
riod determined by the CF pin. Also note
that the maximum on-period is corrected ac-
cording to the source currents.
Connection for the resistor that determines
the overload level of the IC to activate the
timer latch protection circuit.
By judging the operating mode (i.e., the nor-
mal or standby mode) of the IC from the
secondary side, the timer period is adjusted
with the selection of external resistance ac-
cording to the operating mode.
Connection for the capacitor that determines
the on- and off-periods of the IC output (Out).
The on- and off-periods are corrected by I
ON
which is proportional to the flowing out cur-
rent at the TR pin, and I
OFF
which corre-
sponds to the current at FB pin.
AN8027, AN8037
Equivalent Circuit
V
REF
1
High-side Low-side
clamp clamp
2
OCP
V
REF
Comp.
CF
2
3
CF
V
REF
I
OFF
Comp.
V
FB
I
ON
3
4
CLM
I
Input to the pulse-by-pulse overcurrent pro-
tection circuit.
Normally, we recommend adding an external
filter for this input. If overcurrent continues
for several cycles, the IC determines that the
operation is erroneous, thus triggering the
latch protection function.
IC ground.
V
REF
Comp.
CLM(−) 4
5
GND
5
5
PANASONIC [ PANASONIC SEMICONDUCTOR ]
