S-8365AAABA-M5T1Y2 Datasheet, PDF (16/63 Pages) Seiko Instruments Inc – PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER

STEP-UP, SUPER-SMALL PACKAGE, 1.2 MHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8365/8366 Series
Rev.2.1_01
4. Timer latch type short-circuit protection (products with short-circuit protection function)
The S-8365/8366 Series incorporates a timer latch type short-circuit protection circuit that stops switching operation
if the output short circuits for a certain time or more. Connect a capacitor (CSP) to the CSP pin to set the delay time
of this circuit.
The S-8365/8366 Series operates on the maximum duty if the output voltage drops due to output short-circuiting or
other factors. When it enters the maximum duty status, charging the constant current to CSP is started. If this
status is held for the short-circuit protection delay time or more, the voltage of the CSP pin exceeds the reference
voltage and the IC enters the latch mode.
Note that switching operation stops in latch mode but the internal circuits normally operate, which differs from the
power-off status. The constant current is continuously charged to CSP even in latch mode, so the voltage of the
CSP pin rises to the VDD level.
To reset the latch mode of short-circuit protection, lower VDD to the UVLO detection voltage or lower or set the ON/
OFF pin to the low level.
Input voltage ^{UVLO release}
(V_DD)
UVLO detection
Output load
Short-circuit state
CSP pin
voltage
(V_CSP)
Latch mode
Reference
voltage
50 ms (CSP = 0.1 μF)
Normal
state
Short circuit protection
delay time
Latch
period
Short-circuit protection Short-circuit protection
delay time
delay time
Reset period
Reset period
Figure 13
5. UVLO function (products with UVLO function)
The S-8365/8366 Series has a UVLO (undervoltage lockout) circuit for avoiding IC malfunctions due to power
supply voltage drops. The S-8365/8366 Series stops switching operation upon UVLO detection and retains the
external transistor in the off state. After entering the UVLO detection status once, the soft-start function is reset.
Note, however, that the other internal circuits operate normally and that the status differs from the power-off status.
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