S8337 datasheet(13/51 Pages) SII

13 / 51 page

STEP-UP, 1.2 MHz HIGH-FREQUENCY, PWM CONTROL SWITCHING REGULATOR CONTROLLER

Rev.4.0_01

S-8337/8338 Series

3. Shutdown pin (S-8338 Series only)

This pin stops or starts step-up operations.

Switching the shutdown pin to the “L” level stops operation of all the internal circuits and reduces the

current consumption significantly.

DO NOT use the shutdown pin in a floating state because it is not pulled up or pulled down internally.

DO NOT apply voltage of between 0.3 V and 1.8 V to the shutdown pin because applying such a

voltage increases the current consumption. If the shutdown pin is not used, connect it to the VIN pin.

Table 7

Shutdown Pin

CR Oscillator

Output Voltage

“H”

Operates

Fixed

“L”

Stopped

≅ VIN*1

*1. Voltage of VIN from which the voltage drop from the

DC resistance of the inductor and the forward

voltage of the diode are subtracted

ON/OFF

VIN

VSS

Figure 9

4. Timer latch short-circuit protection function

This IC has a timer latch short-circuit protection circuit that stops the switching operation when the

output voltage drops for a specific time due to output short-circuiting. A capacitor (CSP) that is used

to set the delay time of this short-circuit protection circuit is connected to the CSP pin.

This IC operates at the maximum duty ratio if the output voltage drops due to output short-circuiting.

At the maximum duty ratio, constant-current charging of CSP starts. If this status lasts for a specific

time and the CSP pin voltage rises above the reference voltage (1 V), the latch mode is set. Note that

the latch mode is different from the shutdown status in that the switching operation is stopped but the

internal circuitry operates normally.

To reset the latch operation to protect the IC from short-circuiting, either lower VIN to the timer latch

reset voltage or lower or lower the level of the shutdown pin to “L”. Note that the latch operation is not

reset even if VIN falls below the UVLO voltage.

5. UVLO function

This IC includes a UVLO (under-voltage lockout) circuit to prevent the IC from malfunctioning due to a

transient status when power is applied or a momentary drop of the supply voltage. When UVLO is in

the detection state, switching is stopped and the external FET is held in the off status. Once UVLO

enters the detection state, the soft-start function is reset.

Note that the other internal circuits operate normally and that the status is different from the power-off

status.

S8337 Datasheet(PDF) 13 Page - Seiko Instruments Inc

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