BD9109FVM-LB Datasheet, PDF (5/23 Pages) Rohm – Synchronous Buck Converter Integrated FET

BD9109FVM-LB
Description of Block – continued
・Soft-start function
EN terminal shifted to “High” activates a soft-starter to gradually establish the output voltage with the current limited
during startup, by which it is possible to prevent an overshoot of output voltage and an inrush current.
・Shutdown function
With EN terminal shifted to “Low”, the device turns to Standby Mode, and all the function blocks including reference
voltage circuit, internal oscillator and drivers are turned to OFF. Circuit current during standby is 0 μA (Typ).
・UVLO function
Detects whether the input voltage sufficient to secure the output voltage of this IC is supplied. And the hysteresis width of
50 to 300 mV (Typ) is provided to prevent output chattering.
Hysteresis 50 to 300mV
VCC
EN
VOUT
Standby mode
Tss
Soft start
Operating mode
Tss
Tss
Standby
mode
Operating mode
Standby
mode
Operating mode
Standby mode
*Soft Start time(typ)
Tss
UVLO
UVLO
EN
Figure 9 . Soft start, Shutdown, UVLO timing chart
BD9109FVM-LB
Unit
1
msec
UVLO
・Short-current protection circuit with time delay function
Turns OFF the output to protect the IC from breakdown when the incorporated current limiter is activated continuously for the
fixed time(TLATCH) or more. The output thus held tuned OFF may be recovered by restarting EN or by re-unlocking UVLO.
EN
VOUT
Limit
IL
Standby
mode
Output OFF
latch
Operating mode
TLATCH
Standby
mode
Operating mode
*Timer Latch time (typ) ^EN
Timer latch
EN
Figure 10 . Short-current protection circuit with time delay timing char
BD9109FVM-LB Unit
TLATCH
2
msec
In addition to current limit circuit, output short detect circuit is built in on BD9109FVM-LB. If output voltage fall below
2V(typ, BD9109FVM-LB) output voltage will hold turned OFF.
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21.Feb.2014 Rev.002