BD9111NV_14 Datasheet, PDF (9/25 Pages) Rohm – Synchronous Buck Converter with Integrated FET

BD9111NV
Datasheet
2. Description of Operations
(1) Soft-Start Function
During start-up, the soft-start circuit gradually establishes the output voltage to limit the input current. This prevents the
overshoot in the output voltage and inrush current.
(2) Shutdown Function
When the EN terminal is “low”, the device operates in Standby Mode and all functional blocks, including reference
voltage circuit, internal oscillator and drivers, are turned OFF. Circuit current during standby is 0μA (Typ).
(3) UVLO Function
The UVLO circuit detects whether the supplied input voltage is sufficient to obtain the output voltage of this IC. The
UVLO threshold, which has a hysteresis of 100mV (Typ), prevents output bouncing.
Hysteresis 100mV
VCC
EN
VOUT
Standby Mode
tss
Soft Start
Operating Mode
tss
tss
Standby
Mode
Operating Mode
Standby
Mode
Operating Mode
Standby Mode
UVLO
UVLO
EN
Figure 22. Soft Start, Shutdown, UVLO Timing Chart
UVLO
(4) Short-Circuit Protection Circuit with Time Delay Function
To protect the IC from breakdown, the short-circuit protection circuit turns the output OFF when the internal current
limiter is activated continuously for a fixed time (tLATCH) or more. The output that is kept off may be turned on again by
restarting EN or by resetting UVLO.
EN
Output Short circuit
Threshold Voltage
VOUT
IL Limit
IL
Output OFF
Latch
Output OFF
t1<tLATCH
Operating Mode
t2=tLATCH
Output OFF
Operating Mode
EN
Timer Latch
EN
Figure 23. Short-Circuit Current Protection Circuit with Time Delay Timing Chart
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02.Oct.2014 Rev.002