BD9134MUV_14 Datasheet, PDF (9/25 Pages) Rohm – Synchronous Buck Converter with Integrated FET

BD9134MUV
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, such as 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 50mV (Typ) to prevent output chattering.
Hysteresis 50mV
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 Diagram
UVLO
(4) Short-Circuit Protection with Time Delay Function
To protect the IC from breakdown, the short-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
VOUT
Limit
1msec
Output Current in non-control
1/2VOUT
Until output voltage goes up the half of Vo or over,
timer latch is not operated.
(No timer latch, only limit to the output current)
Output voltage OFF Latch
IL
Output Current in control by limit value
(With fall of the output voltage, limit value goes down)
Standby mode
EN
Operated mode
Standby mode
Operated mode
Timer Latch
EN
Figure 23. Short-Circuit Protection with Time Delay Diagram
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03.Oct.2014 Rev.002