BD95513MUV_10 Datasheet, PDF (10/18 Pages) Rohm – Switching Regulator with MOS FET for DDR-SDRAM Cores

BD95513MUV
Technical Note
●Operation
The BD95513MUV is a switching regulator incorporating ROHM’s proprietary H³Reg^TM CONTROLLA control system.
When V_OUT drops suddenly due to changes in load, the system quickly restores the output voltage by extending the t_on time
interval. This improves the regulator’s transient response. When light-load mode is activated, the IC employs the Simple
Light Load Mode (SLLM^TM) controller, further improving system efficiency.
H³Reg^TM Control
(Normal Operation)
VFB
VREF
HG
When V_FB falls below the reference voltage (0.7V),
the H³Reg^TM CONTROLLA is activated;
tON =
VREF
1
VIN ^× f ^{[sec]・・・(1)}
High gate output is determined by the above formula.
LG
(Rapid Changes in Load)
VFB
VREF
Io
HG
LG
tON+α
When V_OUT drops due to a sudden change in load and the
voltage remains below V_REF after the preprogrammed t_ON time
interval has elapsed, the system quickly restores V_OUT by
extending the t_ON time, thereby improving transient response.
Light Load Control
(SLLM^TM Mode)
VFB
VREF
HG
LG
0A
(QLLM Mode)
VFB
VREF
HG
LG
0A
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SLLM^TM mode is enabled by setting the MODE pin to logic high.
When the low gate is off and the current through the inductor is 0
(current flowing from V_OUT to SW), the SLLM^TM function is
activated, disabling high gate output.
If V_FB falls below V_REF again, the high gate is switched back on,
lowering the switching frequency of the regulator and yielding
higher efficiency when powering light loads.
QLLM mode is enabled by setting the MODE pin to HiZ or
middle voltage. When the lower gate is off and the current
through the inductor is 0 (current flowing from V_OUT to SW),
QLLM mode is activated, disabling high gate output.
If V_FB falls below V_REF within a programmed time interval
(typ. 40 µs), the high gate is switched on, but if V_FB does not fall
below V_REF, the lower gate is forced on, dropping V_FB and
switching the high gate back on.
The minimum switching frequency is set to 25 kHz (T = 40 µs),
which keeps the regulator’s frequency from entering the audible
spectrum but yields less efficient results than SLLM^TM mode.
10/17
2010.10- Rev.A