rt9238 ETC-unknow, rt9238 Datasheet - Page 15

• Manufacturer Part Number: rt9238
• Description: Vrm 8.5 Pwm And Triple Linear Power System Controller
• Manufacturer: ETC-unknow

Application Guidelines
Soft-Start Interval
Initially, the soft-start function clamps the error
amplifier’s output of the PWM converter. This
generates PHASE pulses of increasing width that
charge the output capacitor(s). The resulting output
voltages start-up as shown in Fig.3.
The soft-start function controls the output voltage rate
of rise to limit the current surge at start-up. The soft-
start interval and the surge current are programmed
by the soft-start capacitor, C
faster soft-start interval increases the peak surge
current. Using the recommended 0.1µF soft start
capacitors ensure all output voltages ramp up to their
set values in a quick and controlled fashion, while
meeting the system timing requirements.
DS9238-01 July 2001
Notes: 0=connect to GND, 1=open or connect to 3.3V through pull up resistor
VID4
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
VID3
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
SS
. Programming a
VID2
0
0
0
0
0
0
0
1
1
1
1
1
1
1
0
0
0
0
Pin Name
VID1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
1
1
0
0
Preliminary
VID0
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
Shutdown
The PWM output does not switch until the soft-start
voltage (V
voltage. Additionally, the reference on each linear’s
amplifier is clamped to the soft-start voltage. Holding
the SS24 pin low (with an open drain or open
collector signal) turns off regulators 1, 2 and 3.
Regulator 4 (MCH) will simply drop its output to the
intermediate soft-start level. This output is not
allowed to violate the 2V maximum potential gap to
the ATX 3.3V output.
Layout Considerations
MOSFETs switch very fast and efficiently. The speed
with which the current transitions from one device to
another
interconnecting impedances and parasitic circuit
VID25
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0
0
0
0
causes
SS13
) exceeds the oscillator’s valley
Normal OUT1 Voltage
1.525+40mV=1.565
1.550+40mV=1.590
1.575+40mV=1.615
1.600+40mV=1.640
1.625+40mV=1.665
1.650+40mV=1.690
1.675+40mV=1.715
1.700+40mV=1.740
1.725+40mV=1.765
1.750+40mV=1.790
1.775+40mV=1.815
1.800+40mV=1.840
1.825+40mV=1.865
1.850+40mV=1.890
1.900+40mV=1.940
1.950+40mV=1.990
2.000+40mV=2.040
2.050+40mV=2.090
voltage
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