SI9130 Datasheet, PDF (9/13 Pages) Vishay Siliconix – Pin-Programmable Dual Controller-Portable PCs

Si9130
Vishay Siliconix
3.3-V Switching Supply
The 3.3-V supply is regulated by a current-mode PWM
controller in conjunction with several externals: two n-channel
MOSFETs, a rectifier, an inductor and output capacitors (see
Figure 1). The gate drive supplied by DH₃ needs to be greater
than V_L , so it is provided by the bootstrap circuit consisting of
a 100-nF capacitor and diode connected to BST3.
A low-side switching MOSFET connected to DL₃ increases
efficiency by reducing the voltage across the rectifier diode. A
low value sense resistor in series with the inductor sets the
maximum current limit, to disallow current overloads at
power-on or in short-circuit situations.
at power-on are avoided, and power-supplies can be
sequenced with different turn-on delay times by selecting the
correct capacitor value.
5-V Switching Supply
The 5-V supply is regulated by a current-mode PWM controller
which is nearly the same as the 3.3-V output. The dropout
voltage across the 5-V supply, as shown in the schematic in
Figure 1, is 400 mV (typ) at 2 A. If the voltage at V+ falls, nearing
5 V, the 5-V supply will lower as well, until the V_L linear regulator
output falls below the 4-V undervoltage lockout threshold.
Below this threshold, the 5-V controller is shut off.
The soft-start feature on the Si9130 is capacitor
programmable; pin SS₃ functions as a constant current source
to the external capacitor connected to GND. Excess currents
The frequency of both PWM controllers is set at 300 kHz when
the SYNC pin is tied to REF. Connecting SYNC to either GND
or V_L sets the frequency at 200 kHz.
V+
V_L
3.45ADJ
3.6ADJ
REF
SHDN
+5-V LDO
Linear
Regulator
+3.3-V
Reference
ON
4V
4.5 V
SYNC
2.8 V
300 kHz/200 kHz
Oscillator
ON
STANDBY
3.3-V
PWM
Controller
(See Figure 3)
ON
5-V
PWM
Controller
(See Figure 3)
ON
FB₃
CS₃
BST₃
DH₃
LX₃
DL₃
SS₃
PGND
ON₃
FB₅
CS₅
BST₅
DH₅
LX₅
DL₅
SS₅
Document Number: 70190
S-40805—Rev. F, 26-Apr-04
FIGURE 2. Si9130 Block Diagram
ON₅
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