SI9130DB Vishay, SI9130DB Datasheet - Page 9

• Manufacturer Part Number: SI9130DB
• Description: Pulse Width Modulation (PWM) Controller IC
• Manufacturer: Vishay

Specifications of SI9130DB

• Silicon Manufacturer: Vishay
• Application Sub Type: Pin-programmable Controller
• Kit Application Type: Power Management
• Silicon Core Number: SI9130
• Kit Contents: Board
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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 DH
than V
a 100-nF capacitor and diode connected to BST3.
A low-side switching MOSFET connected to DL
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.
The
programmable; pin SS
to the external capacitor connected to GND. Excess currents
Document Number: 70190
S-40805—Rev. F, 26-Apr-04
L
soft-start
, so it is provided by the bootstrap circuit consisting of
3.45ADJ
3.6ADJ
SHDN
SYNC
REF
V+
V
feature
L
3
functions as a constant current source
on
300 kHz/200 kHz
+5-V LDO
Reference
ON
Regulator
Oscillator
the
+3.3-V
Linear
2.8 V
4 V
Si9130
3
needs to be greater
ON
FIGURE 2. Si9130 Block Diagram
is
STANDBY
3
increases
capacitor
4.5 V
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
output falls below the 4-V undervoltage lockout threshold.
Below this threshold, the 5-V controller is shut off.
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.
(See Figure 3)
(See Figure 3)
Controller
Controller
3.3-V
PWM
PWM
ON
ON
5-V
FB
CS
BST
DH
LX
DL
SS
PGND
ON
FB
CS
BST
DH
LX
DL
SS
ON
Vishay Siliconix
3
5
3
3
3
5
5
5
3
5
3
5
3
5
3
5
L
linear regulator
www.vishay.com
Si9130
9