SI9136DB Vishay, SI9136DB Datasheet - Page 12

• Manufacturer Part Number: SI9136DB
• Description: Pulse Width Modulation (PWM) Controller IC
• Manufacturer: Vishay

Specifications of SI9136DB

• Silicon Manufacturer: Vishay
• Application Sub Type: Power Supply Controller
• Kit Application Type: Power Management
• Silicon Core Number: SI9136
• Kit Contents: Board
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Si9136
Vishay Siliconix
Start-up Sequence
Si9136’s outputs are controlled by three specific input control
lines; 3.3 ON/OFF, 5 ON/OFF, and 12 ON/OFF. Once V
applied, the V
When any one of these control lines becomes logic high, the
precision 3.3-V reference will also come up. Immediately
afterwards, the oscillator will begin and the corresponding
converter will come up with its own tolerance. In the event of all
three converters are turned off, the oscillator and the reference
output will be turned off, and the total system will only draw
35- A of supply current.
Each converter can soft-start independently. This internal
soft-start circuitry for each converter will gradually increases
the inductor maximum peak current during the soft-start period
(approximately 4 ms), preventing excessive currents from
being drawn from the input.
Si9136 converts a 5.5-V to 30-V input voltage to five different
output voltages; two buck (step-down) high current, PWM,
switch-mode supplies of 3.3-V and 5-V, one “flyback” PWM
switch-mode supply of 12-V, one precision 3.3-V reference
www.vishay.com FaxBack 408-970-5600
12
V
V
IN
L
L
, the 5-V LDO will come up within its tolerance.
Reference
Regulator
Linear
3.3-V
5-V
2.4 V
4 V
FIGURE 7. Complete Si9136 Block Diagram
IN
is
Control
Logic
and one 5-V low drop out (LDO) linear regulator output.
Switch-mode supply output current capabilities depend on
external components (can be selected to exceed 10 A). In the
standard application circuit illustrated in Figure 1, each buck
converter is capable of delivering 5 A, with the flyback
converter delivering 250 mA. The recommended load currents
for the precision 3.3-V reference output is less than 1 mA, and
the 5-V LDO output is less than 30 mA. In order to maximize
power efficiency of the converter, when the 5-V buck converter
output (FB5) voltage is above 4.5-V, the internal 5-V LDO is
turned off and V
Buck Converter Operation:
The 3.3-V and 5-V buck converters are both current-mode
PWM and PSM (during light load operation) regulators using
high-side bootstrap n-channel and low-side n-channel
MOSFETs. At light load conditions, the converters switch at a
lower frequency than the clock frequency, seen like some
clock pulses between the actual switching are skipped, this
operating condition is defined as pulse-skipping. The
operation of the converter(s) switching at clock frequency is
defined as normal operation.
4.5 V
12 ON/OFF
5 ON/OFF
3 ON/OFF
L
is supplied by the 5-V converter output.
Controller
Controller
Controller
Flyback
3.3-V
Buck
Buck
12-V
5-V
S-00583—Rev. C, 03-Apr-00
Document Number: 70818
FB
CS
BST
DH5
LX
DL5
FB
CS
BST
DH3
LX
DL3
FYBFY
ICSP
ICSN
BSTFY
DHFY
LXFY
DLFY
5
5
3
3
5
3
5
3