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SI9136

更新时间：2025-06-28 02:25:23
品牌：VISHAY
描述：Multi-Output Power-Supply Controller

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中文翻译

免费 PCB/SMT

SI9136 概述

Multi-Output Power-Supply Controller 多路输出电源控制器

SI9136 数据手册

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Si9136  
Vishay Siliconix  
Multi-Output Power-Supply Controller  
FEATURES  
D Up to 95% Efficiency  
D High Efficiency Pulse Skipping Mode Operation at  
Light Load  
D 3% Total Regulation (Each Controller)  
D 5.5-V to 30-V Input Voltage Range  
D 3.3-V, 5-V, and 12-V Outputs  
D Only Three Inductors Required No Transformer  
D LITTLE FOOTR Optimized Output Drivers  
D Internal Soft-Start  
D 200-kHz Low-Noise Fixed Frequency Operation  
D Precision 3.3-V Reference Output  
D 30 mA Linear Regulator Output  
D Minimal External Control Components  
D 28-Pin SSOP Package  
DESCRIPTION  
The Si9136 is a current-mode PWM and PSM converter  
controller, with two synchronous buck converters (3.3 V and  
5 V) and a flyback (non-isolated buck-boost) converter (12 V).  
Designed for portable devices, it offers a total five power  
outputs (three tightly regulated dc/dc converter outputs, a  
precision 3.3-V reference and a 5-V LDO output). It requires  
minimum external components and is capable of achieving  
conversion efficiencies approaching 95%.  
The Si9136 is available in a 28-pin SSOP package and  
specified to operate over the extended commercial (0_C to  
90_C) temperature range.  
FUNCTIONAL BLOCK DIAGRAM  
V
IN  
5-V  
Linear  
Regulator  
3.3-V  
Voltage  
Reference  
V
REF  
(+3.3 V)  
V
L
(5.0 V)  
3.3-V  
SMPS  
5-V  
SMPS  
+3.3 V  
+5 V  
+12 V  
12-V SMPS  
Control  
Inputs  
Power-Up Control  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
1
Si9136  
Vishay Siliconix  
ABSOLUTE MAXIMUM RATINGS  
V
P
V
to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 to +36 V  
DH3 to LX , DH5 to LX ,  
3 5  
DHFY to LXFY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to (BSTX +0.3 V)  
IN  
to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±2 V  
GND  
a
Continuous Power Dissipation (T = 90_C)  
to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 to +6.5 V  
A
L
b
28-Pin SSOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572 mW  
BST , BST , BSTFY to GND . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +36 V  
3
5
Operating Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . 0_C to 90_C  
Storage Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . –40_C to 125_C  
Lead Temperature (Soldering, 10 Sec.) . . . . . . . . . . . . . . . . . . . . . . . . . 300_C  
V
Short to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous  
L
LX to BST ; LX to BST ; LXFY to BST . . . . . . . . . . . . . . . . . –6.5 V to 0.3 V  
3
3
5
5
Inputs/Outputs to GND  
(CS , CS , CSP, CSN) . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to (V +0.3 V)  
3
5
L
5 ON/OFF, 3 ON/OFF, 12 ON/OFF . . . . . . . . . . . . . . . . . . . . . –0.3 V to +5.5 V  
Notes  
DL3, DL5 to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to (V +0.3 V)  
L
a. Device mounted with all leads soldered or welded to PC board.  
DLFY to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Input of Flyback  
b. Derate 9.52 mW/_C above 90_C.  
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation  
ofthe device at these or any other conditions beyond those indicated in the operational sections ofthespecificationsisnotimplied. Exposuretoabsolutemaximumrating  
conditions for extended periods may affect device reliability.  
SPECIFICATIONS  
Specific Test Conditions  
Limits  
V
= 15 V , I = I  
= 0 mA  
REF  
IN  
VL  
Parameter  
3.3-V Buck Controller  
Mina Typb Maxa  
Unit  
T
A
= 0_C to 90_C, All Converters ON  
Total Regulation (Line, Load, and Temperature)  
Line Regulation  
V
IN  
= 6 to 30 V, 0 < V  
– V < 90 mV  
FB3  
3.23  
90  
3.33  
3.43  
±0.5  
±0.5  
160  
V
CS3  
V
IN  
= 6 to 30 V  
%
Load Regulation  
0 < V  
– V  
< 90 mV  
FB3  
CS3  
Current Limit  
V
CS3  
– V  
125  
50  
mV  
kHz  
_
FB3  
Bandwidth  
L = 10 mH, C = 330 mF  
= 20 mW  
Phase Margin  
R
SENSE  
65  
5-V Buck Controller  
Total Regulation (Line, Load, and Temperature)  
Line Regulation  
V
IN  
= 6 to 30 V, 0 < V  
– V < 90 mV  
FB5  
4.88  
90  
5.03  
5.18  
±0.5  
±0.5  
160  
V
CS5  
V
IN  
= 6 to 30 V  
%
Load Regulation  
0 < V  
– V  
< 90 mV  
FB5  
CS5  
Current Limit  
V
CS5  
– V  
125  
50  
mV  
kHz  
_
FB5  
Bandwidth  
L = 10 mH, C = 330 mF  
= 20 mW  
Phase Margin  
R
SENSE  
65  
12-V Flyback Controller  
Total Regulation (Line, Load, and Temperature)  
Line Regulation  
V
IN  
= 6 to 30 V, 0 < V  
– V < 300 mV  
CSN  
11.4  
330  
12.0  
12.6  
±0.5  
±0.5  
500  
V
CSP  
V
IN  
= 6 to 30 V  
%
Load Regulation  
0 < V  
– V  
< 300 mV  
FBN  
CSP  
Current Limit  
V
CSP  
– V  
410  
10  
mV  
kHz  
_
CSN  
Bandwidth  
L = 10 mH, C = 100 mF  
= 100 mW, C = 120 pF  
Phase Margin  
R
SENSE  
65  
comp  
Internal Regulator  
V
V
V
V
V
Output  
All Converters OFF, V >5.5 V, 0 <I <30 mA  
4.7  
3.6  
5.5  
4.2  
L
L
L
L
IN  
L
V
Fault Lockout Voltage  
Fault Lockout Hysteresis  
/FB5 Switchover Voltage  
/FB5 Switchover Hysteresis  
75  
75  
mV  
V
4.2  
4.7  
mV  
L
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
2
Si9136  
Vishay Siliconix  
SPECIFICATIONS  
Specific Test Conditions  
Limits  
Mina Typb Maxa  
V
IN  
= 15 V , I = I  
= 0 mA  
REF  
VL  
Parameter  
Reference  
Unit  
T
= 0_C to 90_C, All Converters ON  
A
REF Output  
No External Load  
0 to 1 mA  
3.24  
3.30  
30  
3.36  
75  
V
REF Load Regulation  
mV  
Supply Current  
Supply Current*Shutdown  
Supply Current*Operation  
All Converters OFF, No Load  
35  
60  
mA  
All Converters ON, No Load, F  
= 200 kHz  
1100  
1800  
OCS  
Oscillator  
Oscillator Frequency  
Maximum Duty Cycle  
180  
92  
200  
95  
220  
kHz  
%
Outputs  
Gate Driver Sink/Source Current (Buck)  
Gate Driver On-Resistance (Buck)  
DL3, DH3, DL5, DH5 Forced to 2 V  
High or Low  
1
2
A
W
A
7
Gate Driver Sink/Source Current (Flyback)  
Gate Driver On-Resistance (Flyback)  
DHFY, DLFY Forced to 2 V  
High or Low  
0.2  
15  
W
5 ON/OFF, 3 ON/OFF, and 12 ON/OFF  
V
0.8  
IL  
V
V
IH  
2.4  
Notes  
a. The algebraic convention whereby the most negative value is a minimum and the most positive a maximum.  
b. Typical values are for DESIGN AID ONLY, not guaranteed nor subject to production testing.  
PIN CONFIGURATION  
SSOP-28  
1
2
28  
27  
26  
25  
24  
23  
22  
21  
20  
19  
18  
17  
16  
15  
ORDERING INFORMATION  
Part Number  
Temperature Range  
VOUT  
3
Si9136LG  
0 to 90_C  
3.3 V, 5 V, 12 V  
4
5
6
Evaluation Board  
Temperature Range  
Board Type  
7
Si9136DB  
0 to 90_C  
Surface Mount  
8
9
10  
11  
12  
12  
14  
Top View  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
3
Si9136  
Vishay Siliconix  
PIN DESCRIPTION  
Pin  
Number  
Symbol  
Description  
1
CS  
3
Current sense input for 3.3-V buck.  
2
FBFY  
BSTFY  
DHFY  
LXFY  
Feedback for flyback.  
3
Boost capacitor connection for flyback converter.  
Gate-drive output for flyback high-side MOSFET.  
Inductor connection for flyback converter.  
Gate-drive output for flyback low-side MOSFET.  
Current sense positive input for flyback converter.  
Current sense negative input for flyback converter.  
Analog ground.  
4
5
6
DLFY  
7
CSP  
8
CSN  
9
GND  
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
26  
27  
28  
COMP  
REF  
Flyback compensation connection, if required.  
3.3-V internal reference.  
12 ON/OFF  
ON and OFF control input for 12-V flyback controller.  
3.3 ON/OFF ON and OFF control input for 3.3-V buck controller.  
5 ON/OFF  
CS  
ON and OFF control input for 5-V buck controller.  
Current sense input for 5-V buck controller.  
Inductor connection for buck 5-V.  
5
DH5  
LX  
Gate-drive output for 5-V buck high-side MOSFET.  
Boost capacitor connection for 5-V buck converter.  
Gate-drive output for 5-V buck low-side MOSFET.  
Power ground.  
5
BST  
5
DL5  
PGND  
FB  
5
Feedback for 5-V buck.  
V
L
5-V logic supply voltage for internal circuitry.  
Input voltage  
V
IN  
DL3  
BST  
Gate-drive output for 3.3-V buck low-side MOSFET.  
Boost capacitor connection for 3.3-V buck converter.  
Inductor connection for 3.3-V buck low-side MOSFET.  
Gate-drive output for 3.3-V buck high-side MOSFET.  
Feedback for 3.3-V buck.  
3
LX  
3
DH3  
FB  
3
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
4
Si9136  
Vishay Siliconix  
TYPICAL CHARACTERISTICS (_2C5 UNLESS NOTED)  
Efficiency vs. 3.3-V Output Current  
Efficiency vs. 5.0-V Output Current  
100  
90  
100  
90  
Frequency = 200 kHz  
= 6 V  
Frequency = 200 kHz  
V
IN  
15 V  
V
IN  
= 6 V  
15 V  
80  
70  
60  
80  
70  
60  
30 V  
30 V  
3.3 V Off, 12 V Off  
5 V On, 12 V Off  
50  
50  
0.001  
0.01  
0.1  
1
10  
0.001  
0.01  
0.1  
Current (A)  
1
10  
Current (A)  
Efficiency vs. 12-V Output Current  
85  
80  
V
IN  
= 15 V  
Frequency = 200 kHz  
6 V  
75  
70  
65  
30 V  
5 V On, 3.3 V Off  
60  
55  
0.001  
0.01  
Current (A)  
0.1  
1
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
5
Si9136  
Vishay Siliconix  
TYPICAL WAVEFORMS  
5-V Converter (V = 10 V)  
5-V Converter (V = 10 V)  
IN  
IN  
Ch1: V  
Ch1: V  
OUT  
OUT  
Ch2: Load  
Current (1 A/div)  
Ch2: Load  
Current (1 A/div)  
PWM Loading  
PWM Unloading  
5-V Converter (V = 10 V)  
5-V Converter (V = 10 V)  
IN  
IN  
Ch1: V  
OUT  
Ch1: V  
OUT  
Ch2: Load  
Current (1 A/div)  
Ch2: Load  
Current (1 A/div)  
PSM Õ PWM  
PWM Õ PSM  
5-V Converter (V = 10 V)  
IN  
5-V Converter (V = 10 V)  
IN  
Ch2: V  
OUT  
Ch2: V  
OUT  
Ch3: Inductor  
Node  
(L X5)  
Ch3: Inductor  
Node  
(L X5)  
Ch4: Inductor  
Current (1A/div)  
Ch4: Inductor  
Current (1A/div)  
PSM Operation  
PWM Operation  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
6
Si9136  
Vishay Siliconix  
TYPICAL WAVEFORMS  
3-V Converter (V = 10 V)  
3-V Converter (V = 10 V)  
IN  
IN  
Ch1: V  
OUT  
OUT  
ad  
Ch2: Load  
(1 A/div)  
Current (1 A/div)  
PWM, Loading  
PWM, Unloading  
3-V Converter (V = 10 V)  
3-V Converter (V = 10 V)  
IN  
IN  
ad  
(1 A/div)  
oad  
(1 A/div)  
PSM Õ PWM  
PWM Õ PSM  
12-V Converter (V = 10 V)  
Start-Up  
IN  
3.3-V Output  
5-V Output  
Ch1: V  
OUT  
12-V Output  
Inductor Current,  
5-V Converter  
(2 A/div)  
Ch4: Load  
Current  
(100 mA/div)  
250-mA Transient  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
7
Si9136  
Vishay Siliconix  
STANDARD APPLICATION CIRCUIT  
V
IN  
+5 V up to 30 mA  
C7  
33 mF  
D1  
CMPD2836  
CMPD2836  
C5  
D2  
4.7 mF  
C4  
33 mF  
V
IN  
V
L
C1  
0.1 mF  
C2  
0.1 mF  
BST  
BST  
3
5
Q2  
Si4416DY  
L1, 10 mH  
R
7
DH5  
LX  
R
cs1  
Q1  
Si4416DY  
0.02 W  
+5 V  
DH3  
LX  
5
C3  
330 mF  
3
Q4  
Si4812DY  
R
1
L2  
10 mH  
R
cs2  
DL5  
0.02 W  
+3.3 V  
Q3  
Si4812DY  
DL3  
CS  
FB  
5
C6  
330 mF  
5
D3  
CMPD2836  
C8  
CS  
3
C9  
4.7 mF  
BSTFY  
0.1 mF  
Q5  
DHFY  
LXFY  
Si2304DS  
+12 V 0 to  
250 mA  
L3, 10 mH  
D4, D1FS4  
C10  
100 mF  
D5, D1FS4  
FB3  
Q6  
Si2304DS  
DLFY  
CSP  
5 ON/OFF  
R
R
6
cs3  
3.3 ON/OFF  
12 ON/OFF  
CSN  
FBFY  
+3.3 V up  
to 1 mA  
REF  
COMP  
PGND  
GND  
C11  
1 mF  
C12  
120 pF  
FIGURE 1.  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
8
Si9136  
Vishay Siliconix  
TIMING DIAGRAMS  
The converter is enabled  
ON/OFF  
V
IN  
is applied  
V
IN  
LDO is activated  
after V is applied  
IN  
V
L
REF circuit is activated  
after V becomes  
available  
2.4 V  
L
V
REF  
After V  
goes above  
REF  
2.4 V, the converter is  
turned on  
OSC EN  
(Sysmon EN)  
Oscillator is activated  
OSC  
Slow soft-start gradually  
increases the maximum  
inductor current  
4 ms  
f
(SS)  
DH  
max  
High-side gate drive duty  
ratio gradually increases  
to maximum  
t
BBM  
Low-side gate drive  
D
L
FIGURE 2. Converter is Enabled Before V is Applied  
IN  
The converter is  
enabled  
ON/OFF  
V
IN  
is applied  
V
IN  
LDO is activated  
after V is applied  
IN  
V
L
REF circuit is activated  
after V becomes  
available  
L
2.4 V  
V
REF  
After V  
goes above  
REF  
2.4 V, the converter is  
turned on  
OSC EN  
(Sysmon EN)  
Oscillator is activated  
OSC  
4 ms  
Slow soft-start gradually  
increases the maximum  
inductor current  
f
(SS)  
DH  
DL  
max  
FIGURE 3. Converter is Enabled After V is Applied  
IN  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
9
Si9136  
Vishay Siliconix  
TIMING DIAGRAMS  
V
IN  
[ V (V )  
L
V
L
4 V  
3.4 V  
RESET  
V
REF  
OSC EN  
(Sysmon EN)  
OSC  
D
H
D
L
f
(SS)  
max  
FIGURE 4. Power Off Sequence  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
10  
Si9136  
Vishay Siliconix  
DETAIL FUNCTIONAL BLOCK DIAGRAM  
FB  
5
CS_  
FB_  
+
_
1X  
R
R
X
Internal voltage  
divider is only  
used on 5-V  
Error  
output.  
Amplifier  
Y
–
5/3 ON/OFF_  
BST_  
PWMCMP  
+
REF  
–
+
DH  
DH  
Logic  
Control  
Pulse  
Skipping  
Control  
LX_  
SLC  
BBM  
DL  
20 mV  
V
L
Current  
Limit  
DL  
V
Soft-Start  
SYNC  
Rectifier Control  
t
FIGURE 5. Buck Block Diagram  
FBFY  
R1  
ON/OFF  
R2  
Error  
Amplifier  
PWM  
Comparator  
BSTY  
–
+
–
Logic  
Control  
DH  
REF  
+
LXFY  
COMP  
DHFY  
DLFY  
C/S  
Amplifier  
Pulse  
Skipping  
Control  
DL  
ICSP  
ICSN  
–
+
–
+
100 mV  
Current Limit  
V
Soft-Start  
t
FIGURE 6. PWM Flyback Block Diagram  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
11  
Si9136  
Vishay Siliconix  
DETAIL FUNCTIONAL BLOCK DIAGRAM  
5-V  
Linear  
Regulator  
V
IN  
FB  
5
CS  
5
5-V  
Buck  
BST  
5
5 ON/OFF  
3 ON/OFF  
12 ON/OFF  
Controller  
DH5  
LX  
5
V
L
4.5 V  
DL5  
4 V  
FB  
3
CS  
3
Logic  
3.3-V  
Buck  
Controller  
Control  
BST  
3.3-V  
3
Reference  
DH3  
LX  
2.4 V  
3
DL3  
FYBFY  
ICSP  
12-V  
Flyback  
Controller  
ICSN  
BSTFY  
DHFY  
LXFY  
DLFY  
FIGURE 7. Complete Si9136 Block Diagram  
DESCRIPTION OF OPERATION  
Start-up Sequence  
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  
converterdelivering 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 VL is supplied by the 5-V converter output.  
Si9136’s outputs are controlled by three specific input control  
lines; 3.3 ON/OFF, 5 ON/OFF, and 12 ON/OFF. Once VIN is  
applied, the VL, the 5-V LDO will come up within its tolerance.  
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-mA of supply current.  
Buck Converter Operation:  
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-startperiod  
(approximately 4 ms), preventing excessive currents from  
being drawn from the input.  
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.  
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  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
12  
Si9136  
Vishay Siliconix  
DESCRIPTION OF OPERATION (CONT'D)  
Normal Operation: Buck Converters  
called for brevity a flyback. It consists of two n-channel  
MOSFET switches that are turned on and off in phase, and two  
diodes. Similar to the buck converter, during the light load  
conditions, the flyback converter will switch at a frequency  
lower than the internal clock frequency, which can be defined  
as pulse skipping mode (PSM); otherwise, it is operating in  
normal PWM mode.  
In normal operation, the buck converter high-side MOSFET is  
turned on with a delay (known as break-before-make time -  
tBBM), after the rising edge of the clock. After a certain on time,  
the high-side MOSFET is turned off and then after a delay  
(tBBM), the low-side MOSFET is turned on until the next rising  
edge of the clock, or the inductor current reaches zero. The  
tBBM (approximately 25 ns to 60 ns), has been optimized to  
guarantee the efficiency is not adversely affected at the high  
switching frequency and a specified minimum to account for  
variations of possible MOSFET gate capacitances.  
Normal Operation: Flyback Converter  
In normal operation mode, the two MOSFETs are turned on at  
the rising edge of the clock, and then turned off. The on time is  
controlled internally to provide excellent load, line, and  
temperature regulation. The flyback converter has load, line  
and temperature regulation well within 0.5%.  
During the normal operation, the high-side MOSFET switch  
on-time is controlled internally to provide excellent line and  
load regulation over temperature. Both buck converters  
should have load, line, regulation to within 0.5% tolerance.  
Pulse Skipping: Flyback Converter  
Pulse Skipping: Buck Converters  
Under the light load conditions, similar to the buck converter,  
the flyback converter will enter pulse skipping mode. The  
MOSFETs will be turned on until the inductor current increases  
tosuchalevelthatthevoltageacrossthepinCSPandpinCSN  
reaches 100 mV, or the on time reaches the maximum duty  
cycle. After the MOSFETs are turned off, the inductor current  
will conduct through two diodes until it reaches zero. At this  
point, the flyback converter output will rise slightly above the  
regulation level, and the converter will stay idle for one or  
several clock cycle(s) until the output falls back slightly below  
the regulation level. The switching losses are reduced by  
skipping pulses and so the efficiency during light load is  
preserved.  
When the buck converter switching frequency is less than the  
internalclock frequency, itsoperationmodeisdefinedaspulse  
skipping mode. During this mode, the high-side MOSFET is  
turnedon until VCS-VFB reaches 20 mV, ortheontimereaches  
its maximum duty ratio. After the high-side MOSFET is turned  
off, the low-side MOSFET is turned on after the tBBM delay,  
which will remain on until the inductor current reaches zero.  
The output voltage will rise slightly above the regulation  
voltage after this sequence, causing the controller to stay idle  
for the next one, or several clock cycles. When the output  
voltage falls slightly below the regulation level, the high-side  
MOSFET will be turned on again at the next clock cycle. With  
the converter remaining idle during some clock cycles, the  
switching losses are reduced in order to preserve conversion  
efficiency during the light output current condition.  
Current Limit: Flyback Converter  
Current Limit: Buck Converters  
Similartothebuckconverter;whenthevoltageacrosspinCSP  
and pin CSN exceeds 410-mV typical, the two MOSFETs will  
be turned off regardless of the input and output conditions.  
When the buck converter inductor current is too high, the  
voltage across pin CS3(5) and pin FB3(5) exceeds  
approximately 120 mV, the high-side MOSFET would be  
turned off instantaneously regardless of the input, or output  
condition. The Si9136 features clock cycle by clock cycle  
current limiting capability.  
Flyback Lowside Drive  
Unlike the gate drive for the two buck converters, the flyback  
lowside gate drive DLFY is powered by a voltage that can be  
as high as 15 V with 20-V input for the flyback converter. If this  
poses concerns on the MOSFET VGS rating, a simple  
resistor-zener circuit can be used: a resistor series with gate  
and zener diode across the gate and source to clamp its  
voltage. A 100-W, 10-V combination works well.  
Flyback Converter Operation:  
Designed mainly for PCMCIA or EEPROM programming, the  
Si9136 has a 12-V output non-isolated buck boost converter,  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
13  
Si9136  
Vishay Siliconix  
DESCRIPTION OF OPERATION (CONT'D)  
Grounding:  
efficiency. The converters are current mode control, with a  
bandwidthsubstantially higher than the LC tank dominant pole  
frequency of the output filter. To ensure stability, the minimum  
capacitance and maximum ESR values are:  
There are two separate grounds on the Si9136, analog signal  
ground (GND) and power ground (PGND). The purpose of two  
separate grounds is to prevent the high currents on the power  
devices (both external and internal) from interfering with the  
analog signals. The internal components of Si9136 have their  
grounds tied (internally) together. These two grounds are then  
tied together (externally) at a single point, to ensure Si9136  
noise immunity.  
VREF  
VOUT x Rcs  
CLOAD  
w
ESR v  
2p xĂ VOUT x RCS x BW  
VREF  
Where VREF = 3.3 V, VOUT is the output voltage (5 V or 3.3 V),  
Rcs is the current sensing resistor in ohms and BW = 50 khz  
This separation of grounds should be maintained in the  
external circuitry, with the power ground of all power devices  
being returned directly to the input capacitors, and the small  
signal ground being returned to the GND pin of Si9136.  
With the components specified in the application circuit  
(L = 10 mH, RCS = 0.02 W,  
COUT = 330 mF,  
ESR  
ON/OFF Function  
approximately 0.1 W), the converter should have a bandwidth  
at approximately 50 kHz, with minimum phase margin of 65_,  
and dc gain above 50 dB.  
Logic-low shuts off the appropriate section by disabling the  
gate drive stage. High-side and low-side gate drivers are  
turned off when ON/OFF pins are logic-low. Logic-high  
enables the DH and DL pins.  
Other Outputs  
The Si9136 also provides a 3.3-V reference which can be  
external loaded up to 1 mA, aswellas, a5-VLDOoutputwhich  
can be loaded 30 mA, or even more depending on the system  
application. When the 5-V buck converter is turned on, the 5-V  
LDOoutputisshortedwiththe5-Vbuckconverteroutput, soits  
loading capability is substantially increased. For stability, the  
3.3-V reference output requires a 1-mF capacitor, and 5-V LDO  
output requires a 4.7-mF capacitor.  
Stability:  
Buck Converters:  
In order to simplify designs, the Si9136 requires no specified  
external components except load capacitors for stability  
control. Meanwhile, it achieves excellent regulation and  
Document Number: 70818  
S-00583—Rev. C, 03-Apr-00  
www.vishay.com S FaxBack 408-970-5600  
14  

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