End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
500-kHz Half-Bridge DC/DC Controller
with Integrated Secondary Synchronous Rectification Drivers
DESCRIPTION
FEATURES
Si9122A is a half-bridge controller IC ideally suited to fixed
telecom applications where high efficiency is required at low
output voltages (e.g. < 3.3 V). Designed to operate within the
fixed telecom voltage range of 33 V to 75 V and withstand
100 V, 100 ms transients, the IC is capable of controlling and
driving both the low and high-side switching devices of a half
bridge circuit and also controlling the switching devices on
the secondary side of the bridge. Due to the very low onresistance of the secondary MOSFETs, a significant
increase in conversion efficiency can be achieved as
compared with conventional Schottky diodes. Control of the
secondary devices is by means of a pulse transformer and a
pair of inverters. Such a system has efficiencies well in
excess of 90 % even for low output voltages. On-chip control
of the dead time delays between the primary and secondary
synchronous signals keep efficiencies high and prevent
accidental destruction of the power transformer. An external
resistor sets the switching frequency from 200 kHz to
625 kHz.
Si9122A has advanced current monitoring and control
circuitry which allow the user to set the maximum current in
the primary circuit. Such a feature acts as protection against
output shorting and also provides constant current into large
capacitive loads during start-up or when paralleling power
supplies. Current sensing is by means of a sense resistor on
the low-side primary device.
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28 V to 75 V input voltage range
Compatible with ETSI 300 132-2
Integrated ± 1 A half-bridge primary drivers
RoHS
COMPLIANT
Secondary synchronous rectifier control
signals with programmable deadtime delay
Voltage mode control
Voltage feedforward compensation
High voltage pre-regulator operates during start-up
Current sensing on low-side primary device
Frequency foldback eliminates constant current tail
Advanced maximum current control during start-up and
shorted load
Low input voltage detection
Programmable soft-start function
Over temperature protection
APPLICATIONS
• Network cards
• Power supply modules
FUNCTIONAL BLOCK DIAGRAM
VCC
REG_COMP
VIN
28 V to 75 V
BST
Synchronous
Rectifiers
DH
LX
Si9122A
1 V to 12 V Typ.
+
VOUT
–
DL
CS2
VIN_DET
CS1
SRH
CL_CONT
VCC
PGND
GND
BBM
ROSC
VREF
SS
SRL
Error
Amplifier
+
-
EP
VREF
Opto Isolator
Figure 1.
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
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End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
TECHNICAL DESCRIPTION
Si9122A is a voltage mode controller for the half-bridge
topology. With 100 V depletion mode MOSFET capability,
the Si9122A is capable of powering directly from the high
voltage bus to VCC through an external PNP pass transistor,
or may be powered through an external regulator directly
through the VCC pin. With PWM control, Si9122A provides
peak efficiency throughout the entire line and load range. In
order to simplify the design of efficient secondary
synchronous rectification circuitry, Si9122A provides
intelligent gate drive signals to control the secondary
MOSFETs. With independent gate drive signals from the
controller, transformer design is no longer limited by the gate
to source rating of the secondary-side MOSFETs. Si9122A
provides constant VGS voltage, independent of line voltage
to minimize the gate charge loss as well as conduction loss.
A break-before-make function is included to prevent shoot
through current or transformer shorting. Adjustable BreakBefore-Make time is incorporated into the IC and is
programmable by an external resistor value.
Si9122A is packaged in lead (Pb)-free TSSOP-20 and
MLP65-20 packages. To satisfy stringent ambient
temperature requirements, Si9122A is rated to handle the
industrial temperature range of - 40 °C to 85 °C. When a
situation arises which results in a rapid increase in primary
(or secondary current) such as output shorted or start-up
with a large output capacitor, control of the PWM generator
is handed over to the current loop. Monitoring of the load
current is by means of an external current sense resistor in
the source of the primary low-side switch.
SI9122 BLOCK DIAGRAM
VIN
REG_COMP
VCC
Pre-Regulator
VREF
ROSC
9.1 V
+
-
High-Side
Primary
Driver
VUVLO
BST
DH
Int
8.8 V
LX
VINDET
VREF
+
-
VUV
+
-
VSD
Low-Side
Driver
VFF
VCC
DL
OSC
Ramp
132 kΩ
550 mV
60 kΩ
EP
+
Error Amplifier
+
PWM
Comparator
V REF
20 µA
SS
PGND
2
CS1
SRH
SYNC
Driver High
ISS
OTP
8V
CS2
VCC
Driver
Control
and
Timing
VCC
+
-
Peak DET
SRL
Duty Cycle
Control
Si9122
Over Current Protection
GND
CL_CONT
SYNC
Driver Low
BBM
Figure 2.
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Document Number: 73492
S-80038-Rev. D, 14-Jan-08
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
ABSOLUTE MAXIMUM RATINGS All voltages referenced to GND = 0 V
Parameter
Limit
VIN (Continuous)
VIN (100 ms)
100
VCC
14.5
VBST
Continuous
95
100 ms
113.2
VLX
100
VBST - VLX
15
VREF, ROSC
- 0.3 to VCC + 0.3
Logic Inputs
- 0.3 to VCC + 0.3
Analog Inputs
- 0.3 to VCC + 0.3
HV Pre-Regulator Input Current (Continuous)
5
Storage Temperature
- 65 to 150
Operating Junction Temperature
Power Dissipationa
Thermal Impedance (JA)
Unit
80
150
TSSOP-20b
V
mA
°C
MLP65-20c
850
2500
mW
TSSOP-20
MLP65-20
75
38
°C/W
Notes:
a. Device Mounted on JEDEC compliant 1S2P test board.
b. Derate - 14 mW/°C above 25 °C.
c. Derate - 26 mW/°C above 25 °C.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation
of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect device reliability.
RECOMMENDED OPERATING RANGE All voltages referenced to GND = 0 V
Parameter
VIN
VCC Operating
Limit
28 to 75
10.5 to 13.2
Unit
V
CVCC
4.7
µF
fOSC
200 to 625
kHz
ROSC
22.6 to 72
RBBM
22 to 50
CREF
0.1
CBOOST
0.1
Analog Inputs
0 V to VCC - 2 V
Digital Inputs
0 V to VCC
Reference Voltage Output Current
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
0 to 2.5
k
µF
V
mA
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Si9122A
Vishay Siliconix
SPECIFICATIONSa
Limits
- 40 to 85 °C
Symbol
Test Conditions
Unless Otherwise Specified
fNOM = 500 kHz, VIN = 75 V
VINDET = 7.5 V; 10.5 V VCC 13.2 V
Min.b
Typ.c
Output Voltage
VREF
VCC = 12 V, 25 °C Load = 0 mA
3.2
3.3
Short Circuit Current
ISREF
VREF = 0 V
Load Regulation
dVr/dir
IREF = 0 to - 2.5 mA
- 30
Power Supply Rejection
PSRR
at 100 Hz
60
Parameter
Max.b
Unit
Reference (3.3 V)
3.4
V
- 50
mA
- 75
mV
dB
Oscillator
ROSC = 30 k, fNOM = 500 kHz
- 20
Max Frequencyh
Accuracy (1 % ROSC)
FMAX
ROSC = 22.6 k
500
Foldback Frequencyd
FFOBK
fNOM = 500 kHz, VCS2 - VCS1 > 150 mV
IBIAS
VEP = 0 V
20
625
750
100
%
kHz
Error Amplifier
Input Bias Current
- 40
- 15
µA
Gain
AV
- 2.2
V/V
Bandwidth
BW
5
MHz
Power Supply Rejection
Slew Rate
PSRR
at 100 Hz
SR
60
dB
0.5
V/µs
± 150
mV
Current Sense Amplifier
VCS1 - GND, VCS2 - GND
Input Voltage CM Range
VCM
Input Amplifier Gain
AVOL
17.5
dB
Input Amplifier Bandwidth
BW
5
MHz
Input Amplifier Offset Voltage
VOS
±5
mV
dVCS = 0
120
ICL_CONT
dVCS = 100 mV
0
dVCS = 170 mV
>2
Lower Current Limit Threshold
VTLCL
IPD = IPU - ICL_CONT = 0
See Figure 6
100
Upper Current Limit Threshold
VTHCL
IPD > 2 mA
150
IPU < 500 µA
- 50
CL_CONT Current
Hysteresis
CL_CONT Clamp Level
CL_CONT(min)
IPU = 500 µA
0.6
µA
mA
mV
1.5
V
PWM Operation
DMAX
Duty
Cyclee
DMIN
fOSC = 500 kHz
VEP = 0 V
90
VEP = 1.75 V
92
95
%
< 15
VCS2 - VCS1 > 150 mV
3
Pre-Regulator
Input Voltage
+ VIN
IIN = 10 µA
Input Leakage Current
ILKG
VIN = 75 V, VCC > VREG
IREG1
VIN = 75 V, VINDET < VSD
86
200
IREG2
VIN = 75 V, VINDET > VREF
8
14
Regulator Bias Current
Regulator_Comp
Pre-Regulator Drive Capacility
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ISOURCE
ISINK
ISTART
VCC = 12 V
VCC < VREG
28
75
10
- 29
- 19
-9
50
82
110
20
V
µA
mA
µA
mA
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
SPECIFICATIONSa
Parameter
Symbol
Test Conditions
Unless Otherwise Specified
fNOM = 500 kHz, VIN = 75 V
VINDET = 7.5 V; 10.5 V VCC 13.2 V
Limits
- 40 to 85 °C
Min.b
Typ.c
Max.b
7.4
9.1
10.4
9.1
9.7
Unit
Pre-Regulator
VCC Pre-Regulator Turn Off
Threshold Voltage
VREG1
Undervoltage Lockout
VUVLO
VUVLO Hysteresis
g
VREG2
VINDET > VREF
TA = 25 °C
8.5
VINDET = 0 V
VCC Rising
9.2
TA = 25 °C
7.15
8.8
9.8
8.1
8.8
9.3
VUVLOHYS
V
0.5
Soft-Start
Soft-Start Current Output
Soft-Start Completion Voltage
ISS
Start-Up Condition
12
20
28
µA
VSS_COMP
Normal Operation
7.35
8.05
8.85
V
VSD
VINDET Rising
350
550
720
Shutdown
VINDET Shutdown
VSD Hysteresis
VINDET
200
mV
VINDET Input Threshold Voltages
VINDET - VIN Under Voltage
VUV
VUV Hysteresis
VINDET Rising
3.13
3.3
3.46
VINDET
0.23
0.3
0.35
V
Over Temperature Protection
Activating Temperature
TJ Increasing
160
De-Activating Temperature
TJ Decreasing
130
°C
Converter Supply Current (VCC)
Shutdown
ICC1
Shutdown, VINDET = 0 V
50
Switching Disabled
ICC2
VINDET < VREF
4
8
12
Switching w/o Load
ICC3
VINDET > VREF, fNOM = 500 kHz
5
10
15
ICC4
VCC = 12 V, CDH = CDL = 3 nF
CSRH = CSRL = 0.3 nF
Switching with CLOAD
350
µA
mA
21
Output MOSFET DH Driver (High-Side)
VBST - 0.3
Output High Voltage
VOH
Sourcing 10 mA
Output Low Voltage
VOL
Sinking 10 mA
Boost Current
IBST
VLX = 75 V, VBST = VLX + VCC
1.3
1.9
2.7
LX Current
ILX
VLX = 75 V, VBST = VLX + VCC
- 1.3
- 0.7
- 0.4
- 1.0
- 0.75
Peak Output Source
Peak Output Sink
ISOURCE
ISINK
Rise Time
tr
Fall Time
tf
VCC = 10.5 V
VLX + 0.3
0.75
1.0
35
CDH = 3 nF
V
mA
A
ns
35
Output MOSFET DL Driver (Low-Side)
Output High Voltage
VOH
Sourcing 10 mA
Output Low Voltage
VOL
Sinking 10 mA
Peak Output Source
ISOURCE
Peak Output Sink
ISINK
Rise Time
tr
Fall Time
tf
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
VCC = 10.5 V
CDL = 3 nF
VCC - 0.3
0.3
- 1.0
0.75
1.0
35
35
- 0.75
V
A
ns
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Si9122A
Vishay Siliconix
SPECIFICATIONSa
Parameter
Symbol
Limits
- 40 to 85 °C
Test Conditions
Unless Otherwise Specified
fNOM = 500 kHz, VIN = 75 V
VINDET = 7.5 V; 10.5 V VCC 13.2 V
Min.b
VCC - 0.4
Typ.c
Max.b
Unit
Synchronous Rectifier (SRH, SRL) Drivers
Output High Voltage
VOH
Sourcing 10 mA
Output Low Voltage
VOL
Sinking 10 mA
tBBM1
Break-Before-Make Timef
tBBM2
tBBM3
tBBM4
Peak Output Source
Peak Output Sink
ISOURCE
ISINK
Rise Time
tr
Fall Time
tf
TA = 25 °C, RBBM = 33 k, See Figure 3
TA = 25 °C, RBBM = 33 k, LX = 75 V
VCC = 10.5 V
CSRH = CSRL = 0.3 nF
0.4
V
55
40
35
ns
55
- 100
100
35
35
mA
ns
Voltage Mode
Error Amplifier
td1DH
Input to High-Side Switch Off
< 200
td2DL
Input to Low-Side Switch Off
< 200
td3DH
Input to High-Side Switch Off
< 200
td4DL
Input to Low-Side Switch Off
< 200
ns
Current Mode
Current Amplifier
ns
Notes:
a. Refer to PROCESS OPTION FLOWCHART for additional information.
b. The algebraic convention whereby the most negative value is a minimum and the most positive a maximum (- 40 °C to 85 °C).
c. Typical values are for DESIGN AID ONLY, not guaranteed nor subject to production testing.
d. FMIN when VCL_CONT at clamp level. Typical foldback frequency change + 20 %, - 30 % over temperature.
e. Measured on SRL or SRH outputs.
f. See figure 3 for Break-Before-Make time definition.
g. VUVLO tracks VREG1 by a diode drop.
h. Guaranteed by design and characterization, not tested in production.
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Document Number: 73492
S-80038-Rev. D, 14-Jan-08
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
TIMING DIAGRAM FOR MOS DRIVERS
VCC
PWM
PWM
PWM
PWM
GND
VCC
DL
DL
SRL
SRL
GND
VCC
GND
VBST
DH
DH
VMID
DH
DH
GND
VCC
SRH
SRH
GND
Time
tBBM1
tBBM2
tBBM3
DH
tBBM4
BST = LX + VCC
50 %
V LX
LX
DH, LX
DH, LX
VMID
VCC
SRH
50 %
DH, LX
GND
tBBM3
DL
tBBM4
SRL
SRL
VCC
GND
Return to: Specification Table
Rectification Timing Sequence
tBBM1
tBBM2
Primary MOSFET Drivers
Secondary MOSFET Drivers
Figure 3.
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
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Si9122A
Vishay Siliconix
PIN CONFIGURATION
Si9122ADQ (TSSOP-20)
VIN
1
20
BST
REG_COMP
2
19
DH
VCC
3
18
LX
VREF
4
17
DL
16
PGND
15
SRH
VCC
14
SRL
13
GND
5
ROSC
6
EP
7
VINDET
8
CS1
9
CS2
12
10
11
Si9122ADLP (MLP65-20)
1
20
2
19
3
18
DH
4
17
LX
VREF
5
16
DL
SS
GND
6
15
PGND
7
14
BBM
ROSC
8
13
9
12
SRL
10
11
SS
VIN
REG_COMP
EP
CL_CONT
VINDET
CS1
Top View
BST
SRH
BBM
CS2
CL_CONT
Top View
ORDERING INFORMATION
Part Number
Temperature Range
Si9122ADQ-T1-E3
Package
TSSOP-20
- 40 °C to 85 °C
Si9122ADLP-T1-E3
Eval Board
Contact Factory
MLP65-20
Temperature Range
- 10 °C to 70 °C
Board Type
Surface Mount and Thru-Hole
PIN DESCRIPTION
Pin Number
Name
1
VIN
2
REG_COMP
Function
Input supply voltage for the start-up circuit
Control signal for an external pass transistor
3
VCC
Supply voltage for internal circuitry
4
VREF
3.3 V reference
5
GND
Ground
6
ROSC
External resistor connection to oscillator
7
EP
8
VINDET
Voltage control input
VIN under voltage detect and shutdown function input. Shuts down or disables switching when VINDET
falls below preset threshold voltages and provides the feed forward voltage.
9
CS1
Current limit amplifier negative input
10
CS2
Current limit amplifier positive input
11
CL_CONT
12
BBM
Current limit compensation
Programmable break-before-make time connection to an external resistor to set time delay
13
SS
Soft-start control - external capacitor connection
14
SRL
Signal transformer drive, sequenced with the primary side
15
SRH
16
PGND
17
DL
Low-side gate drive signal - primary
18
LX
High-side source and transformer connection node
19
DH
20
BST
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Signal transformer drive, sequenced with the primary side
Power ground.
High-side gate drive signal - primary
Bootstrap voltage to drive the high-side N-Channel MOSFET switch
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
VCC
VIN
12 V
+
-
Bandgap
Reference
3.3 V
VREF
9.1 V
VREG
9.1 V
+
-
VINDET
Voltage
Feedforward
VUVLO
+
-
VUV
VREF
CL_CONT
8.8 V
BST
160 C Temp
Protection
550 mV
VSD
OSC
Oscillator
High Voltage
Interface
DH
LX
VUV VUVLO
OTP
Clock
Clock
VCC
Logic
Low-Side
Driver
132 kΩ
DL
60 kΩ
EP
+
–
+
VREF/2
Current
Control
CS2
CS1
Logic
PGND
PWM
Generator
Gain
Timer
VCC
Loop
Control
+
100 mV
Blanking
VCC
CL_CONT
GND
VCC
8V
High-Side
Primary
Driver
VSD
+
-
Frequency
Foldback
ROSC
Pre-Regulator
BBM
Synchronous
Driver
(Low)
SRL
Si9122A
20 µA
SS
Synchronous
Driver
(High)
SRH
Soft-Start
SS Enable
Figure 4. Detailed Si9122A Block Diagram
DETAILED OPERATION
Start-Up
When VINEXT rises above 0 V, the internal pre-regulator
begins to charge up the VCC capacitor. Current into the
external VCC capacitor is limited to typically 40 mA by the
internal DMOS device. When VCC exceeds the UVLO
voltage of 8.8 V a soft-start cycle of the switch mode supply
is initiated. The VCC supply continues to be charged by the
pre-regulator until VCC equals VREG. During this period,
between VUVLO and VREG, excessive load current will result
in VCC falling below VUVLO and stopping switch mode
operation. This situation is avoided by the hysteresis
between VREG and VUVLO and correct sizing of the VCC
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
capacitor, bootstrap capacitor and the soft-start capacitor.
The value of the VCC capacitor should therefore be chosen
to be capable of maintaining switch mode operation until the
required VCC current can be supplied from the external circuit
(e.g via a power transformer winding and zener regulator).
Feedback from the output of the switch mode supply charges
VCC above VREG and fully disconnects the pre-regulator,
isolating VCC from VIN. VCC is then maintained above VREG
for the duration of switch mode operation. In the event of an
over voltage condition on VCC, an internal voltage clamp
turns on at 14.5 V to shunt excessive current to GND.
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Care needs to be taken if there is a delay prior to the external
circuit feeding back to the VCC supply. To prevent excessive
power dissipation within the IC it is advisable to use an
external PNP device. A pin has been incorporated on the IC,
(REG_COMP) to provide compensation when employing the
external device. In this case the VIN pin is connected to the
base of the PNP device and controls the current, while the
REG_COMP pin determines the frequency compensation of
the circuit. The value of the REG_COMP capacitor cannot be
too big, otherwise it will slow down the response of the
pre-regulator in the case that fault situations occur and
pre-regulator needs to be turned on again. To understand
the operation please refer to Figure 5.
The soft-start circuit is designed for the dc-dc converter to
start-up in an orderly manner and reduce component stress
on the IC. This feature is programmable by selecting an
external CSS. An internal 20 µA current source charges CSS
from 0 V to the final clamped voltage of 8 V. In the event of
UVLO or shutdown, VSS will be held low (< 1 V) disabling
driver switching. To prevent oscillations, a longer soft-start
time may be needed for highly capacitive loads and/or high
peak output current applications.
Reference
The reference voltage of Si9122A is set at 3.3 V. The
reference voltage should be de-coupled externally with
0.1 µF capacitor. The VREF voltage is 0 V in shutdown mode
and has 50 mA source capability.
Voltage Mode PWM Operation
Under normal load conditions, the IC operates in voltage
mode and generates a fixed frequency pulse width
modulated signal to the drivers. Duty cycle is controlled over
a wide range to maintain output voltage under line and load
variation. Voltage feed forward is also included to take
account of variations in supply voltage VIN.
In the half-bridge topology requiring isolation between output
and input, the reference voltage and error amplifier must be
supplied externally, usually on the secondary side. The error
information is thus passed to the power controller through an
opto-coupling device. This information is inverted, hence 0 V
represents the maximum duty cycle, whilst 2 V represents
minimum duty cycle. The error information enters the IC via
pin EP, and is passed to the PWM generator via an inverting
amplifier. The relationship between duty cycle and VEP is
shown in the typical characteristic Graph, duty cycle vs.
VEP 25 °C , page 11. Voltage feedforward is implemented by
taking the attenuated VIN signal at VINDET and directly
modulating the duty cycle.
At start-up, i.e., once VCC is greater than VUVLO, switching is
initiated under soft-start control which increases primary
switch on-times linearly from DMIN to DMAX over the soft-start
period. Start-up from a VINDET power down is also initiated
under soft-start control.
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Half-Bridge and Synchronous Rectification Timing
Sequence
The PWM signal generated within the Si9122A controls the
low and high-side bridge drivers on alternative cycles. A
period of inactivity always results after initiation of the softstart cycle until the soft-start voltage reaches approximately
1.2 V and PWM controlled switching begins. The first bridge
driver to switch is always the low-side (DL), as this allows
charging of the high-side boost capacitor.
The timing and coordination of the drives to the primary and
secondary stages is very important and shown in figure 3. It
is essential to avoid the situation where both of the
secondary MOSFETs are on when either the high or the lowside switch are active. In this situation the transformer would
effectively be presented with a short across the output. To
avoid this, a dedicated break-before-make circuit is included
which will generate non overlapping waveforms for the
primary and the secondary drive signals. This is achieved by
a programmable timer which delays the switching on of the
primary driver relative to the switching off of the related
secondary and subsequently delays the switching on of the
secondary relative to the switching off of the related primary.
Typical variations of BBM times with respect to RBBM and
other operating parameters are shown on page 13 and 14.
Primary High- and Low-Side MOSFET Drivers
The drive voltage for the low-side MOSFET switch is
provided directly from VCC. The high-side MOSFET however
requires the gate voltage to be enhanced above VIN. This is
achieved by bootstrapping the VCC voltage onto the LX
voltage (the high-side MOSFET source). In order to provide
the bootstrapping an external diode and capacitor are
required as shown on the application schematic. The
capacitor will charge up after the low-side driver has turned
on. The switch gate drive signals DH and DL are shown in
figure 3.
Secondary MOSFET Drivers
The secondary side MOSFETs are driven from the Si9122A
via a center tapped pulse transformer and inverter drivers.
The waveforms from SRH and SRL are shown in figure 3. Of
importance is the relative voltage between SRH and SRL,
i.e. that which is presented across the primary of the pulse
transformer. When both potentials of SRL and SRH are
equal then by the action of the inverting drivers both
secondary MOSFETs are turned on.
Oscillator
The oscillator is designed to operate at a nominal frequency
of 500 kHz. The 500 kHz operating frequency allows the
converter to minimize the inductor and capacitor size,
improving the power density of the converter. The oscillator
and therefore the switching frequency is programmable by
attaching a resistor to the ROSC pin. Under overload
conditions the oscillator frequency is reduced by the current
overload protection to enable a constant current to be
maintained into a low impedance circuit.
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
Current Limit
VIN Voltage Monitor - VINDET
Current mode control providing constant current operation is
achieved by monitoring the differential voltage VCS between
the CS1 and CS2 pins, which are connected to a current
sense resistor on the primary low-side MOSFET. In the
absence of an overcurrent condition, VCS is less than lower
current limit threshold VTLCL (typical 100 mV); CL_CONT is
pulled up linearly via the 120 µA current source (IPU) and
both DL and DH switch at half the oscillator set frequency.
When a moderate overcurrent condition occurs (VTLCL < VCS
< VTHCL), the CL_CONT capacitor will be discharged at a rate
that is proportional to VCS - 100 mV by the IPD current
source. Both driver outputs are in frequency fold-back mode
and the switching frequency becomes roughly 20 % of
normal switching frequency. When a severe overcurrent
condition occurs (VTHCL < VCS), the NMOS discharges
CL_CONT capacitor immediately at 2 mA rate and the
CL_CONT voltage will be clamped to 1.2 V disabling both DL
and DH outputs.
The chip provides a means of sensing the voltage of VIN, and
withholding operation of the output drivers until a minimum
voltage of VREF (3.3 V, 300 mV hysteresis), is achieved. This
is achieved by choosing an appropriate resistive tap between
the ground and VIN, and comparing this voltage with the
reference voltage. When the applied voltage is greater than
VREF, the output drivers are activated as normal. VINDET also
provides the input to the voltage feed forward function.
However, if the divided voltage applied to the VINDET pin is
greater than VCC - 0.3 V, the high-side driver, DH, will stop
switching until the voltage drops below VCC - 0.3 V. Thus, the
resistive tap on the VIN divider must be set to accommodate
the normal VCC operating voltage to avoid this condition.
Alternatively, a zener clamp diode from VINDET to GND may
also be used.
Shutdown Mode
If VINDET is forced below the lower VSD threshold, the device
will enter SHUTDOWN mode. This powers down all
unnecessary functions of the controller, ensures that the
primary switches are off, and results in a low level current
demand from the VIN or VCC supplies.
Before VCS reaches severe overcurrent condition, a lowering
of the CL_CONT voltage results in PWM control of the output
drive being taken over by the current limit control loop
through CL_CONT. Current control initially reduces the
switching duty cycle toward the minimum the chip can reach
(DMIN). If this duty cycle reduction still cannot lower the load
current, then the switching frequency will start to fold back to
minimum 1/5 of the nominal frequency. This prevents the
on-time of the primary drivers from being reduced to below
100 ns and avoids current tails. If VCS > VTHCL, the switching
will then stop.
VINEXT
REXT
VIN
12 V
(Si9122A)
PNP Ext
Auxillary
VCC
HVDMOS
With constant current mode control and frequency foldback
protection of the MOSFET switches is increased. The
converter reverts to voltage mode operation immediately
when the primary current falls below the limit level, and
CL_CONT capacitor is charged up and clamped to 6.5 V. The
soft-start function does not apply during current limit period,
as this would constitute hiccup mode operation.
VCC
REG_COMP
CEXT
2 nF
14.5 V
VREF
CVCC
0.5 µF
GND
Figure 5. High-Voltage Pre-Regulator Circuit
VCC
AV
+
Peak Detect
OSC
IPU
120 µA (nom)
GM
VOFFSET
-
CL_CLAMP
CL_CONT
CS1
CS2
-
AV
+
AV
150 mV
REXT
Blank
+
GM
AV
IPD
0 to 240 µA (nom)
CEXT
100 mV
Figure 6 . Current Limit Circuit
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
www.vishay.com
11
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
TYPICAL CHARACTERISTICS
600
3.300
3.295
500
V REF (V)
FOSC (kHz)
3.290
400
3.285
3.280
300
3.275
200
20
30
40
50
60
70
3.270
- 50
80
- 25
0
25
75
Temperature (°C)
fOSC vs. ROSC at VCC = 12 V
VREF vs. Temperature, VCC = 12 V
100
100
10.0
90
3.6 V = VINDET
80
Duty Cycle (%)
9.5
V REG(V)
50
ROSC (kΩ)
9.0
VINDET > VREF
TC = - 11 mV/C
8.5
4.8 V
70
60
7.2 V
50
40
VCC = 12 V
30
20
8.0
10
7.5
- 50
- 25
0
25
50
75
100
125
0
0.0
150
0.5
1.0
Temperature ( C)
2.0
SRL, SRH Duty Cycle vs. VEP
VREG vs. Temperature, VIN = 48 V
8.20
25
VCC = 13 V
8.15
23
TC = + 1.25 mV/C
8.10
VCC = 12 V
21
V SS (V)
I SS1 (µA)
1.5
VEP (V)
VINDET > VREF
8.05
19
8.00
VCC = 10 V
17
15
- 50
7.95
- 25
0
25
50
75
Temperature (°C)
ISS vs. Temperature
www.vishay.com
12
100
125
7.90
- 50
- 25
0
25
50
75
100
125
150
Temperature (°C)
VSS vs. Temperature, VCC = 12 V
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
11
13
10
12
9
11
ICC3 (mA)
IREG2 (mA)
TYPICAL CHARACTERISTICS
8
10
7
9
6
8
5
- 50
- 25
0
25
50
75
7
- 50
100
- 25
0
75
100
250
250
VCC = 12 V
200
VCC = 12 V
200
150
ISINK (mA)
ISOURCE (mA)
50
ICC3 vs. Temperature
IREG2 vs. Temperature
100
150
100
50
50
0
0
0
200
400
600
0
800
200
400
600
VOH (mV)
VOL (mV)
DH, DL ISOURCE vs. VOH
DH, DL ISINK vs. VOL
35
800
35
30
30
VCC = 12 V
VCC = 12 V
25
25
ISINK (mA)
ISOURCE (mA)
25
Temperature (°C)
Temperature (°C)
20
15
20
15
10
10
5
5
0
0
0
200
400
600
800
0
200
400
600
VOH (mV)
VOL (mV)
SRL, SRH ISOURCE vs. VOH
SRL, SRH ISINK vs. VOL
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
800
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13
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
TYPICAL CHARACTERISTICS
65
100
VCC = 12 V
90
tBBM4
VCC = 12 V
tBBM1
tBBM1
55
80
tBBM4
tBBM2
60
tBBM3
tBBM2
50
45
tBBM (ns)
tBBM (ns)
70
tBBM3
35
40
25
30
15
20
25
30
35
40
25
45
30
35
40
45
RBBM (kΩ)
RBBM (kΩ)
tBBM vs. RBBM, VEP = 0 V
tBBM vs. RBBM, VEP = 1.65 V
60
80
VEP = 1.65 V
RBBM = 33 kΩ
tBBM1, VCC = 13 V
tBBM1, VCC = 12 V
tBBM1, VCC = 10 V
55
70
50
tBBM1, 2 (ns)
tBBM1, 2 (ns)
tBBM1, VCC = 10 V
60
VEP = 0 V
RBBM = 33 kΩ
50
tBBM1, VCC = 12 V
40
tBBM2, VCC = 10 V
tBBM2, VCC = 12 V
40
tBBM1, VCC = 13 V
45
tBBM2, VCC = 10 V
tBBM2, VCC = 12 V
35
tBBM2, VCC = 13 V
tBBM2, VCC = 13 V
30
- 50
- 25
0
25
50
75
100
30
- 50
125
0
25
50
75
100
125
Temperature (°C)
Temperature (°C)
tBBM1, 2 vs. Temperature, VEP = 1.65 V
tBBM1, 2 vs. Temperature, VEP = 0 V
80
70
65
- 25
VEP = 1.65 V
RBBM = 33 kΩ
tBBM4, VCC = 10 V
VEP = 0 V
RBBM = 33 kΩ
tBBM4, VCC = 13 V
70
60
tBBM4, VCC = 12 V
55
tBBM13, 4 (ns)
tBBM13, 4 (ns)
60
tBBM4, VCC = 13 V
50
45
tBBM3, VCC = 13 V
tBBM4, VCC = 12 V
tBBM4, VCC = 10 V
50
tBBM3, VCC = 12 V
40
tBBM3, VCC = 10 V
tBBM3, VCC = 12 V
40
30
35
30
- 50
www.vishay.com
14
tBBM3, VCC = 13 V
tBBM3, VCC = 10 V
- 25
0
25
50
75
100
125
20
- 50
- 25
0
25
50
75
100
Temperature (°C)
Temperature (°C)
tBBM3, 4 vs. Temperature, VEP = 0 V
tBBM3, 4 vs. Temperature, VEP = 1.65 V
125
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
TYPICAL CHARACTERISTICS
80
55
tBBM1, VCC = 13 V
tBBM1, VCC = 12 V
tBBM1, VCC = 10 V
50
tBBM1, 2 (ns)
tBBM1, 2 (ns)
70
tBBM1, VCC = 13 V
60
VEP = 0 V
50
tBBM2, VCC = 10 V
tBBM2, VCC = 12 V
4.5
tBBM1, VCC = 10 V
45
VEP = 1.65 V
tBBM2, VCC = 12 V
40
40
30
3.5
tBBM1, VCC = 12 V
tBBM2, VCC = 13 V
tBBM2, VCC = 13 V
5.5
6.5
35
3.5
7.5
tBBM2, VCC = 10 V
4.5
5.5
VINDET (V)
6.5
7.5
VINDET (V)
tBBM1, 2 vs. VCC vs. VINDET
tBBM1, 2 vs. VCC vs. VINDET
65
80
VEP = 0 V
tBBM4, VCC = 10 V
60
tBBM4, VCC = 12 V
70
tBBM4, VCC = 12 V
tBBM4, VCC = 10 V
55
tBBM13, 4 (ns)
tBBM13, 4 (ns)
tBBM4, VCC = 13 V
60
tBBM4, VCC = 13 V
50
tBBM3, VCC = 10 V
tBBM3, VCC = 12 V
50
45
40
40
35
30
3.5
tBBM3, VCC = 13 V
4.5
5.5
6.5
30
3.5
7.5
VEP = 1.65 V
tBBM3, VCC = 12 V
tBBM3, VCC = 13 V
tBBM3, VCC = 10 V
4.5
5.5
6.5
7.5
VINDET (V)
VINDET (V)
tBBM3, 4 vs. VCC vs. VINDET
tBBM3, 4 vs. VCC vs. VINDET
500
50
500
60
400
D%
300
30
200
20
IOUT
100
10
VOUT
0
0.0
0
0.2
0.4
0.6
0.8
RLOAD (Ω)
IOUT vs. RLOAD (VIN = 72 V)
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
1.0
45
Frequency
400
40
D%
35
30
300
DDL
25
DSRL
200
20
Frequency (kHz)
40
Frequency (kHz)
I OUT, Duty Cycle %. V OUT
50
VROSC (V), FOSC (kH3), Duty Cycle (%)
Frequency
15
100
10
VROSC
5
0
0
1
2
3
4
5
VCLCONT (V)
VROSC, FOSC, and Duty Cycle vs. VCLCONT
www.vishay.com
15
End of Life. Last Available Purchase Date is 31-Dec-2014
Si9122A
Vishay Siliconix
TYPICAL WAVEFORMS
SRL 10 V/div
SRL 10 V/div
IOUT 5 A /div
IOUT 5 A /div
DL 10 V/div
DL 5 V/div
CS2 5 V/div
CS2 50 mV/div
2 µs/div
2 µs/div
Figure 8. Normal Mode, RL = 0.1
Figure 7. Foldback Mode, RL = 0.02
VCL 2 V/div
VIN 2 V/div
VEP 2 V/div
IOUT 10 A/div
VOUT 2 V/div
VCC 2 V/div
200 µs/div
2 ms/div
Figure 10. Overload Recovery
Figure 9. VCC Ramp-Up
DH 5 V/div
LX 20 V/div
SRL 5 V/div
DL 5 V/div
SRH 2 V/div
SRH 5 V/div
SRL 2 V/div
500 ns/div
Figure 11. Effective BBM - Measured On Secondary
500 ns/div
Figure 12. Drive Waveforms
Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon
Technology and Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and
reliability data, see http://www.vishay.com/ppg?73492.
www.vishay.com
16
Document Number: 73492
S-80038-Rev. D, 14-Jan-08
Package Information
Vishay Siliconix
TSSOP: 20-LEAD (POWER IC ONLY)
B
D
4X
N
0.20 C A−B
D
0.20 H A−B
D
2X N/2 TIPS
E1
E
bbb
1.00
b
M
C
A−B
A2
E/2
D
9
0.05
C
A
1 2 3
1.00 DIA.
aaa
H
A1
e
1.00
C
C
SEATING
PLANE
A
D
(14_)
SIDE VIEW
MILLIMETERS
0.25
PARTING
LINE
+
+
H
L
(∝)
6
c
1.00
B
B
(14_)
DETAIL ‘A’
(SCALE: 30/1)
(VIEW ROTATED 90_ C.W.)
C
L
e/2
X
X = A and B
LEAD SIDES
TOP VIEW
Document Number: 72818
28-Jan-04
SEE
DETAIL ‘A’
Dim
A
A1
A2
aaa
b
b1
bbb
c
c1
D
E
E1
e
L
N
P
P1
∝
Min
Nom
Max
—
—
1.10
0.05
—
0.15
0.85
0.90
0.95
0.076
0.19
−
0.30
0.19
0.22
0.25
0.10
0.09
0.09
−
0.20
0.127
0.16
6.50 BSC
6.40 BSC
4.30
4.40
4.50
0.65 BSC
0.50
0.60
0.70
20
4.2
3.0
0_
—
8_
ECN: S-40082—Rev. A, 02-Feb-04
DWG: 5923
END VIEW
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1
Package Information
Vishay Siliconix
-B-
PowerPAKr MLP65-18/20 (POWER IC ONLY)
D
D/2
NXb
Index Area
D/2 E/2
-A-
bbb
M
A
B
C
NXb
2x
E/2
E2/2
E2
2.00
aaa
C
E
Index Area
D/2 E/2
aaa
NXL
2x
C
Detail D
D2/2
D2
TOP VIEW
BOTTOM VIEW
A
//
ccc
C
0.08
C
A3
SEATING
NX
PLANE
-C-
SIDE VIEW
A1
# IDENTIFIER TYPE A
Chamber
e/2
Terminal Tip
e
Terminal Tip
e
5
EVEN TERMINAL SIDE
5
ODD TERMINAL SIDE
DETAIL B
Document Number: 73182
15-Oct-04
www.vishay.com
1
Package Information
Vishay Siliconix
PowerPAK MLP65-18/20 (POWER IC ONLY)
N = 18/20 PITCH: 0.5 mm, BODY SIZE: 6.00 x 5.00
MILLIMETERS*
Dim
Min
Nom
A
0.80
0.90
A1
0.00
0.02
A2
0.00
0.65
A3
0.20 REF
aaa
−
0.15
b
0.18
0.25
bbb
−
0.10
C’
−
0.225
ccc
−
0.10
D
6.00 BSC
D2
4.00
4.15
E
5.00 BSC
E2
3.00
3.15
e
−
0.50
L
0.45
0.55
N
18, 20
ND(18)
9
NE(18)
0
ND(20)
10
NE(20)
0
* Use millimeters as the primary measurement.
INCHES
Max
Min
Nom
Max
Notes
1.00
0.05
1.00
0.031
0.000
0.000
0.039
0.002
0.004
1, 2
1, 2
1, 2
−
0.30
−
−
−
−
0.007
−
−
−
4.25
0.157
3.25
−
0.65
0.118
−
0.018
0.035
0.001
0.003
0.008 REF
0.006
0.010
0.004
0.009
0.004
0.236 BSC
1.63
0.197 BSC
0.124
0.020
0.022
18, 20
9
0
10
0
−
0.012
−
−
−
0.167
0.128
−
0.026
8
4, 10
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2
ECN: S-41946—Rev. A, 18-Oct-04
DWG: 5939
NOTES:
1.
Dimensioning and tolerancing conform to ASME Y14.5M-1994.
2.
All dimensions are in millimeters. All angels are in degrees.
3.
N is the total number of terminals.
4.
The terminal #1 identifier and terminal numbering convention shall conform to JEDEC publication 95 SSP-022. Details of terminal #1 identifier are optional,
but must be located within the zone indicated. A dot can be marked on the top side by pin 1 to indicate orientation.
5.
ND and NE refer to the number of terminals on the D and E side respectively.
6.
Depopulation is possible in a symmetrical fashion.
7.
NJR refers to NON JEDEC REGISTERED.
8.
Dimension “b” applies to metalized terminal and is measured between 0.15 mm and 0.30 mm from the terminal tip. If the terminal has optional radius on
the other end of the terminal, the dimension “b” should not be measured in that radius area.
9.
Coplanarity applies to the exposed heat slug as well as the terminal.
10.
The 45_ chamfer dimension C’ is located by pin 1 on the bottom side of the package.
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Document Number: 73182
15-Oct-04
Legal Disclaimer Notice
www.vishay.com
Vishay
Disclaimer
ALL PRODUCT, PRODUCT SPECIFICATIONS AND DATA ARE SUBJECT TO CHANGE WITHOUT NOTICE TO IMPROVE
RELIABILITY, FUNCTION OR DESIGN OR OTHERWISE.
Vishay Intertechnology, Inc., its affiliates, agents, and employees, and all persons acting on its or their behalf (collectively,
“Vishay”), disclaim any and all liability for any errors, inaccuracies or incompleteness contained in any datasheet or in any other
disclosure relating to any product.
Vishay makes no warranty, representation or guarantee regarding the suitability of the products for any particular purpose or
the continuing production of any product. To the maximum extent permitted by applicable law, Vishay disclaims (i) any and all
liability arising out of the application or use of any product, (ii) any and all liability, including without limitation special,
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Statements regarding the suitability of products for certain types of applications are based on Vishay's knowledge of typical
requirements that are often placed on Vishay products in generic applications. Such statements are not binding statements
about the suitability of products for a particular application. It is the customer's responsibility to validate that a particular product
with the properties described in the product specification is suitable for use in a particular application. Parameters provided in
datasheets and / or specifications may vary in different applications and performance may vary over time. All operating
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Product specifications do not expand or otherwise modify Vishay's terms and conditions of purchase, including but not limited
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Customers using or selling Vishay products not expressly indicated for use in such applications do so at their own risk. Please
contact authorized Vishay personnel to obtain written terms and conditions regarding products designed for such applications.
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