MIC5022BWM [MICREL]
Half-Bridge MOSFET Driver; 半桥MOSFET驱动器
| 型号： | MIC5022BWM |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | Half-Bridge MOSFET Driver |
| 文件： | 总9页 (文件大小：133K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC5022
Half-Bridge MOSFET Driver
General Description
Features
The MIC5022 half-bridge MOSFET driver is designed to
operate at frequencies up to 100kHz (5kHz PWM for 2% to
100% duty cycle) and is an ideal choice for high speed
applications such as motor control and SMPS (switch mode
power supplies).
• 12V to 36V operation
• 600ns rise time into 1000pF (high side)
• TTL compatible input with internal pull-down resistor
• Outputs interlocked to prevent cross conduction
• TTL compatible enable
• Fault output indication
• Individual overcurrent limits
• Gate protection
• Internal charge pump (high-side)
• Current source drive scheme reduces EMI
A rising or falling edge on the input results in a current source
pulse or sink pulse on the gate outputs. This output current
pulse can turn on a 2000pF MOSFET in approximately 1µs.
The MIC5022 then supplies a limited current (< 2mA), if
necessary, to maintain the output states.
Applications
• Motor control
• Switch-mode power supplies
Two overcurrent comparators with nominal trip voltages of
50mV make the MIC5022 ideal for use with current sensing
MOSFETs. Externallowvalueresistorsmaybeusedinstead
of sensing MOSFETs for more precise overcurrent control.
Optional external capacitors placed on the C and C pins
TH
TL
may be used to individually control the current shutdown duty
cycles from approximately 20% to <1%. Duty cycles from
20% to about 75% are possible with individual pull-up resis-
tors from C and C to V . An open collector output
Ordering Information
TL
TH
DD
provides a fault indication when either sense input is tripped.
Part Number
MIC5022BWM
MIC5022BN
Temperature Range
–40°C to +85°C
Package
The MIC5022 is available in 16-pin wide SOIC and 14-pin
plastic DIP packages.
16-pin Wide SOIC
14-pin Plastic DIP
–40°C to +85°C
Other members of the MIC502x family include the MIC5020
low-side driver and the MIC5021 high-side driver.
Typical Application
+12V to +36V
MIC5022
1
2
3
4
5
6
7
14
13
12
11
10
9
VDD
VBOOST
Gate H
10µF
TTL Input
Input
2.7nF
M
(PWM signal)
Fault Sense H–
CTH Sense H+
Enable Gate L
CTL Sense L–
Gnd Sense L+
RS1
CTH
CTL
RS2
8
DC Motor Control Application
MIC5022
178
September 1999
MIC5022
Micrel
Pin Configuration
1 VDD
VBOOST 14
Gate H 13
1
2
3
4
5
6
7
8
VDD
NC
NC 16
VBOOST 15
Gate H 14
2 Input
3 Fault Sense H– 12
Input
4 CTH
Sense H+ 11
Gate L 10
Fault Sense H– 13
CTH Sense H+ 12
Enable Gate L 11
5 Enable
6 CTL
Sense L– 9
Sense L+ 8
7 Gnd
CTL
Sense L– 10
Gnd Sense L+ 9
DIP Package
(N)
SOIC Package
(WM)
Pin Description
DIP Pin No.
SOIC Pin No.
Pin Name
VDD
Pin Function
Supply: +12V to +36V. Decouple with ≥ 10µF capacitor.
1
2
1
3
Input
TTL Compatible Input: Logic high turns the high-side external MOSFET on
and the low-side external MOSFET off. Logic low turns the high-side
external MOSFET off and the low-side external MOSFET on. An internal
pull-down returns an open pin to logic low.
3
4
4
5
Fault
CTH
When either sense voltage exceeds threshold, open collector output is open
circuit for 5µs (tG(ON)), then pulled low for tG(OFF). tG(OFF) is adjustable from
CT.
Retry Trimming Capacitor, High Side: Controls the off time (tG(OFF)) of the
overcurrent retry cycle. (Duty cycle adjustment.)
• Open = approx. 20% duty cycle.
• Capacitor to Ground = approx. 20% to < 1% duty cycle.
• Pullup resistor = approx. 20% to approx. 75% duty cycle.
• Ground = maintained shutdown upon overcurrent condition.
5
6
Enable
Output Enable: Disables operation of the output drivers; active high. An
internal pull-down returns an open pin to logic low.
6
7
8
7
8
8
CTL
Gnd
Retry Trimming Capacitor, Low Side: Same function as CTH
Circuit Ground
.
Sense L +
Current Sense Comparator (+) Input, Low Side: Connect to source of low-
side MOSFET. A built-in offset (nominal 50mV) in conjunction with RSENSE
sets the load overcurrent trip point.
9
10
11
Sense L –
Gate L
Current Sense Comparator (–) Input, Low Side: Connect to the negative
side of the low-side sense resistor.
10
Gate Drive, Low Side: Drives the gate of an external power MOSFET. Also
limits VGS to 15V max. to prevent Gate to Source damage. Will sink and
source current.
11
12
Sense H +
Current Sense Comparator (+) Input, High Side: Connect to source of high-
side MOSFET. A built-in offset (nominal 50mV) in conjunction with RSENSE
sets the load overcurrent trip point.
12
13
13
14
Source H –
Gate H
Current Sense Comparator (–) Input, High Side: Connect to the negative
side of the high-side sense resistor.
Gate Drive, High Side: Drives the gate of an external power MOSFET. Also
limits VGS to 15V max. to prevent Gate to Source damage. Will sink and
source current.
14
15
VBOOST
Charge Pump Boost Capacitor: A bootstrap capacitor from VBOOST to the
MOSFET source pin supplies charge to quickly enhance the external
MOSFET’s gate .
September 1999
179
MIC5022
MIC5022
Micrel
Block Diagram
6V Internal Regulator
I1
Fault
CTH
VDD
CINT
2I1
Normal
CHARGE
PUMP
VBOOST
Sense H+
Sense H–
Q1
1.4V
50mV
15V
ON
OFF
Input
6V
↑
↓
ONE-
SHOT
10I2
I2
Gate H
6V
I1
Fault
CTL
CINT
2I1
Normal
Fault
Sense L+
Sense L–
Q1
50mV
VDD
15V
ON
OFF
1.4V
6V
↑
↓
ONE-
SHOT
10I2
I2
Gate L
Enable
Transistor Count: 188
Absolute Maximum Ratings
Operating Ratings
Supply Voltage (V ) ..................................................+40V
Supply Voltage (V ) .................................... +12V to +36V
DD
DD
Input Voltage .................................................. –0.5V to 15V
Sense Differential Voltage..........................................±6.5V
Sense + or Sense – to Gnd.......................... –0.5V to +36V
Fault Voltage ...............................................................+36V
Current into Fault ....................................................... 50mA
Temperature Range
SOIC ...................................................... –40°C to +85°C
PDIP ....................................................... –40°C to +85°C
Timer Voltage (C ) .....................................................+5.5V
T
V
Capacitor .................................................... 0.01µF
BOOST
MIC5022
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September 1999
MIC5022
Micrel
Electrical Characteristics
TA = 25°C, Gnd = 0V, VDD = 12V, Gate CL = 1500pF (IRF540 MOSFET) unless otherwise specificed
Symbol
Parameter
Condition
Min
Typ
2.5
6.0
2.4
3.0
1.4
0.1
20
Max
5
Units
mA
mA
mA
mA
V
D.C. Supply Current
VDD = 12V, Input = 0V
VDD = 36V, Input = 0V
VDD = 12V, Input = 5V
VDD = 36V, Input = 5V
10
5
25
2.0
Input Threshold
0.8
Input Hysteresis
V
Input Pull-Down Current
Enable Threshold
Enable Hysteresis
Input = 5V
10
40
µA
V
0.8
1.4
0.1
0.15
2.0
V
Fault Output
Fault Current = 1.6mA
0.4
V
Saturation Voltage
Note 1
Fault Output Leakage
Fault = 36V
–1
30
30
16
46
10
14
2
0.01
50
+1
70
70
21
52
µA
mV
mV
V
Current Limit Thresh., Low-Side
Current Limit Thresh., High-Side
Gate On Voltage, High-Side
Note 2
Note 2
50
VDD = 12V, Note 3
18
VDD = 36V, Note 3
49
V
Gate On Voltage, Low-Side
VDD = 12V, Note 3
11
V
VDD = 36V, Note 3
15
18
10
V
tG(ON)
tG(OFF)
tDLH
tR
Gate On Time, Fixed
Sense Differential > 70mV
5
µs
µs
µs
µs
µs
µs
µs
µs
µs
µs
Gate Off Time, Adjustable
Gate Turn-On Delay, High-Side
Gate Rise Time, High-Side
Gate Turn-Off Delay, High-Side
Gate Fall Time, High-Side
Gate Turn-On Delay, Low-Side
Gate Rise Time, Low-Side
Gate Turn-Off Delay, Low-Side
Gate Fall Time, Low-Side
Sense Differential > 70mV, CT = 0pF
10
20
50
Note 4
Note 5
Note 6
Note 7
Note 4
Note 8
Note 9
Note 10
1.4
0.8
1.2
0.6
1.7
0.7
0.5
1.0
2.0
1.5
2.0
1.5
2.5
1.5
1.0
1.5
tDHL
tF
tDLH
tR
tDHL
tF
Note 1 Voltage remains low for time affected by C .
T
Note 2 When using sense MOSFETs, it is recommended that R
Note 3 DC measurement.
< 50Ω. Higher values may affect the sense MOSFET’s current transfer ratio.
SENSE
Note 4 Input switched from 0.8V (TTL low) to 2.0V (TTL high), time for Gate transition from 0V to 2V.
Note 5 Input switched from 0.8V (TTL low) to 2.0V (TTL high), time for Gate transition from 2V to 17V.
Note 6 Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 20V (Gate on voltage) to 17V.
Note 7 Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 17V to 2V.
Note 8 Input switched from 0.8V (TTL low) to 2.0V (TTL high), time for Gate transition from 2V to 10V.
Note 9 Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 15V (Gate on voltage) to 10V.
Note 10 Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 10V to 2V.
September 1999
181
MIC5022
MIC5022
Micrel
Typical Characteristics
Gate to Source Voltage
vs. Supply Voltage
Gate Turn-On Delay vs.
Supply Voltage
Supply Current vs.
Supply Voltage
6.0
25
20
15
10
5
2.5
2.0
1.5
1.0
0.5
0.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
VIN = 0V
VGATE = VSUPPLY + 4V
CL = CH = 1500pF
CBOOST = 0.01µF
VIN = 5V
NOTE: INCLUDES PROPAGATION
DELAY & CROSS CONDUCTION
LOCKOUT
0
5
10 15 20 25 30 35 40
(V)
5
10 15 20 25 30 35 40
5
10 15 20 25 30 35 40
V
V
(V)
V
(V)
SUPPLY
SUPPLY
SUPPLY
Gate Turn-On Delay vs.
Supply Voltage
Gate Turn-On/Off Delay vs.
Gate Capacitance
Gate Turn-On/Off Delay vs.
Gate Capacitance
2.5
2
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
3.5
3.0
2.5
2.0
1.5
1.0
VGATE H = VSUPPLY + 4V
CL = CH
VSUPPLY = 12V
VGATE L = 4V
CL = CH
VSUPPLY = 12V
1.5
1
LOW-SIDE
VGATE H = VSUPPLY + 10V
CL = CH = 1500pF
CBOOST = 0.01µF
HIGH-SIDE
NOTE: INCLUDES
PROPAGATION
DELAY & CROSS
CONDUCTION
LOCKOUT
PROP.
DELAY
PROP.
DELAY
NOTE: INCLUDES PROPAGATION
DELAY & CROSS CONDUCTION
LOCKOUT
0.5
0
NOTE: INCLUDES PROPAGATION
DELAY & CROSS CONDUCTION
LOCKOUT
5
10 15 20 25 30 35 40
0
1
2
3
4
5
0
1
2
3
4
5
1x10 1x10 1x10 1x10 1x10 1x10
(pF)
1x10 1x10 1x10 1x10 1x10 1x10
V
(V)
SUPPLY
C
C
(pF)
GATE
GATE
Overcurrent Retry Duty
Cycle vs. Timing Capacitance
Overcurrent Retry Duty
Input Current vs.
Input Voltage
Cycle vs. Timing Capacitance
25
25.0
100
80
60
40
20
0
tON = 5µS
VSUPPLY = 12V
tON = 5µS
V
SUPPLY = 12V
V
SUPPLY = 12V
20
15
10
5
20.0
15.0
10.0
5.0
HIGH SIDE
LOW SIDE
NOTE:
tON, tOFF TIME
INDEPENDENT
OF VSUPPLY
0
0.0
0
5
10
V
15
(V)
20
25
0.1
1
10
C
100 1000 10000
(pF)
0.1
1
10
C
100 1000 10000
(pF)
TL
IN
TH
Sense Threshold vs.
Temperature
80
70
60
50
40
30
20
-60 -30
0
30 60 90 120 150
TEMPERATURE (°C)
MIC5022
182
September 1999
MIC5022
Micrel
TTL (H)
0V
Input
Enable
Gate H
Gate L
TTL (H)
0V
15V (max.)
Source
15V (max.)
0V
50mV
0V
Sense H+, H–
Differential
50mV
0V
Sense L+, L–
Differential
Off
Fault
On
Timing Diagram 1. Normal Operation
5µs
20µs
TTL (H)
0V
Input
Enable
Gate H
Gate L
TTL (H)
0V
15V (max.)
0V
15V (max.)
0V
Sense H+, H–
Differential
Sense L+, L–
Differential
50mV
0V
50mV
0V
Off
Fault
On
Timing Diagram 2. Overcurrent Fault with Retry
5µs
TTL (H)
Input
0V
TTL (H)
Enable
0V
15V (max.)
Gate H
Source
15V (max.)
Gate L
0V
Sense H+, H–
50mV
0V
Differential
Sense L+, L–
Differential
50mV
0V
Off
Fault
On
Timing Diagram 3. Overcurrent Fault with Maintained Off
September 1999
183
MIC5022
MIC5022
Micrel
pin
Functional Description
Refer to the MIC5022 block diagram.
Input
cause it is on the high side of the load) raising the V
BOOST
voltage. The boost capacitor charge is directed through the
gate pin to quickly charge the FET’s gate to 15V maximum
above V . The internal charge pump maintains the gate
A signal greater than 1.4V (nominal) applied to the MIC5022
INPUT causes gate enhancement on an external MOSFET
connected to GATE H turning the high-side MOSFET on.
DD
voltage by supplying a small current as needed.
Overcurrent Limiting (High or Low-Side)
At the same time internal logic removes gate enhancement
from an external MOSFET connected to GATE L, turning the
low-side MOSFET off.
Current source I charges C
upon power up. An optional
INT
externalcapacitorconnectedtoC iskeptdischargedthrough
1
T
a FET Q1.
An internal pull-down resistor insures that an open INPUT
remains low, keeping the external high-side MOSFET turned
off and the low-side MOSFET turned on.
A fault condition (> 50mV from SENSE + to SENSE –) causes
the overcurrent comparator to enable current sink 2I which
in about 5µs
is discharged, the INPUT is disabled, the
and C are ready to be
charged. Since the INPUT is disabled the GATE output turns
1
overcomes current source I to discharge C
1
INT
Enable (Active Low)
time. When C
INT
A signal greater than 1.4V (nominal) applied to the MIC5022
ENABLE keeps both GATE outputs off. An internal pull-down
resistorinsuresthattheMIC5022isenabledifthepinisopen.
FAULT output is enabled, and C
INT
T
off.
Gate Outputs
When the GATE output turns off the FET, the overcurrent
signal is removed from the sense inputs which deactivates
Rapid rise and fall times on the GATE output are possible
because each input state change triggers a one-shot which
current sink 2I . This allows C
and the optional capacitor
1
INT
activatesahigh-valuecurrentsink(10I )forashorttime. This
connected to C to recharge. A Schmitt trigger delays the
2
T
draws a high current though a current mirror circuit causing
the output transistors to quickly charge or discharge the
external FET’s gate.
retry while the capacitor(s) recharge. Retry delay is in-
creased by connecting a capacitor connected to C (op-
T
tional).
A second current sink continuously draws the lower value of
current used to maintain the gate voltage for the selected
state.
The MIC5022’s low-side driver may be used without current
sensing by grounding both SENSE + and SENSE – pins. The
high-side driver may be used without current sensing by
connecting SENSE + and SENSE – to the source of the
external high-side MOSFET.
Internal 15V Zener diodes protect the external high-side and
low-side MOSFETs by limiting the gate to source voltage.
Fault Output
Charge Pump (High-Side)
The FAULT output is an open collector transistor. FAULT is
active at approximately the same time the output is disabled
by a fault condition (5µs after an overcurrent condition is
sensed). The FAULT output is open circuit (off) during each
successive retry (5µs).
Aninternalchargepumputilizesanexternal“boost”capacitor
connected between V
and the source of the external
BOOST
FET(refertoTypicalApplication). Theboostcapacitorstores
charge when the FET is off. As the FET begins to turn on the
voltage on the source side of the capacitor increases (be-
Typical Full-Bridge Application
+12V to +20V
MIC5022
MIC5022
VBOOST
Gate H
10µF
10µF
1
2
3
4
5
6
7
14
13
12
11
10
9
14
13
12
11
10
9
1
2
3
4
5
6
7
VDD
VBOOST
Gate H
VDD
0.01µF
0.01µF
TTL Input
(PWM signal)
TTL Input
(PWM signal)
Input
Input
Fault Sense H–
CTH Sense H+
Enable Gate L
CTL Sense L–
Gnd Sense L+
Sense H– Fault
Sense H+ CTH
Gate L Enable
Load
Sense L–
CTL
8
8
Sense L+ Gnd
Figure 1. Basic Full-Bridge Circuit
MIC5022
184
September 1999
MIC5022
Micrel
Applications Information
The MIC5022 MOSFET driver is designed for half-bridge
switching applications where overcurrent limiting and high
speedarerequired. TheMIC5022cancontrolMOSFETsthat
switch voltages up to 36V.
Circuits Without Current Sensing
Current sensing may be omitted by connecting the high-side
SENSE + and SENSE – pins to the source of the MOSFET or
the supply and the low-side SENSE + and SENSE – pins to
ground. Do not connect the high-side sense pins to ground.
TheMIC5022functionallyincludestheMIC5020andMIC5021
withadditionalcircuitrytocoordinatetheoperationofthehigh
and low-side drivers. Since most output considerations are
similar, refer to the MIC5020 and MIC5021 data sheets for
additional applications information.
Inductive Load Precautions
Circuits controlling inductive loads require precautions when
controlled by the MIC5022. Wire wound resistors, which are
sometimes used to simulate other loads, can also show
significant inductive properties.
Supply Voltage
The MIC5022’s supply input (V ) is rated up to 36V. The
supply voltage must be equal to or greater than the voltage
applied to the drain of the external N-channel MOSFET.
Sense Pin Considerations
DD
The sense pins of the MIC5022 are sensitive to negative
voltages. If a voltage spike is too negative (below approxi-
mately –0.5V), current will be drawn from functional sections
of the IC resulting in unpredictable circuit behavior or dam-
age. Resistors and Schottky diodes may be used to protect
the sense pins from the negative spikes. Refer to the
MIC5021 data sheet for details.
A 16V minimum supply is recommended to produce continu-
ous on-state, gate drive voltage for standard MOSFETs (10V
nominal gate enhancement).
Whenthedriverispoweredfroma12Vto16Vsupply, alogic-
level MOSFET is recommended (5V nominal gate enhance-
ment).
High-Side Sensing
PWMoperationmayproducesatisfactorygateenhancement
at lower supply voltages. This occurs when fast switching
repetition makes the boost capacitor a more significant
voltage supply than the internal charge pump.
For the high-side driver, sensing the current on the supply
side of the high-side MOSFET locates the SENSE pins away
from the inductive spike. Refer to the MIC5021 data sheet for
details.
Overcurrent Limiting
Low-Temperature Operation
Separate high and low-side 50mV comparators are provided
for current sensing. The low level trip point minimizes I R
losses when a power resistor is used for current sensing.
As the temperature of the MIC5022AJB (extended tempera-
ture range version—no longer available) approaches –55°C,
the driver’s off-state, gate-output offset from ground in-
creases. If the operating environment of the MIC5022AJB
includes low temperatures (–40°C to –55°C), add an external
2.2MΩ resistor from gate-to-source or from gate-to-ground.
This assures that the driver’s gate-to-source voltage is far
belowtheexternalMOSFET’sgatethresholdvoltage, forcing
the MOSFET fully off. Refer to the MIC5020 and MIC5021
data sheets for examples.
2
The adjustable retry feature can be used to handle loads with
high initial currents, such as lamps or heating elements, and
can be adjusted from the C connection.
T
C to ground causes maintained gate drive shutdown follow-
T
ing an overcurrent condition.
C open, or a capacitor to ground, causes automatic retry.
T
The default duty cycle (C open) is approximately 20% (the
T
The gate-to-source configuration is appropriate for resistive
and inductive loads. This also causes the smallest decrease
in gate output voltage.
high side is slightly greater than the low side). Refer to the
typical characteristics when selecting a capacitor for a re-
duced duty cycle.
The gate-to-ground configuration is appropriate for resistive,
inductive, or capacitive loads. This configuration will de-
crease the gate output voltage slightly more than the gate-to-
source configuration.
C through a pull-up resistor to V increases the duty cycle.
T
DD
Increasing the duty cycle increases the power dissipation in
the load and MOSFET under a “fault” condition. Circuits may
become unstable at a duty cycle of about 75% or higher,
depending on conditions. Caution: The MIC5022 may be
Full-Bridge Motor Control
damaged if the voltage applied to C exceeds the absolute
maximum voltage rating.
An application for two MIC5022s is the full-bridge motor
control circuit.
T
Boost Capacitor Selection
Two high or two low-side sense inputs may be used for
overcurrent detection. (Low-side sensing is shown in Fig-
ure 2). Sensing at four locations is usually unnecessary.
For 12V to 20V operation, the boost capacitor should be
0.01µF; and for 12V to 36V operation, the boost capacitor
should be 2.7nF; both connected between V
MOSFET source. The preferred configuration for 20V to 36V
operation is a 0.1µF capacitor connected between V
and the
When switching inductive loads, such as motors, it is desir-
able to place the high-side sense inputs on the supply side of
the MOSFETs. The helps prevent the inductive spikes that
occur upon load shutoff from affecting the sense inputs.
BOOST
BOOST
and V . Refer to the MIC5021 data sheet for examples.
DD
DonotconnectcapacitorsbetweenV
andtheMOSFET
BOOST
source and between V
and V
at the same time.
BOOST
DD
Larger capacitors than specified may damage the MIC5022.
September 1999
185
MIC5022
MIC5022
Micrel
+12V to +20V
MIC5022
MIC5022
VBOOST
Gate H
10µF
10µF
1
2
3
4
5
6
7
14
13
12
11
10
9
14
13
12
11
10
9
1
2
3
4
5
6
7
VDD
Input
VBOOST
Gate H
VDD
TTL Input
(PWM signal)
TTL Input
(PWM signal)
Input
Fault Sense H–
CTH Sense H+
Enable Gate L
CTL Sense L–
Gnd Sense L+
Sense H– Fault
Sense H+ CTH
Gate L Enable
0.01µF
0.01µF
M
Sense L–
CTL
RS2
RS1
8
8
Sense L+ Gnd
Figure 2. Full-Bridge Motor Control Application
Synchronous Rectifier Converter
The MIC5022 can be part of a synchronous rectifier in SMPS
(switch mode power supply) applications.
forced through the inductor to the output capacitor and load.
When the pass transistor is switched off, the synchronous
rectifier is switched on allowing current to continue to flow as
the inductor returns stored energy.
This circuit uses the MIC38C43 SMPS controller IC to switch
a pass transistor (Q1) and a “synchronous rectifier” transistor
(Q2) using the MIC5022.
The synchronous rectifier MOSFET has a lower voltage drop
than the forward voltage drop across a Schottky diode. This
increases converter efficiency which extends battery life in
portable equipment.
The MIC38C43 controller switches the transistors at 50kHz.
Output regulation is maintained using PWM. When the pass
transistor is on, the synchronous rectifier is off and current is
+12V
10k
0.1µF
470µF
25V
SMP06N06-14
Q1
MIC5022
13k
13
14
10
11
12
3
1
5
2
8
9
7
VOUT
0.1µF
V+
Gate H
VPP
70µH
5V, 8A
300k
5mΩ
0.15µF
47k
Enable
Input
S L+
S L–
MIC38C43
Gate L
S H+
S H–
Fault
4.7nF
1
2
3
4
8
7
6
5
Q2
Comp
VREF
VDD
1000µF
Low ESR
4.3k
FB
IS
VOUT
Gnd
Gnd
3.3k
RT/CT
2200pF
10k
Figure 3. 50kHz Synchronous Rectifier Converter
MIC5022
186
September 1999
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