MIC5022

Micrel

MIC5022

178

September 1999

MIC5022

Half-Bridge MOSFET Driver

Features

· 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

Applications

· Motor control
· Switch-mode power supplies

General Description

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).

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 1

The MIC5022 then supplies a limited current (< 2mA), if
necessary, to maintain the output states.

Two overcurrent comparators with nominal trip voltages of
50mV make the MIC5022 ideal for use with current sensing
MOSFETs. External low value resistors may be used instead
of sensing MOSFETs for more precise overcurrent control.
Optional external capacitors placed on the C

and C

pins

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

provides a fault indication when either sense input is tripped.

The MIC5022 is available in 16-pin wide SOIC and 14-pin
plastic DIP packages.

Other members of the MIC502x family include the MIC5020
low-side driver and the MIC5021 high-side driver.

Typical Application

Input

Fault

Enable

Gnd

BOOST

Gate H

Sense H

Sense H+

Gate L

Sense L

Sense L+

10µF

2.7nF

+12V to +36V

MIC5022

TTL Input

(PWM signal)

DC Motor Control Application

Ordering Information

Part Number

Temperature Range

Package

MIC5022BWM

C to +85

16-pin Wide SOIC

MIC5022BN

C to +85

14-pin Plastic DIP

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Pin Description

DIP Pin No.

SOIC Pin No.

Pin Name

Pin Function

Supply: +12V to +36V. Decouple with

F capacitor.

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.

Fault

When either sense voltage exceeds threshold, open collector output is open
circuit for 5

s (t

G(ON)

), then pulled low for t

G(OFF)

. t

G(OFF)

is adjustable from

Retry Trimming Capacitor, High Side: Controls the off time (t

G(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.

Enable

Output Enable: Disables operation of the output drivers; active high. An
internal pull-down returns an open pin to logic low.

Retry Trimming Capacitor, Low Side: Same function as C

Gnd

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 R

SENSE

sets the load overcurrent trip point.

Sense L

Current Sense Comparator () Input, Low Side: Connect to the negative
side of the low-side sense resistor.

Gate L

Gate Drive, Low Side: Drives the gate of an external power MOSFET. Also
limits V

to 15V max. to prevent Gate to Source damage. Will sink and

source current.

Sense H +

Current Sense Comparator (+) Input, High Side: Connect to source of high-
side MOSFET. A built-in offset (nominal 50mV) in conjunction with R

SENSE

sets the load overcurrent trip point.

Source H

Current Sense Comparator () Input, High Side: Connect to the negative
side of the high-side sense resistor.

Gate H

Gate Drive, High Side: Drives the gate of an external power MOSFET. Also
limits V

to 15V max. to prevent Gate to Source damage. Will sink and

source current.

BOOST

Charge Pump Boost Capacitor: A bootstrap capacitor from V

BOOST

to the

MOSFET source pin supplies charge to quickly enhance the external
MOSFET's gate .

Pin Configuration

DIP Package

SOIC Package

(N)

(WM)

BOOST

Input

Fault

Enable

Gnd

Gate H

Sense H

Sense H+

Gate L

Sense L

Sense L+

BOOST

Input

Fault

Enable

Gnd

Gate H

Sense H

Sense H+

Gate L

Sense L

Sense L+

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September 1999

Block Diagram

INT

ONE-

SHOT

Gate L

Fault

OFF

Fault

Normal

10I

15V

Sense H

Sense H+

6V Internal Regulator

INT

50mV

Input

ONE-

SHOT

Gate H

OFF

Fault

Normal

10I

15V

CHARGE

PUMP

BOOST

Enable

Sense L

Sense L+

50mV

1.4V

Transistor Count: 188

Absolute Maximum Ratings

Supply Voltage (V

) .................................................. +40V

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

Timer Voltage (C

) ..................................................... +5.5V

BOOST

Capacitor .................................................... 0.01

Operating Ratings

Supply Voltage (V

) .................................... +12V to +36V

Temperature Range

SOIC ...................................................... 40

C to +85

PDIP ....................................................... 40

C to +85

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Electrical Characteristics

= 25

C, Gnd = 0V, V

= 12V, Gate C

= 1500pF (IRF540 MOSFET) unless otherwise specificed

Symbol

Parameter

Condition

Min

Typ

Max

Units

D.C. Supply Current

= 12V, Input = 0V

2.5

= 36V, Input = 0V

6.0

= 12V, Input = 5V

2.4

= 36V, Input = 5V

3.0

Input Threshold

0.8

1.4

2.0

Input Hysteresis

0.1

Input Pull-Down Current

Input = 5V

Enable Threshold

0.8

1.4

2.0

Enable Hysteresis

0.1

Fault Output

Fault Current = 1.6mA

0.15

0.4

Saturation Voltage

Note 1

Fault Output Leakage

Fault = 36V

0.01

Current Limit Thresh., Low-Side

Note 2

Current Limit Thresh., High-Side

Note 2

Gate On Voltage, High-Side

= 12V, Note 3

= 36V, Note 3

Gate On Voltage, Low-Side

= 12V, Note 3

= 36V, Note 3

G(ON)

Gate On Time, Fixed

Sense Differential > 70mV

G(OFF)

Gate Off Time, Adjustable

Sense Differential > 70mV, C

= 0pF

DLH

Gate Turn-On Delay, High-Side

Note 4

1.4

2.0

Gate Rise Time, High-Side

Note 5

0.8

1.5

DHL

Gate Turn-Off Delay, High-Side

Note 6

1.2

2.0

Gate Fall Time, High-Side

Note 7

0.6

1.5

DLH

Gate Turn-On Delay, Low-Side

Note 4

1.7

2.5

Gate Rise Time, Low-Side

Note 8

0.7

1.5

DHL

Gate Turn-Off Delay, Low-Side

Note 9

0.5

1.0

Gate Fall Time, Low-Side

Note 10

1.0

1.5

Note 1

Voltage remains low for time affected by C

Note 2

When using sense MOSFETs, it is recommended that R

SENSE

< 50

. Higher values may affect the sense MOSFET's current transfer ratio.

Note 3

DC measurement.

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.

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1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

SUPPLY

(mA)

SUPPLY

(V)

Supply Current vs.

Supply Voltage

= 0V

= 5V

GATE H

(V)

SUPPLY

(V)

Gate to Source Voltage

vs. Supply Voltage

0.0

0.5

1.0

1.5

2.0

2.5

ON 4V

(

SUPPLY

(V)

Gate Turn-On Delay vs.

Supply Voltage

GATE

= V

SUPPLY

+ 4V

= C

= 1500pF

BOOST

= 0.01

NOTE: INCLUDES PROPAGATION
DELAY & CROSS CONDUCTION
LOCKOUT

0.5

1.5

2.5

ON 10V

(

SUPPLY

(V)

Gate Turn-On Delay vs.

Supply Voltage

GATE H

= V

SUPPLY

+ 10V

= C

= 1500pF

BOOST

= 0.01

NOTE: INCLUDES PROPAGATION
DELAY & CROSS CONDUCTION
LOCKOUT

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1x10

(

GATE

(pF)

Gate Turn-On/Off Delay vs.

Gate Capacitance

HIGH-SIDE

GATE H

= V

SUPPLY

+ 4V

= C

SUPPLY

= 12V

NOTE: INCLUDES PROPAGATION
DELAY & CROSS CONDUCTION
LOCKOUT

PROP.
DELAY

1.0

1.5

2.0

2.5

3.0

3.5

1x10

(

GATE

(pF)

Gate Turn-On/Off Delay vs.

Gate Capacitance

LOW-SIDE

GATE L

= 4V

= C

SUPPLY

= 12V

NOTE: INCLUDES
PROPAGATION
DELAY & CROSS
CONDUCTION
LOCKOUT

PROP.
DELAY

Typical Characteristics

0.1

100

1000 10000

RETRY DUTY CYCLE (%)

(pF)

NOTE:
t

, t

OFF

TIME

INDEPENDENT
OF V

SUPPLY

Overcurrent Retry Duty

Cycle vs. Timing Capacitance

= 5

SUPPLY

= 12V

HIGH SIDE

0.0

5.0

10.0

15.0

20.0

25.0

0.1

100

1000 10000

RETRY DUTY CYCLE (%)

(pF)

= 5

SUPPLY

= 12V

Overcurrent Retry Duty

Cycle vs. Timing Capacitance

LOW SIDE

100

(

(V)

Input Current vs.

Input Voltage

SUPPLY

= 12V

-60 -30

90 120 150

VOLTAGE (mV)

TEMPERATURE (

Sense Threshold vs.

Temperature

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September 1999

Functional Description

Refer to the MIC5022 block diagram.

Input

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.

At the same time internal logic removes gate enhancement
from an external MOSFET connected to

GATE

L, turning the

low-side MOSFET off.

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.

Enable (Active Low)

A signal greater than 1.4V (nominal) applied to the MIC5022

ENABLE

keeps both

GATE

outputs off. An internal pull-down

resistor insures that the MIC5022 is enabled if the pin is open.

Gate Outputs

Rapid rise and fall times on the

GATE

output are possible

because each input state change triggers a one-shot which
activates a high-value current sink (10I

) for a short time. This

draws a high current though a current mirror circuit causing
the output transistors to quickly charge or discharge the
external FET's gate.

A second current sink continuously draws the lower value of
current used to maintain the gate voltage for the selected
state.

Internal 15V Zener diodes protect the external high-side and
low-side MOSFETs by limiting the gate to source voltage.

Charge Pump (High-Side)

An internal charge pump utilizes an external "boost" capacitor
connected between V

BOOST

and the source of the external

FET (refer to Typical Application). The boost capacitor stores
charge when the FET is off. As the FET begins to turn on the
voltage on the source side of the capacitor increases (be-

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

voltage by supplying a small current as needed.

Overcurrent Limiting (High or Low-Side)

Current source I

charges C

INT

upon power up. An optional

external capacitor connected to C

is kept discharged through

a FET Q1.

A fault condition (> 50mV from

SENSE

+ to

SENSE

) causes

the overcurrent comparator to enable current sink 2I

which

overcomes current source I

to discharge C

INT

in about 5

time. When C

INT

is discharged, the

INPUT

is disabled, the

FAULT

output is enabled, and C

INT

and C

are ready to be

charged. Since the

INPUT

is disabled the

GATE

output turns

off.

When the

GATE

output turns off the FET, the overcurrent

signal is removed from the sense inputs which deactivates
current sink 2I

. This allows C

INT

and the optional capacitor

connected to C

to recharge. A Schmitt trigger delays the

retry while the capacitor(s) recharge. Retry delay is in-
creased by connecting a capacitor connected to C

(op-

tional).

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.

Fault Output

The

FAULT

output is an open collector transistor.

FAULT

active at approximately the same time the output is disabled
by a fault condition (5

s after an overcurrent condition is

sensed). The

FAULT

output is open circuit (off) during each

successive retry (5

s).

Input

Fault

Enable

Gnd

BOOST

Gate H

Sense H

Sense H+

Gate L

Sense L

Sense L+

10µF

0.01µF

+12V to +20V

MIC5022

Input

Fault

Enable

Gnd

BOOST

Gate H

Sense H

Sense H+

Gate L

Sense L

Sense L+

10µF

MIC5022

0.01µF

TTL Input

(PWM signal)

TTL Input
(PWM signal)

Load

Figure 1. Basic Full-Bridge Circuit

Typical Full-Bridge Application

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Applications Information

The MIC5022 MOSFET driver is designed for half-bridge
switching applications where overcurrent limiting and high
speed are required. The MIC5022 can control MOSFETs that
switch voltages up to 36V.

The MIC5022 functionally includes the MIC5020 and MIC5021
with additional circuitry to coordinate the operation of the high
and low-side drivers. Since most output considerations are
similar,

refer to the MIC5020 and MIC5021 data sheets for

additional applications information.

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.

A 16V minimum supply is recommended to produce continu-
ous on-state, gate drive voltage for standard MOSFETs (10V
nominal gate enhancement).

When the driver is powered from a 12V to 16V supply, a logic-
level MOSFET is recommended (5V nominal gate enhance-
ment).

PWM operation may produce satisfactory gate enhancement
at lower supply voltages. This occurs when fast switching
repetition makes the boost capacitor a more significant
voltage supply than the internal charge pump.

Overcurrent Limiting

Separate high and low-side 50mV comparators are provided
for current sensing. The low level trip point minimizes I

losses when a power resistor is used for current sensing.

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.

to ground causes maintained gate drive shutdown follow-

ing an overcurrent condition.

open, or a capacitor to ground, causes automatic retry.

The default duty cycle (C

open) is approximately 20% (the

high side is slightly greater than the low side). Refer to the
typical characteristics when selecting a capacitor for a re-
duced duty cycle.

through a pull-up resistor to V

increases the duty cycle.

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

damaged if the voltage applied to C

exceeds the absolute

maximum voltage rating.

Boost Capacitor Selection

For 12V to 20V operation, the boost capacitor should be
0.01

F; and for 12V to 36V operation, the boost capacitor

should be 2.7nF; both connected between V

BOOST

and the

MOSFET source. The preferred configuration for 20V to 36V
operation is a 0.1

F capacitor connected between V

BOOST

and V

. Refer to the MIC5021 data sheet for examples.

Do not connect capacitors between V

BOOST

and the MOSFET

source and between V

BOOST

and V

at the same time.

Larger capacitors than specified may damage the MIC5022.

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.

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.

Sense Pin Considerations

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.

High-Side Sensing

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.

Low-Temperature Operation

As the temperature of the MIC5022AJB (extended tempera-
ture range version--no longer available) approaches 55

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

2.2M

resistor from gate-to-source or from gate-to-ground.

This assures that the driver's gate-to-source voltage is far
below the external MOSFET's gate threshold voltage, forcing
the MOSFET fully off. Refer to the MIC5020 and MIC5021
data sheets for examples.

The gate-to-source configuration is appropriate for resistive
and inductive loads. This also causes the smallest decrease
in gate output voltage.

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.

Full-Bridge Motor Control

An application for two MIC5022s is the full-bridge motor
control circuit.

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.

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.

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September 1999

Input

Fault

Enable

Gnd

BOOST

Gate H

Sense H

Sense H+

Gate L

Sense L

Sense L+

10µF

0.01µF

+12V to +20V

MIC5022

Input

Fault

Enable

Gnd

BOOST

Gate H

Sense H

Sense H+

Gate L

Sense L

Sense L+

10µF

MIC5022

0.01µF

TTL Input

(PWM signal)

TTL Input
(PWM signal)

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.

This circuit uses the MIC38C43 SMPS controller IC to switch
a pass transistor (Q1) and a "synchronous rectifier" transistor
(Q2) using the MIC5022.

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

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.

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.

Figure 3. 50kHz Synchronous Rectifier Converter

MIC38C43

0.1µF

300k

4.3k

OUT

5V, 8A

0.15µF

70µH

1000µF
Low ESR

0.1µF

SMP06N06-14

REF

Gnd

Comp

OUT

4.7nF

10k

13k

47k

3.3k

2200pF

470µF
25V

MIC5022

Gate H

S H+

Gate L

S H

Fault

S L

S L+

Gnd

Input

Enable

V+

+12V

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