August 1999

MIC5031

Micrel

MIC5031

High-Speed High-Side MOSFET Driver

Not Recommended for New Designs

General Description

The MIC5031 MOSFET driver is designed to switch an
N-channel enhancement-type MOSFET from a TTL control
signal in a high-side switch application. The MIC5031 pro-
vides overcurrent protection, can accommodate loads with
high-inrush current, and is designed to survive automotive
power disturbances. This driver is suitable for up to 30kHz
PWM operation with 0% to 100% duty cycle.

The MIC5031 is powered by the +4.5V to +30V load voltage.
An external bootstrap capacitor and internal charge pump
drive the gate output higher than the supply voltage. The
bootstrap capacitor provides speed, while the charge pump
can sustain the high gate output voltage continuously.

The MIC5031 features a resistor programmable overcurrent
shutdown (circuit breaker) function that monitors the voltage
drop across the external MOSFET. A capacitor program-
mable shutdown delay allows a high-inrush current load to be
energized without causing undesired shutdown. An open-
load detection feature is included and can be used by adding
an external high-value resistor.

The MIC5031 is protected against automotive load dump and
reverse battery conditions. The driver is also protected from
excessive power dissipation by an internal overtemperature
shutdown circuit.

An open-collector fault flag output indicates overcurrent,
overtemperature, or open-load fault conditions.

Typical Application

On
Off

FLG

VDD

CTL

100k

* Sets Overcurrent Trip to MOSFET V

102mV

Optional Resistor for Open-Load Detection

Optional Capacitor for Overcurrent Delay

Optional Resistor and Capacitor for Power-up Sequence

+4.5V to +30V

MIC5031

CP1+

CP1

CP2+

CP2

DLY

GND

15µF

50pF

12k*

0.1µF

1k*

Normal
Fault

51k

0.01µF

Enable

Disable

IRF540

0.1µF

2N5822

100µF

100nF

10k

0.01µF

High-Side Power Switch and Circuit Breaker

Features

· +4.5V to +30V operation
· Fast gate drive

(rise time = 70ns, fall time = 50ns,

with 1000pF load and 5V supply)

· Overcurrent detection across MOSFET
· Overcurrent shutdown delay
· Charge pump for high-side dc applications
· TTL compatible input
· Overtemperature shutdown
· Automotive load dump protection
· Reverse battery protection
· Open-collector fault flag
· Near zero-current disable state

Applications

· Automotive power switch
· Automotive PWM control
· Circuit breaker
· PWM circuits

Ordering Information

Part Number

Temperature Range

Package

MIC5031BM

C to +85

16-lead SOIC

Micrel, Inc. · 1849 Fortune Drive · San Jose, CA 95131 · USA · tel + 1 (408) 944-0800 · fax + 1 (408) 944-0970 · http://www.micrel.com

MIC5031

Micrel

MIC5031

August 1999

Pin Configuration

CP1

DLY

CTL

GND

CP2+

CP1+

VDD

CP2

FLG

16-lead SOIC (M)

Pin Description

Pin Number

Pin Name

Pin Function

FLG

Fault Flag: (Output): Open-collector output sinks current upon overcurrent,
open-load, or overtemperature detection. 10mA maximum load.

DLY

Overcurrent Delay Time Capacitor: Optional. Capacitor to ground delays
activation of overcurrent shutdown.

CTL

Control (Input): TTL compatible on/off control input. Logic high drives the
gate output above the supply voltage. Logic low forces the gate output near
ground. Logic low also resets the overcurrent fault latch.

Enable (Input): CMOS compatible input. Logic high enables the charge
pump. Logic low disables the charge pump and draws near zero supply
current.

GND

Ground: Power return.

Internal Supply Storage Capacitor: 10

F external capacitor to GND.

Provides additional current to internal circuitry during switching transitions.

VDD

Supply (Input): +4.5V to +30V supply.

CP1

Charge Pump Capacitor #1: Refer to CP1+.

CP2

Charge Pump Capacitor #2: Refer to CP2+.

CP1+

Charge Pump Capacitor #1: External 0.01

F voltage tripler capacitor.

CP2+

Charge Pump Capacitor #2: External 0.01

F voltage tripler capacitor.

Bootstrap Capacitor: 0.1

F capacitor to source for fastest rise time.

Source: Source connection to external MOSFET.

Reference Voltage Resistor: Resistor to VDD provides a reference voltage
drop. A voltage drop across the external MOSFET that is greater than the
voltage drop across the reference resistor indicates an overcurrent condition.
(

Refer to applications section) Zero temperature coefficient resistor

recommended.

Reference Current Resistor: Resistor to GND sets constant current value
through RV resistor (

Refer to applications section) and matches tempera-

ture compensation of RV resistor. Zero temperature coefficient resistor
recommended.

Gate (Output) : Gate connection to external MOSFET.

August 1999

MIC5031

Micrel

Electrical Characteristics

= 12V; C

= 0.1

F, CP1 = CP2 = 0.01

F; T

= 25

C; unless noted

Symbol

Parameter

Condition

Min

Typ

Max

Units

Supply current

= 0V, V

CTL

= 0V

0.3

= 12V, V

CTL

= 0V

1.0

= 12V, V

CTL

= 5V

0.72

DDR

Reverse voltage leakage current

= 12V

0.2

CTL

Control input voltage threshold

1.55

CTLH

Control input voltage hysteresis

0.2

0.5

1.0

CTL

Control input current

0.1

Enable input voltage threshold

Enable input current

0.1

IOS

Overcurrent comparator offset

Current limit reference current

= 12.0k

100

103

SHDL

Overcurrent shut down delay

DLY

= 50pF

Gate drive voltage

= 12V, V

CTL

= 5V

DLR

Gate turn-on delay

= 12V, C

= 1000p

420

Gate rise time

= 1000pF

DLF

Gate turnoff delay

= 1000pF

300

Gate fall time

= 1000pF

OLTH

Open-load threshold voltage

= 12V, V

CTL

= 0V

6.3

Overtemperature shut down

= 12V, V

CTL

= 5V

140

OTH

Overtemp. shut down hysteresis

= 12V, V

CTL

= 5V

Charge pump frequency

= 5V, Note 1

190

kHz

FLG

Flag active voltage

open load error, I

FLG

= 2mA (sink)

0.2

General Note: Devices are ESD protected; however, handling precautions are recommended.

Note 1:

Oscillator burst mode at V

5.2V.

Absolute Maximum Ratings

Supply Voltage (V

) .................................................. +36V

Enable Input Voltage (V

) ......................................... +36V

Control Input Voltage (V

CTL

)

15V .................................................................. V

> 15V ............................................................... +15V

Flag Output Voltage (V

FLG

) ......................................... +36V

Reference Voltage Input (V

) .................................... +36V

Junction Temperature (T

) ........................................ 150

Operating Ratings

Supply Voltage (V

) ................................... +4.5V to +30V

Ambient Temperature Range (T

)

A-temperature range ............................ 55

C to +125

B-temperature range .............................. 40

C to +85

Package Thermal Resistance (

)

SOIC ................................................................. 115

C/W

August 1999

MIC5031

Micrel

Functional Description

Refer to "Functional Diagram."

The MIC5031 is a noninverting device. Applying a CMOS
logic high signal to EN (enable input) activates the driver's
internal circuitry. Applying a TTL logic high signal to CTL
(control input) produces gate drive output. The G (gate)
output is used to turn on an external N-channel MOSFET.

Control

CTL (control) is a TTL compatible input. The threshold is
approximately 1.4V, independent of the supply voltage.

The falling edge of a signal applied to CTL also resets the
overcurrent lockout latch.

Enable

EN (enable) is a CMOS compatible input. EN enables or
disables all internal circuitry. The enable threshold is approxi-
mately half the supply voltage. The MIC5031 supply current
is near zero when the driver is disabled (low). See "Applica-
tions Information: Power-Up Sequence."

Charge Pump

The charge pump produces a voltage that is higher than the
supply voltage. This higher voltage is required to drive the
external N-channel MOSFET in high-side switch circuits.

The charge pump consists of an oscillator and a voltage
tripler. When the driver is enabled, the charge pump is
switched on and off to regulate its output voltage.

External capacitors C1 and C2 are required. The charge
pump will not operate without these capacitors.

Bootstrap Capacitor

The external bootstrap capacitor is necessary to achieve the
fastest gate rise times. The bootstrap capacitor (C3) supplies
additional current at a higher voltage to the gate drive
regulator as the MOSFET is switched on.

When the MOSFET is off, the gate drive regulator voltage is
applied to the boost capacitor . As the MOSFET turns on, the
MOSFET source-to-ground voltage increases. The increas-
ing source voltage is added to the voltage across the capaci-
tor for a voltage doubling effect.

Gate Drive Regulator

The gate drive regulator manages the voltage from the
bootstrap capacitor, the supply, and the charge pump.

The gate drive regulator charges the bootstrap capacitor
when the MOSFET is off and limits the voltage from the
bootstrap capacitor as the MOSFET is switched on. It also
performs skip-mode control by switching the charge pump on
and off to regulate the gate drive output voltage.

Gate Output

When the MIC5031 is enabled and CTL is high, the gate
driver steers regulated voltage to G (gate output). When CTL
is low, the gate driver grounds G. This respectively charges
or discharges the external MOSFET's gate, .

Current Sense

Refer to the "Voltage Reference (Simplified)" diagram.

The MIC5031 detects an overcurrent condition by comparing
the voltage drop across the external MOSFET to a reference
voltage drop created across R1. If V

exceeds V

, a

comparator (not shown) shuts off the external MOSFET by
way of the current limit delay, lockout latch, and logic.

The bandgap reference, op amp and NPN create a constant
voltage (1.23V) across R2. This results in a constant current,
I

, through R2. Ignoring a small amount of base current, the

same current (I

) flows through R1. R1 is selected to

achieve the desired reference voltage drop, V

. Refer to the

applications section for formulas.

Supply

1.23V

Bandgap

Reference

External

N-Channel

MOSFET

Load

1.23V

Voltage Reference (Simplified)

An overcurrent condition also activates the fault flag output
when the lockout latch is activated.

Overcurrent-Shutdown Delay

The overcurrent-shutdown delay circuit permits a delay be-
tween overcurrent detection and latch activation for high-
inrush current loads.

The delay can be increased by adding capacitance from DLY
to GND.

Open-Load Detect

The open load detect resistor is an external high-value pull-
up resistor that causes the source voltage of the external
MOSFET to increase when the load is missing.

The MIC5031 monitors the S-pin voltage only when the gate
driver is off. If the voltage on the S-pin rises above the open-
load detect threshold, the fault flag is activated.

Overtemperature Detect

The overtemperature detect circuit switches the logic to turn
the output off at approximately 140

C. An overtemperature

shutdown condition is restored to normal automatically When
the device cools to about 130

C (10

C hysteresis).

An overtemperature condition also activates the fault flag
output.

Fault Flag

FLT (fault flag) is an open-collector NPN transistor. Fault is
active (pulls collector near ground) upon overcurrent, open-
load, or overtemperature.

MIC5031

Micrel

MIC5031

August 1999

Applications Information

Power-Up Sequence

The supply voltage (V

) must be applied to VDD before EN

is asserted. If EN is not required for the application, an RC
network must be used to delay the voltage rise applied to EN
with respect to VDD. See Figure 1.

On
Off

FLG

VDD

CTL

+4.5V to +30V

MIC5031

CP1+

CP1

CP2+

CP2

DLY

GND

15µF

12k*

0.1µF

0.01µF

IRF540

0.1µF

2N5822

100µF

100nF

0.01µF

10k

Figure 1. Enable Application

Refer to "Typical Application" for controlling EN from open-
collector or open-drain logic. The 10k resistor and 0.01

capacitor connected to VDD, GND, and EN keep EN low
during power up before the open-collector or open-drain logic
becomes active.

The 10k resistor and 0.01

F capacitor can be omitted if EN

is held low by the external logic until VDD is powered.

Overcurrent Detection

Using the MOSFET manufacturer's data and the maximum
allowable load current, determine the maximum drain-to-
source voltage drop, V

, that will occur across the external

MOSFET in normal operation. This will also be the reference
voltage and the overcurrent trip voltage, V

= maximum R

DS(on)

maximum load current

Supply

1.23V

Bandgap

Reference

External

N-Channel

MOSFET

Load

1.23V

Figure 2. Resistor Calculations

Reference Current Resistor

Resistor R2 sets the reference current. For most applica-
tions, a reference current of 100

A is suggested.

where:

R2 = reference current resistor (

)

= reference current (A) [R2 = 12k

for

approximately 100

Reference Voltage Resistor

The reference voltage resistor value is calculated from the
reference current and the reference voltage (overcurrent
drop voltage).

where:

R1 = reference voltage resistor (

)

= reference voltage (V) [see above]

= reference current (A) [see above]

Overcurrent Delay Capacitor

For lamp switching applications, the delay capacitor (C

DLY

)

may be as high as several microfarads. Lamps often have an
inrush current of 10

their steady-state operating current. In

PWM applications, pay attention to the input frequency vs.
the overcurrent delay. They can conflict with each other if not
properly planned.

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