1997

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MIC5018

Micrel

MIC5018

IttyBittyTM High-Side MOSFET Driver

Preliminary Information

General Description

The MIC5018 IttyBittyTM high-side MOSFET driver is de-
signed to switch an N-channel enhancement-type MOSFET
from a TTL compatible control signal in high- or low-side
switch applications. This driver features the tiny 4-lead
SOT-143 package.

The MIC5018 is powered from a +2.7V to +9V supply and
features extremely low off-state supply current. An internal
charge pump drives the gate output higher than the driver
supply voltage and can sustain the gate voltage indefinitely.
An internal zener diode limits the gate-to-source voltage to a
safe level for standard N-channel MOSFETs.

In high-side configurations, the source voltage of the MOS-
FET approaches the supply voltage when switched on. To
keep the MOSFET turned on, the MIC5018's output drives
the MOSFET gate voltage higher than the supply voltage. In
a typical high-side configuration, the driver is powered from
the load supply voltage. Under some conditions, the MIC5018
and MOSFET can switch a load voltage that is slightly higher
than the driver supply voltage.

In a low-side configuration, the driver can control a MOSFET
that switches any voltage up to the rating of the MOSFET.
The gate output voltage is higher than the typical 3.3V or 5V
logic supply and can fully enhance a standard MOSFET.

The MIC5018 is available in the SOT-143 package and
is rated for 40

C to +85

C ambient temperature range.

Typical Applications

Features

· +2.7V to +9V operation
· 150

A typical supply current at 5V supply

A typical standby (off) current

· Charge pump for high-side low-voltage applications
· Internal zener diode gate-to-ground MOSFET protection
· Operates in low- and high-side configurations
· TTL compatible input
· ESD protected

Applications

· Battery conservation
· Power bus switching
· Solenoid and motion control
· Lamp control

Ordering Information

Part Number

Temp. Range

Package

Marking

MIC5018BM4

C to +85

SOT-143

H10

On
Off

CTL

GND

MIC5018

4.7µF

IRFZ24*
N-Channel
MOSFET

+5V

Load

* International Rectifier

100m

, 17A max.

TO-220 package

Low-Voltage High-Side Power Switch

On
Off

CTL

GND

MIC5018

4.7µF

Si9410DY*
N-channel
MOSFET

LOAD SUPPLY

Load

+2.7 to +9V

Load voltage limited only by
MOSFET drain-to-source rating

* Siliconix

30m

, 7A max., 30V V

max.

8-lead SOIC package

Low-Side Power Switch

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MIC5018

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Electrical Characteristics

Parameter

Condition (Note 1)

Min

Typ

Max

Units

Supply Current

SUPPLY

= 3.3V

CTL

= 0V

0.01

CTL

= 3.3V

140

SUPPLY

= 5V

CTL

= 0V

CTL

= 5V

150

300

Control Input Voltage

2.7V

SUPPLY

CTL

for logic 0 input

0.8

2.7V

SUPPLY

CTL

for logic 1 input

2.0

SUPPLY

CTL

for logic 1 input

2.4

SUPPLY

Control Input Current

2.7V

SUPPLY

0.01

Control Input Capacitance

Note 2

Zener Diode Output Clamp

SUPPLY

= 9V

Gate Output Voltage

SUPPLY

= 2.7V

6.3

7.1

SUPPLY

= 3.0V

7.1

8.2

SUPPLY

= 4.5V

11.4

13.4

Gate Output Current

SUPPLY

= 5V

OUT

= 10V, Note 3

9.5

Gate Turn-On Time

SUPPLY

= 4.5V

= 1000pF, Note 4

0.75

1.5

= 3000pF, Note 4

2.1

4.2

Gate Turn-Off Time

SUPPLY

= 4.5V

= 1000pF, Note 5

= 3000pF, Note 5

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

Note 1:

Typical values at T

= 25

C. Minimum and maximum values indicate performance at 40

+85

C. Parts production tested at 25

Note 2:

Guaranteed by design.

Note 3:

Resistive load selected for V

OUT

= 10V.

Note 4:

Turn-on time is the time required for gate voltage to rise to 4V greater than the supply voltage. This represents a typical MOSFET gate
threshold voltage.

Note 5:

Turn-off time is the time required for the gate voltage to fall to 4V above the supply voltage. This represents a typical MOSFET gate threshold
voltage.

Test Circuit

5V
0V

CTL

GND

MIC5018

SUPPLY

OUT

0.1µF

Absolute Maximum Ratings

Supply Voltage (V

SUPPLY

) ........................................... +10V

Control Voltage (V

CTL

) ................................. 0.6V to +16V

Gate Voltage (V

) ....................................................... +16V

Ambient Temperature Range (T

) ............. 40

C to +85

Lead Temperature, Soldering 10sec. ........................ 300

Package Thermal Resistance

SOT-143

..................................................... 220

C/W

SOT-143

..................................................... 130

C/W

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Typical Characteristics

Note 4

0.2

0.4

0.6

0.8

1.0

SUPPLY CURRENT (mA)

SUPPLY VOLTAGE (V)

Supply Current

vs. Supply Voltage

-40

125

120

160

10 12 14 16

OUTPUT CURRENT (

OUTPUT VOLTAGE (V)

Gate Output Current

vs. Output Voltage

SUPPLY

= 9V

1000 2000 3000 4000 5000

TURN-OFF TIME (

CAPACITANCE (pF)

Full Turn-Off Time

vs. Load Capacitance

SUPPLY

= 3V

Note 6

Note 4:

= 25

C, V

SUPPLY

= 5V unless noted.

Note 5:

Full turn-on time is the time between V

CTL

rising to 2.5V and the V

rising to 90% of its steady on-state value.

Note 6:

Full turn-off time is the time between V

CTL

falling to 0.5V and the V

falling to 10% of its steady on-state value.

1000 2000 3000 4000 5000

TURN-ON TIME (ms)

CAPACITANCE (pF)

Full Turn-On Time

vs. Load Capacitance

SUPPLY

= 3V

Note 5

OUTPUT VOLTAGE (V)

SUPPLY VOLTAGE (V)

Gate Output Voltage

vs. Supply Voltage

-40

125

100

120

10 12 14 16

OUTPUT CURRENT (

OUTPUT VOLTAGE (V)

Gate Output Current

vs. Output Voltage

= -55

125

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Functional Description

Refer to the functional diagram.

The MIC5018 is a noninverting device. Applying a 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.

Supply

VS (supply) is rated for +2.7V to +9V. An external capacitor
is recommended to decouple noise.

Control

CTL (control) is a TTL compatible input. CTL must be forced
high or low by an external signal. A floating input may cause
unpredictable operation.

A high input turns on Q2, which sinks the output of current
source I1, making the input of the first inverter low. The
inverter output becomes high enabling the charge pump.

Charge Pump

The charge pump is enabled when CTL is logic high. The
charge pump consists of an oscillator and voltage quadrupler

Functional Diagram

CHARGE

PUMP

CTL

R2
15k

R1 2k

GND

MIC5018

+2.7V to +9V

Load

On
Off

I1
20µA

D1
16V

D2
35V

D3 16V

Functional Diagram with External Components

(High-Side Driver Configuration)

). Output voltage is limited to 16V by a zener diode. The

charge pump output voltage will be approximately:

= 4

SUPPLY

2.8V, but not exceeding 16V.

The oscillator operates from approximately 70kHz to approxi-
mately 100kHz depending upon the supply voltage and
temperature.

Gate Output

The charge pump output is connected directly to the G (gate)
output. The charge pump is active only when CTL is high.
When CTL is low, Q3 is turned on by the second inverter and
discharges the gate of the external MOSFET to force it off.

If CTL is high, and the voltage applied to VS drops to zero, the
gate output will be floating (unpredictable).

ESD Protection

D1 and D2 clamp positive and negative ESD voltages. R1
isolates the gate of Q2 from sudden changes on the CTL
input. Q1 turns on if the emitter (CTL input) is forced below
ground to provide additional input protection. Zener D3 also
clamps ESD voltages for the gate (G) output.

MIC5018

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1997

Application Information

Supply Bypass

A capacitor from VS to GND is recommended to control
switching and supply transients. Load current and supply
lead length are some of the factors that affect capacitor
size requirements.

A 4.7

F or 10

F aluminum electrolytic or tantalum capacitor

is suitable for many applications.

The low ESR (equivalent series resistance) of tantalum
capacitors makes them especially effective, but also makes
them susceptible to uncontrolled inrush current from low
impedance voltage sources (such as NiCd batteries or auto-
matic test equipment). Avoid instantaneously applying volt-
age, capable of high peak current, directly to or near tantalum
capacitors without additional current limiting. Normal power
supply turn-on (slow rise time) or printed circuit trace resis-
tance is usually adequate for normal product usage.

MOSFET Selection

The MIC5018 is designed to drive N-channel enhancement-
type MOSFETs. The gate output (G) of the MIC5018 pro-
vides a voltage, referenced to ground, that is greater than the
supply voltage. Refer to the "Typical Characteristics: Gate
Output Voltage vs. Supply Voltage" graph.

The supply voltage and the MOSFET drain-to-source
voltage drop determine the gate-to-source voltage.

= V

SUPPLY

)

where:

= gate-to-source voltage (enhancement)

= gate voltage (from graph)

SUPPLY

= supply voltage

= drain-to-source voltage (approx. 0V at

low current, or when fully enhanced)

CTL

GND

MIC5018

SUPPLY

Load

LOAD

Figure 1. Voltages

The performance of the MOSFET is determined by the gate-
to-source voltage. Choose the type of MOSFET according to
the calculated gate-to-source voltage.

Standard MOSFET

Standard MOSFETs are fully enhanced with a gate-to-source
voltage of about 10V. Their absolute maximum gate-to-
source voltage is

20V.

With a 5V supply, the MIC5018 produces a gate output of
approximately 15V. Figure 2 shows how the remaining
voltages conform. The actual drain-to-source voltage drop

across an IRFZ24 is less than 0.1V with a 1A load and 10V
enhancement. Higher current increases the drain-to-source
voltage drop, increasing the gate-to-source voltage.

CTL

GND

MIC5018

4.7µF

+5V

Load

Logic

High

10V

approx. 0V

15V

Voltages are approximate

* International Rectifier

standard MOSFET

IRFZ24*

To demonstrate
this circuit, try a
2

, 20W

load resistor .

Figure 2. Using a Standard MOSFET

The MIC5018 has an internal zener diode that limits the gate-
to-ground voltage to approximately 16V.

Lower supply voltages, such as 3.3V, produce lower gate
output voltages which will not fully enhance standard
MOSFETs. This significantly reduces the maximum current
that can be switched. Always refer to the MOSFET data sheet
to predict the MOSFET's performance in specific applica-
tions.

Logic-Level MOSFET

Logic-level N-channel MOSFETs are fully enhanced with a
gate-to-source voltage of approximately 5V and generally
have an absolute maximum gate-to-source voltage of

10V.

CTL

GND

MIC5018

4.7µF

+3.3V

Load

Logic

High

5.7V

approx. 0V

3.3V

Voltages are approximate

* International Rectifier

logic-level MOSFET

IRLZ44*

To demonstrate
this circuit, try
5

, 5W or

, 1/4W

load resistors.

Figure 3. Using a Logic-Level MOSFET

Refer to figure 3 for an example showing nominal voltages.
The maximum gate-to-source voltage rating of a logic-level
MOSFET can be exceeded if a higher supply voltage is used.
An external zener diode can clamp the gate-to-source volt-
age as shown in figure 4. The zener voltage, plus its
tolerance, must not exceed the absolute maximum gate
voltage of the MOSFET.

CTL

GND

MIC5018

SUPPLY

Load

5V < V

< 10V

Protects gate of

logic-level MOSFET

Logic-level
N-channel
MOSFET

Figure 4. Gate-to-Source Protection

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Split Power Supply

Refer to figure 6. The MIC5018 can be used to control a 12V
load by separating the driver supply from the load supply.

CTL

GND

MIC5018

4.7µF

+12V

Load

Logic

High

approx. 0V

12V

15V

Voltages are approximate

* International Rectifier

logic-level MOSFET

IRLZ44*

+5V

To demonstrate
this circuit, try a
40

, 5W or

100

, 2W

load resistor.

Figure 6. 12V High-Side Switch

A logic-level MOSFET is required. The MOSFET's maximum
current is limited slightly because the gate is not fully en-
hanced. To predict the MOSFETs performance for any pair
of supply voltages, calculate the gate-to-source voltage and
refer to the MOSFET data sheet.

= V

LOAD SUPPLY

)

is determined from the driver supply voltage using the

"Typical Characteristics: Gate Output Voltage vs. Supply
Voltage" graph.

Low-Side Switch Configuration

The low-side configuration makes it possible to switch a
voltage much higher than the MIC5018's maximum supply
voltage.

On
Off

CTL

GND

MIC5018

4.7µF

IRF540*
N-channel
MOSFET

+80V

Load

+2.7 to +9V

* International Rectifier

standard MOSFET
BV

DSS

= 100V

To demonstrate
this circuit, try
1k, 10W or
33k, 1/4W
load resistors.

Figure 7. Low-Side Switch Configuration

The maximum switched voltage is limited only by the
MOSFET's maximum drain-to-source ratings.

A gate-to-source zener may also be required when the
maximum gate-to-source voltage could be exceeded due to
normal part-to-part variation in gate output voltage. Other
conditions can momentarily increase the gate-to-source volt-
age, such as turning on a capacitive load or shorting a load.

Inductive Loads

Inductive loads include relays, and solenoids. Long leads
may also have enough inductance to cause adverse effects
in some circuits.

On
Off

CTL

GND

MIC5018

4.7µF

+2.7V to +9V

Schottky
Diode

Figure 5. Switching an Inductive Load

Switching off an inductive load in a high-side application
momentarily forces the MOSFET source negative (as the
inductor opposes changes to current). This voltage spike can
be very large and can exceed a MOSFET's gate-to-source
and drain-to-source ratings. A Schottky diode across the
inductive load provides a discharge current path to minimize
the voltage spike. The peak current rating of the diode should
be greater than the load current.

In a low-side application, switching off an inductive load will
momentarily force the MOSFET drain higher than the supply
voltage. The same precaution applies.

Part Number MIC5018