LM5112
LM5112 Tiny 7A MOSFET Gate Driver
Literature Number: SNVS234B
LM5112
Tiny 7A MOSFET Gate Driver
General Description
The LM5112 MOSFET gate driver provides high peak gate
drive current in the tiny LLP-6 package (SOT23 equivalent
footprint) or an 8-Lead exposed-pad MSOP package, with
improved power dissipation required for high frequency op-
eration. The compound output driver stage includes MOS
and bipolar transistors operating in parallel that together sink
more than 7A peak from capacitive loads. Combining the
unique characteristics of MOS and bipolar devices reduces
drive current variation with voltage and temperature. Under-
voltage lockout protection is provided to prevent damage to
the MOSFET due to insufficient gate turn-on voltage. The
LM5112 provides both inverting and non-inverting inputs to
satisfy requirements for inverting and non-inverting gate
drive with a single device type.
Features
nCompound CMOS and bipolar outputs reduce output
current variation
n7A sink/3A source current
nFast propagation times (25 ns typical)
nFast rise and fall times (14 ns/12 ns rise/fall with 2 nF
load)
nInverting and non-inverting inputs provide either
configuration with a single device
nSupply rail under-voltage lockout protection
nDedicated input ground (IN_REF) for split supply or
single supply operation
nPower Enhanced 6-pin LLP package (3.0mm x 3.0mm)
or thermally enhanced MSOP8-EP package
nOutput swings from V
CC
to V
EE
which can be negative
relative to input ground
Block Diagram
20066801
Block Diagram of LM5112
April 2006
LM5112 Tiny 7A MOSFET Gate Driver
© 2006 National Semiconductor Corporation DS200668 www.national.com
Pin Configurations
20066802
LLP-6
20066817
MSOP8-EP
Ordering Information
Order Number Package Type
NSC Package
Drawing Supplied As
LM5112MY Exposed DAP MSOP8-EP MUY08A 1000 shipped in Tape & Reel
LM5112MYX Exposed DAP MSOP8-EP MUY08A 3500 shipped in Tape & Reel
LM5112SD LLP-6 SDE06A 1000 shipped in Tape & Reel
LM5112SDX LLP-6 SDE06A 4500 shipped in Tape & Reel
Pin Descriptions
Pin Name Description Application Information
LLP-6 MSOP-8
1 4 IN Non-inverting input pin TTL compatible thresholds. Pull up to VCC when
not used.
2 3 VEE Power ground for driver outputs Connect to either power ground or a negative
gate drive supply for positive or negative voltage
swing.
3 6 VCC Positive Supply voltage input Locally decouple to VEE. The decoupling
capacitor should be located close to the chip.
4 7 OUT Gate drive output Capable of sourcing 3A and sinking 7A. Voltage
swing of this output is from VEE to VCC.
5 1 IN_REF Ground reference for control
inputs
Connect to power ground (VEE) for standard
positive only output voltage swing. Connect to
system logic ground when VEE is connected to a
negative gate drive supply.
6 2 INB Inverting input pin TTL compatible thresholds. Connect to IN_REF
when not used.
- - - 5, 8 N/C Not internally connected
- - - - - - Exposed
Pad
Exposed Pad, underside of
package
Internally bonded to the die substrate. Connect to
VEE ground pin for low thermal impedance.
LM5112
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
CC
to V
EE
−0.3V to 15V
V
CC
to IN_REF −0.3V to 15V
IN/INB to IN_REF −0.3V to 15V
IN_REF to V
EE
−0.3V to 5V
Storage Temperature Range −55˚C to +150˚C
Maximum Junction Temperature +150˚C
Operating Junction Temperature −40˚C+125˚C
ESD Rating 2kV
Electrical Characteristics T
J
= −40˚C to +125˚C, V
CC
= 12V, INB = IN_REF = V
EE
= 0V, No Load on out-
put, unless otherwise specified.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
SUPPLY
V
CC
V
CC
Operating Range V
CC
– IN_REF and V
CC
-V
EE
3.5 14 V
UVLO V
CC
Under-voltage Lockout (rising) V
CC
– IN_REF 2.4 3.0 3.5 V
V
CCH
V
CC
Under-voltage Hysteresis 230 mV
I
CC
V
CC
Supply Current 1.0 2.0 mA
CONTROL INPUTS
V
IH
Logic High 2.3 V
V
IL
Logic Low 0.8 V
V
thH
High Threshold 1.3 1.75 2.3 V
V
thL
Low Threshold 0.8 1.35 2.0 V
HYS Input Hysteresis 400 mV
I
IL
Input Current Low IN = INB = 0V -1 0.1 1 µA
I
IH
Input Current High IN = INB = V
CC
-1 0.1 1 µA
OUTPUT DRIVER
R
OH
Output Resistance High I
OUT
= -10mA (Note 2) 30 50 Ω
R
OL
Output Resistance Low I
OUT
= 10mA (Note 2) 1.4 2.5 Ω
I
SOURCE
Peak Source Current OUT = V
CC
/2, 200ns pulsed
current
3A
I
SINK
Peak Sink Current OUT = V
CC
/2, 200ns pulsed
current
7A
SWITCHING CHARACTERISTICS
td1 Propagation Delay Time Low to
High,
IN/ INB rising ( IN to OUT)
C
LOAD
= 2 nF, see Figure 1 25 40 ns
td2 Propagation Delay Time High to
Low,
IN / INB falling (IN to OUT)
C
LOAD
= 2 nF, see Figure 1 25 40 ns
tr Rise time C
LOAD
=2nF,seeFigure 1 14 ns
tf Fall time C
LOAD
=2nF,seeFigure 1 12 ns
LATCHUP PROTECTION
AEC –Q100, METHOD 004 T
J
= 150˚C 500 mA
THERMAL RESISTANCE
θ
JA
Junction to Ambient,
0 LFPM Air Flow
LLP-6 Package
MSOP8-EP Package
40
60 ˚C/W
θ
JC
Junction to Case LLP-6 Package
MSOP8-EP Package
7.5
4.7 ˚C/W
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device
is intended to be functional. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: The output resistance specification applies to the MOS device only. The total output current capability is the sum of the MOS and Bipolar devices.
LM5112
www.national.com3
Timing Waveforms
20066804
(a)
20066805
(b)
FIGURE 1. (a) Inverting, (b) Non-Inverting
LM5112
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Typical Performance Characteristics
Supply Current vs Frequency Supply Current vs Capacitive Load
20066807
20066808
Rise and Fall Time vs Supply Voltage Rise and Fall Time vs Temperature
20066809 20066810
Rise and Fall Time vs Capacitive Load Delay Time vs Supply Voltage
20066811 20066812
LM5112
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Typical Performance Characteristics (Continued)
Delay Time vs Temperature RDSON vs Supply Voltage
20066813 20066814
UVLO Thresholds and Hysteresis vs Temperature Peak Current vs Supply Voltage
20066815 20066816
LM5112
www.national.com 6
Simplified Application Block Diagram
Detailed Operating Description
The LM5112 is a high speed , high peak current (7A) single
channel MOSFET driver. The high peak output current of the
LM5112 will switch power MOSFET’s on and off with short
rise and fall times, thereby reducing switching losses con-
siderably. The LM5112 includes both inverting and non-
inverting inputs that give the user flexibility to drive the
MOSFET with either active low or active high logic signals.
The driver output stage consists of a compound structure
with MOS and bipolar transistor operating in parallel to opti-
mize current capability over a wide output voltage and oper-
ating temperature range. The bipolar device provides high
peak current at the critical Miller plateau region of the MOS-
FET V
GS
, while the MOS device provides rail-to-rail output
swing. The totem pole output drives the MOSFET gate be-
tween the gate drive supply voltage V
CC
and the power
ground potential at the V
EE
pin.
The control inputs of the driver are high impedance CMOS
buffers with TTL compatible threshold voltages. The nega-
tive supply of the input buffer is connected to the input
ground pin IN_REF. An internal level shifting circuit connects
the logic input buffers to the totem pole output drivers. The
level shift circuit and separate input/output ground pins pro-
vide the option of single supply or split supply configurations.
When driving the MOSFET gates from a single positive
supply, the IN_REF and V
EE
pins are both connected to the
power ground.
The isolated input and output stage grounds provide the
capability to drive the MOSFET to a negative V
GS
voltage for
a more robust and reliable off state. In split supply configu-
ration, the IN_REF pin is connected to the ground of the
controller which drives the LM5112 inputs. The V
EE
pin is
connected to a negative bias supply that can range from the
IN_REF potential to as low as 14 V below the Vcc gate drive
supply. For reliable operation, the maximum voltage differ-
ence between V
CC
and IN_REF or between V
CC
and V
EE
is
14V.
The minimum recommended operating voltage between Vcc
and IN_REF is 3.5V. An Under Voltage Lock Out (UVLO)
circuit is included in the LM5112 which senses the voltage
difference between V
CC
and the input ground pin, IN_REF.
When the V
CC
to IN_REF voltage difference falls below 2.8V
the driver is disabled and the output pin is held in the low
state. The UVLO hysteresis prevents chattering during
20066803
FIGURE 2. Simplified Application Block Diagram
LM5112
www.national.com7
Detailed Operating Description
(Continued)
brown-out conditions; the driver will resume normal opera-
tion when the V
CC
to IN_REF differential voltage exceeds
3.0V.
Layout Considerations
Attention must be given to board layout when using LM5112.
Some important considerations include:
1. A Low ESR/ESL capacitor must be connected close to
the IC and between the V
CC
and V
EE
pins to support
high peak currents being drawn from V
CC
during turn-on
of the MOSFET.
2. Proper grounding is crucial. The driver needs a very low
impedance path for current return to ground avoiding
inductive loops. Two paths for returning current to
ground are a) between LM5112 IN_REF pin and the
ground of the circuit that controls the driver inputs and b)
between LM5112 V
EE
pin and the source of the power
MOSFET being driven. Both paths should be as short as
possible to reduce inductance and be as wide as pos-
sible to reduce resistance. These ground paths should
be distinctly separate to avoid coupling between the high
current output paths and the logic signals that drive the
LM5112. With rise and fall times in the range of 10 to
30nsec, care is required to minimize the lengths of cur-
rent carrying conductors to reduce their inductance and
EMI from the high di/dt transients generated when driv-
ing large capacitive loads.
3. If either channel is not being used, the respective input
pin (IN or INB) should be connected to either V
EE
or V
CC
to avoid spurious output signals.
Thermal Performance
INTRODUCTION
The primary goal of the thermal management is to maintain
the integrated circuit (IC) junction temperature (Tj) below a
specified limit to ensure reliable long term operation. The
maximum T
J
of IC components should be estimated in worst
case operating conditions. The junction temperature can be
calculated based on the power dissipated on the IC and the
junction to ambient thermal resistance θ
JA
for the IC pack-
age in the application board and environment. The θ
JA
is not
a given constant for the package and depends on the PCB
design and the operating environment.
DRIVE POWER REQUIREMENT CALCULATIONS IN
LM5112
LM5112 is a single low side MOSFET driver capable of
sourcing / sinking 3A / 7A peak currents for short intervals to
drive a MOSFET without exceeding package power dissipa-
tion limits. High peak currents are required to switch the
MOSFET gate very quickly for operation at high frequencies.
The schematic above shows a conceptual diagram of the
LM5112 output and MOSFET load. Q1 and Q2 are the
switches within the gate driver. Rg is the gate resistance of
the external MOSFET, and Cin is the equivalent gate capaci-
tance of the MOSFET. The equivalent gate capacitance is a
difficult parameter to measure as it is the combination of Cgs
(gate to source capacitance) and Cgd (gate to drain capaci-
tance). The Cgd is not a constant and varies with the drain
voltage. The better way of quantifying gate capacitance is
the gate charge Qg in coloumbs. Qg combines the charge
required by Cgs and Cgd for a given gate drive voltage
Vgate. The gate resistance Rg is usually very small and
losses in it can be neglected. The total power dissipated in
the MOSFET driver due to gate charge is approximated by:
P
DRIVER
=V
GATE
xQ
G
xF
SW
Where
F
SW
= switching frequency of the MOSFET.
For example, consider the MOSFET MTD6N15 whose gate
charge specified as 30 nC for V
GATE
= 12V.
Therefore, the power dissipation in the driver due to charging
and discharging of MOSFET gate capacitances at switching
frequency of 300 kHz and V
GATE
of 12V is equal to
P
DRIVER
= 12V x 30 nC x 300 kHz = 0.108W.
In addition to the above gate charge power dissipation, -
transient power is dissipated in the driver during output
transitions. When either output of the LM5112 changes state,
current will flow from V
CC
to V
EE
for a very brief interval of
time through the output totem-pole N and P channel
MOSFETs. The final component of power dissipation in the
driver is the power associated with the quiescent bias cur-
rent consumed by the driver input stage and Under-voltage
lockout sections.
Characterization of the LM5112 provides accurate estimates
of the transient and quiescent power dissipation compo-
nents. At 300 kHz switching frequency and 30 nC load used
in the example, the transient power will be 8 mW. The 1 mA
nominal quiescent current and 12V V
GATE
supply produce a
12 mW typical quiescent power.
Therefore the total power dissipation
P
D
= 0.118 + 0.008 + 0.012 = 0.138W.
We know that the junction temperature is given by
T
J
=P
D
xθ
JA
+T
A
Or the rise in temperature is given by
T
RISE
=T
J
−T
A
=P
D
xθ
JA
20066806
FIGURE 3.
LM5112
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Thermal Performance (Continued)
For LLP-6 package, the integrated circuit die is attached to
leadframe die pad which is soldered directly to the printed
circuit board. This substantially decreases the junction to
ambient thermal resistance (θ
JA
). By providing suitable
means of heat dispersion from the IC to the ambient through
exposed copper pad, which can readily dissipate heat to the
surroundings, θ
JA
as low as 40˚C / Watt is achievable with
the package. The resulting Trise for the driver example
above is thereby reduced to just 5.5 degrees.
Therefore T
RISE
is equal to
T
RISE
= 0.138 x 40 = 5.5˚C
For MSOP8-EP θ
JA
is typically 60˚C/W.
LM5112
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Physical Dimensions inches (millimeters) unless otherwise noted
6-Lead LLP Package
NS Package Number SDE06A
8-Lead eMSOP-8 Package
NS Package Number MUY08A
LM5112
www.national.com 10
Notes
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
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LM5112 Tiny 7A MOSFET Gate Driver
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