National Semiconductor LMD18245 Technical data
LMD18245
3A, 55V DMOS Full-Bridge Motor Driver
LMD18245 3A, 55V DMOS Full-Bridge Motor Driver
March 2006
General Description
The LMD18245 full-bridge power amplifier incorporates all
the circuit blocks required to drive and control current in a
brushed type DC motor or one phase of a bipolar stepper
motor. The multi-technology process used to build the device
combines bipolar and CMOS control and protection circuitry
with DMOS power switches on the same monolithic structure. The LMD18245 controls the motor current via a fixed
off-time chopper technique.
An all DMOS H-bridge power stage delivers continuous output currents up to 3A (6A peak) at supply voltages up to 55V.
The DMOS power switches feature low R
efficiency, and a diode intrinsic to the DMOS body structure
eliminates the discrete diodes typically required to clamp
bipolar power stages.
An innovative current sensing method eliminates the power
loss associated with a sense resistor in series with the motor.
A four-bit digital-to-analog converter (DAC) provides a digital
path for controlling the motor current, and, by extension,
simplifies implementation of full, half and microstep stepper
motor drives. For higher resolution applications, an external
DAC can be used.
DS(ON)
for high
Features
n DMOS power stage rated at 55V and 3A continuous
n Low R
n Internal clamp diodes
n Low-loss current sensing method
n Digital or analog control of motor current
n TTL and CMOS compatible inputs
n Thermal shutdown (outputs off) at T
n Overcurrent protection
n No shoot-through currents
n 15-lead TO-220 molded power package
Applications
n Full, half and microstep stepper motor drives
n Stepper motor and brushed DC motor servo drives
n Automated factory, medical and office equipment
Functional Block and Connection Diagram
(15-Lead TO-220 Molded Power Package (T) )
of typically 0.3Ω per power switch
DS(ON)
= 155˚C
J
Order Number LMD18245T
See NS Package Number TA15A
© 2006 National Semiconductor Corporation DS011878 www.national.com
01187801
Connection Diagram
LMD18245
15-Lead TO-220 Molded Power Package
Order Number LMD18245T
See NS Package Number TA15A
Pinout Descriptions (See Functional Block
and Connection Diagrams)
Pin 1, OUT 1: Output node of the first half H-bridge.
Pin 2, COMP OUT: Output of the comparator. If the voltage
at CS OUT exceeds that provided by the DAC, the comparator triggers the monostable.
Pin 3, RC: Monostable timing node. A parallel resistorcapacitor network connected between this node and ground
sets the monostable timing pulse at about 1.1 RC seconds.
Pin 5, PGND: Ground return node of the power bridge. Bond
wires (internaI) connect PGND to the tab of the TO-220
package.
Pins 4 and 6 through 8, M4 through M1: Digital inputs of
the DAC. These inputs make up a four-bit binary number
with M4 as the most significant bit or MSB. The DAC provides an analog voltage directly proportional to the binary
number applied at M4 through M1.
Pin 9, V
Pin 10, BRAKE: Brake logic input. Pulling the BRAKE input
logic-high activates both sourcing switches of the power
bridge —effectively shorting the load. See Table 1. Shorting
the load in this manner forces the load current to recirculate
and decay to zero.
Pin 11, DIRECTION: Direction logic input. The logic level at
this input dictates the direction of current flow in the load.
See Table 1.
: Power supply node.
CC
Top View
01187802
Pin 12, SGND: Ground return node of all signal level circuits.
Pin 13, CS OUT: Output of the current sense amplifier. The
current sense amplifier sources 250 µA (typical) per ampere
of total forward current conducted by the upper two switches
of the power bridge.
Pin 14, DAC REF: Voltage reference input of the DAC. The
DAC provides an analog voltage equal to V
DAC REF
x D/16,
where D is the decimal equivalent (0–15) of the binary
number applied at M4 through M1.
Pin 15, OUT 2: Output node of the second half H-bridge.
TABLE 1. Switch Control Logic Truth Table
BRAKE DIRECTION MONO Active Switches
H X X Source 1, Source 2
L H L Source 2
L H H Source 2, Sink 1
L L L Source 1
L L H Source 1, Sink 2
X = don’t care
MONO is the output of the monostable.
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LMD18245
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
DC Voltage at:
OUT 1, V
COMP OUT, RC, M4, M3, M2, M1, BRAKE, +12V
, and OUT 2 +60V
CC
TO-220 (T
TO-220 (T
= 25˚C, Infinite Heatsink) 25W
A
= 25˚C, Free Air) 3.5W
A
ESD Susceptibility (Note 4) 1500V
Storage Temperature Range (T
) −40˚C to +150˚C
S
Lead Temperature (Soldering, 10 seconds) 300˚C
Operating Conditions (Note 1)
DIRECTION, CS OUT, and DAC REF
DC Voltage PGND to SGND
±
400mV
Continuous Load Current 3A
Peak Load Current (Note 2) 6A
Junction Temperature (T
) +150˚C
J(max)
Power Dissipation (Note 3) :
Temperature Range (T
Supply Voltage Range (V
CS OUT Voltage Range 0V to +5V
DAC REF Voltage Range 0V to +5V
MONOSTABLE Pulse Range 10 µs to 100 ms
) (Note 3) −40˚C to +125˚C
J
) +12V to +55V
CC
Electrical Characteristics (Note 2)
The following specifications apply for VCC= +42V, unless otherwise stated. Boldface limits apply over the operating temperature range, −40˚C ≤ T
Symbol Parameter Conditions Typical Limit Units
I
CC
Quiescent Supply Current DAC REF = 0V, VCC= +20V 8 mA
POWER OUTPUT STAGE
R
V
DIODE
T
rr
Q
t
D(ON)
DS(ON)
rr
Switch ON Resistance I
Body Diode Forward Voltage I
Diode Reverse Recovery Time I
Diode Reverse Recovery Charge I
Output Turn ON Delay Time
Sourcing Outputs I
Sinking Outputs I
t
D(OFF)
Output Turn OFF Delay Time
Sourcing Outputs I
Sinking Outputs I
t
ON
Output Turn ON Switching Time
Sourcing Outputs I
Sinking Outputs I
t
OFF
Output Turn OFF Switching Time
Sourcing Outputs I
Sinking Outputs I
t
pw
t
DB
Minimum Input Pulse Width Pins 10 and 11 2 µs
Minimum Dead Band (Note 6) 40 ns
CURRENT SENSE AMPLIFIER
Current Sense Output I
Current Sense Linearity Error 0.5A ≤ I
≤ +125˚C. All other limits apply for TA=TJ= 25˚C.
J
= 3A 0.3 0.4 Ω (max)
LOAD
I
= 6A 0.3 0.4 Ω (max)
LOAD
= 3A 1.0 V
DIODE
=1A 80 ns
DIODE
=1A 40 nC
DIODE
=3A 5 µs
LOAD
= 3A 900 ns
LOAD
= 3A 600 ns
LOAD
= 3A 400 ns
LOAD
=3A 40 µs
LOAD
=3A 1 µs
LOAD
= 3A 200 ns
LOAD
=3A 80 ns
LOAD
= 1A (Note 7) 200 µA (min)
LOAD
≤ 3A (Note 7)
LOAD
(Note 5) (Note 5) (Limits)
15 mA (max)
0.6 Ω (max)
0.6 Ω (max)
1.5 V(max)
250 175 µA (min)
300 µA (max)
325 µA (max)
±
6%
±
9 %(max)
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Electrical Characteristics (Note 2) (Continued)
The following specifications apply for VCC= +42V, unless otherwise stated. Boldface limits apply over the operating temperature range, −40˚C ≤ T
LMD18245
Symbol Parameter Conditions Typical Limit Units
CURRENT SENSE AMPLIFIER
Current Sense Offset I
DIGITAL-TO-ANALOG CONVERTER (DAC)
Resolution 4 Bits (min)
Monotonicity 4 Bits (min)
Total Unadjusted Error 0.125 0.25 LSB (max)
Propagation Delay 50 ns
I
REF
DAC REF Input Current DAC REF = +5V −0.5 µA
COMPARATOR AND MONOSTABLE
Comparator High Output Level 6.27 V
Comparator Low Output Level 88 mV
Comparator Output Current
Source 0.2 mA
Sink 3.2 mA
t
DELAY
Monostable Turn OFF Delay (Note 8) 1.2 µs
PROTECTION AND PACKAGE THERMAL RESISTANCES
Undervoltage Lockout, V
T
JSD
Shutdown Temperature, T
Package Thermal Resistances
θ
JC
θ
JA
Junction-to-Case, TO-220 1.5 ˚C/W
Junction-to-Ambient, TO-220 35 ˚C/W
LOGIC INPUTS
V
IL
V
IH
I
IN
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device
outside the rated Operating Conditions.
Note 2: Unless otherwise stated, load currents are pulses with widths less than 2 ms and duty cycles less than 5%.
Note 3: The maximum allowable power dissipation at any ambient temperature is P
operation, T
forcing T
junction-to-case thermal resistance of the package, θ
Note 4: ESD rating is based on the human body model of 100 pF discharged through a 1.5 kΩ resistor. M1, M2, M3 and M4, pins 8, 7, 6 and 4 are protected to
800V.
Note 5: All limits are 100% production tested at 25˚C. Temperature extreme limits are guaranteed via correlation using accepted SQC (Statistical Quality Control)
methods. All limits are used to calculate AOQL (Average Outgoing Quality Level). Typicals are at T
Note 6: Asymmetric turn OFF and ON delay times and switching times ensure a switch turns OFF before the other switch in the same half H-bridge begins to turn
ON (preventing momentary short circuits between the power supply and ground). The transitional period during which both switches are OFF is commonly referred
to as the dead band.
Note 7: (I
The current sense linearity is specified as the slope of the line between the 0.5A and 1A data points minus the slope of the line between the 2A and 3A data points
all divided by the slope of the line between the 0.5A and 1A data points.
Note 8: Turn OFF delay, t
DMOS switch beginning to turn OFF. With V
5V at 1.2V/µs, and t
Low Level Input Voltage −0.1 V (min)
High Level Input Voltage 2 V (min)
Input Current VIN=0Vor12V
is the ambient temperature in ˚C, and θJAis the junction-to-ambient thermal resistance in ˚C/W. Exceeding P
A
above 125˚C. If the junction temperature exceeds 155˚C, internal circuitry disables the power bridge. When a heatsink is used, θJAis the sum of the
J
LOAD,ISENSE
) data points are taken for load currents of 0.5A, 1A, 2A and 3A. The current sense gain is specified as I
DELAY
is measured as the time from the voltage at RC reaching 2V to the time the voltage at OUT 1 reaches 3V.
DELAY
≤ +125˚C. All other limits apply for TA=TJ= 25˚C.
J
(Note 5) (Note 5) (Limits)
=0A 5 µA
LOAD
20 µA (max)
0.5 LSB (max)
±
10 µA (max)
2.0 µs (max)
CC
5 V (min)
8 V (max)
J
155 ˚C
0.8 V (max)
12 V (max)
±
10 µA (max)
= (125 − TA)/θJA, where 125˚C is the maximum junction temperature for
Max
, and the case-to-ambient thermal resistance of the heatsink.
JC
= 25˚C and represent the most likely parametric norm.
J
, is defined as the time from the voltage at the output of the current sense amplifier reaching the DAC output voltage to the lower
= 32V, DIRECTION high, and 200Ω connected between OUT1 and VCC, the voltage at RC is increased from 0V to
CC
voids the Electrical Specifications by
max
SENSE/ILOAD
for the 1A data point.
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Typical Performance Characteristics
RDS(ON) vs Temperature RDS(ON) vs Load Current
LMD18245
RDS(ON) vs
Supply Voltage
Supply Current vs
Supply Voltage
01187829
01187830
Current Sense Output
vs Load Current
01187831 01187832
Supply Current vs
Temperature
01187833
01187834
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Functional Descriptions
TYPICAL OPERATION OF A CHOPPER AMPLIFIER
LMD18245
Chopper amplifiers employ feedback driven switching of a
power bridge to control and limit current in the winding of a
motor (Figure 1). The bridge consists of four solid state
power switches and four diodes connected in an H configuration. Control circuitry (not shown) monitors the winding
current and compares it to a threshold. While the winding
current remains less than the threshold, a source switch and
a sink switch in opposite halves of the bridge force the
supply voltage across the winding, and the winding current
increases rapidly towards V
As the winding current surpasses the threshold, the control
circuitry turns OFF the sink switch for a fixed period or
/R (Figure 1a and Figure 1d ).
CC
off-time. During the off-time, the source switch and the opposite upper diode short the winding, and the winding current recirculates and decays slowly towards zero (Figure 1b
and Figure 1e ). At the end of the off-time, the control circuitry turns back ON the sink switch, and the winding current
again increases rapidly towards V
/R (Figure 1a and Fig-
CC
ure 1d again). The above sequence repeats to provide a
current chopping action that limits the winding current to the
threshold (Figure 1g ). Chopping only occurs if the winding
current reaches the threshold. During a change in the direction of the winding current, the diodes provide a decay path
for the initial winding current (Figure 1c and Figure 1f ).
Since the bridge shorts the winding for a fixed period, this
type of chopper amplifier is commonly referred to as a fixed
off-time chopper.
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Functional Descriptions (Continued)
LMD18245
(a)
(b)
(e)
01187803
01187804
(c)
01187805
(d)
01187806
(g)
01187807
01187809
(f)
01187808
FIGURE 1. Chopper Amplifier Chopping States: Full VCCApplied Across the Winding (a) and (d), Shorted Winding (b)
and (e), Winding Current Decays During a Change in the Direction of the Winding Current (c) and (f), and the
Chopped Winding Current (g)
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