LB1938FA Motor Driver IC Application Note

LB1938FA
Monolithic Digital IC
1ch, Low-saturation
Forward/Reverse Motor Driver
Application Note
http://onsemi.com
Overview
The LB1938FA is an H-bridge motor driver that supports low-voltage drive and features low-saturation
outputs in an ultraminiature slim package. The LB1938FA provides forward, reverse, brake, and standby
modes controlled by two input signals, and is an optimal DC motor driver for notebook personal computers,
digital cameras, cell phones, and other portable equipment.
Function
 Ultraminiature Micro8 package (3.0mm x 4.9mm x 1.1mm)
 The low saturation voltage means that the voltage applied to the motor is higher and IC heat generation is
reduced.
This allows this IC to be used in environments with higher ambient operating temperatures.
Output saturation voltage (high side + low side): VOsat = 0.15V typical (IO = 100mA)
 The wide usable voltage range and the low standby mode current drain of 0.1 µA make this IC optimal for
battery operated equipment.
 There are no constraints on the relationship between the input signal voltage and the supply voltage. For
example, this IC can be use at VCC = 3V and VIN = 5V.
 Thermal protection circuit limits the drive current and prevents the IC from causing a fire or being destroyed
if the IC chip temperature reaches or exceeds 180°C due to large currents flowing when the outputs are
shorted due to, for example, motor layer shorting or other phenomena.
Typical Applications
Package Dimensions
unit : mm (typ)
Pd max - Ta
700
Allowable Power Dissipation, Pd max - mW
 DSC
 Security camera
 CCTV
600
500
400
Mounted on a specified board
114.3mm76.1mm1.5 mm, glass epoxy resin
300
208
200
100
0
-30
0
30
60
Ambient Temperature, Ta -C
Semiconductor Components Industries, LLC, 2013
December, 2013
90
120
ILB01453
1/13
LB1938FA Application Note
Pin Assignment
Application Circuit Example
C1 = 0.1 to 10F
VCC
60k
CPU
3
60k
M
6
OUT2
80k
IN2
OUT1
7
Control block
2
80k
IN1
1
S-GND
4
8
P-GND
ILB01455
Cautions:
VCC and GND lines suffer substantial fluctuation in the current quantity, causing a problem of line oscillation in
certain cases. In this case, take following points into account:
(1) Use a thick and short wiring to reduce the wiring inductance.
(2) Insert a capacitor with satisfactory frequency characteristics near IC.
*) Electrostatic capacitor C1 is used to stabilize power. Requirement for capacitance value varies depends
on substrate wiring, motor, and power. The recommendation range of C1 is approximately 0.1μF to 10μF.
Please check supply voltage waveform when motor is under operation and use a capacitor for stable
operation.
(3) Connect S-GND to the control system GND on the CPU side and P-GND to the power system GND.
2/13
LB1938FA Application Note
Specifications
Absolute Maximum Ratings at Ta = 25C
Parameter
Symbol
Conditions
Ratings
Unit
Supply voltage
VCC max
10.5
V
Output current
IOUT max
800
mA
Output voltage
VOUT max
VCC+VSF
V
10
V
400
mW
Input applied voltage
VIH max
Allowable power dissipation
Pd max
Mounted on a specified board *
Operating temperature range
Topr
-30 to +85
C
Storage temperature range
Tstg
-55 to +150
C
Note *: Mounted on a specified board: 114.3mm x 76.1mm x 1.5mm, glass epoxy resin, wiring density 20%
Caution 1) Absolute maximum ratings represent the value which cannot be exceeded for any length of time.
Caution 2) Even when the device is used within the range of absolute maximum ratings, as a result of continuous usage
under high temperature, high current, high voltage, or drastic temperature change, the reliability of the IC may
be degraded. Please contact us for the further details.
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating
Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability.
Recommended Operating Conditions at Ta = 25C
Parameter
Symbol
Conditions
Ratings
min
typ
Unit
max
Supply voltage
VCC
2.2
10
V
Input high-level voltage
VIH
2.0
9.5
V
Input low-level voltage
VI L
-0.3
+0.3
V
Electrical Characteristics at Ta  25C, VCC = 3V
Parameter
Circuit current
Symbol
Ratings
min
typ
Unit
max
ICC1
Standby
0.1
5
A
ICC2
Forward/reverse drive
14
19
mA
ICC3
Output saturation voltage
Conditions
VOsat1
Brake
Upper + lower IO = 100mA
20
29
mA
0.15
0.2
V
0.35
0.5
V
for forward/reverse rotation
VOsat2
Upper + lower IO = 300mA
for forward/reverse rotation
VOsat3
Spark killer diode forward
Upper IO = 100mA for braking
0.1
0.15
V
VSF
IO = 300mA
0.9
1.7
V
IRS
VOUT = 10V
0.1
5
A
IIN
VIN = 5V
75
98
A
voltage
Spark killer diode inverse
current
Input current
Thermal protection operating
TSD
Design target value *
180
C
temperature
Note *: Design target value: Measurement with a single unit not made.
3/13
LB1938FA Application Note
Pin Functions
Pin No.
Pin name
Pin Function
2
IN1
Control signal input pin
3
IN2
Control signal input pin
7
OUT1
Out pin
6
OUT2
Out pin
1
VCC
Power supply voltage pin
4
S-GND
Signal ground pin
8
P-GND
Power ground pin
5
NC
No connect
Equivalent Circuit
4/13
LB1938FA Application Note
Truth Table
IN1
IN2
OUT1
OUT2
Mode
L
L
OFF
OFF
Standby
H
L
H
L
Forward rotation
L
H
L
H
Reverse rotation
H
H
H
H
Brake
Operation explanation
 Output stage transistor function

Thermal protection function
LB1938FA incorporates thermal shutdown circuitry. When junction temperature Tj exceeds 180C, the
output current flowing between OUT1 and OUT2 is reduced; therefore, the heat generation is reduced.
The thermal shutdown circuit does not guarantee the protection of the final product because it operates
when the temperature exceed the junction temperature of Tjmax=150C.
5/13
LB1938FA Application Note
VO(sat) - IO
0.4
0.3
0.2
0.1
0
0
100
200
300
400
Output current, IO - mA
VCC = 3V
0.4
IO = 3
0 0 mA
0.3
0.2
A
IO = 100m
0.1
0
-40
500
-20
0
20
40
60
80
100
Ambient temperature, Ta - C
ILB01459
ICC - Tc
28
VO(sat) - Ta
0.5
VCC = 3V
Output saturation voltage, VO(sat) - V
Output saturation voltage, VO(sat) - V
0.5
140
ILB01458
ICC - VCC
28
24
120
VCC = VIN
24
16
12
Forw
ard o
r
8
Bra
k
VC e mode
C =5
V
rever
se mo
de, V
CC = 5V 3V
Current drain, ICC - mA
Current drain, ICC - mA
e
Brake mod
20
4
20
16
Forward or
e IN1
reverse mod
IN2
4
6
12
8
4
3V
0
-40
-20
0
20
40
60
80
100
Case temperature, Tc - C
120
0
140
1
2
3
5
7
8
Supply voltage, VCC - V
IIN - VIN
160
0
ILB01457
9
10
ILB01460
ICC Standby Mode Temperature Characteristics
2.0
VCC = 3V
VCC = 11V
Current drain, ICC - A
Input current, IIN - A
1.6
120
80
40
1.2
0.8
0.4
0.29
0
0
1
2
3
4
5
6
7
8
Input voltage, VIN - V
9
10
ILB01461
0
-40
Under 0.01A
-20
0
20
40
60
80
Case temperature, Tc - C
100
120
140
ILB01462
IN Pin Input Current Temperature Characteristics
100
VIN = 5V
Input current, IIN - A
80
60
40
20
0
-40
-20
0
20
40
60
80
Case temperature, Tc - C
100
120
140
ILB01463
6/13
LB1938FA Application Note
Waveform example
*Please refer to the following test circuit diagram 1.
 No load VCC=3V IN2=“L”
High
 No load VCC=3V IN2=“H”
Ch1
IN1
5V/div
High
High
Ch2
VOUT1
2V/div
High
Low
Ch3
VOUT2
2V/div
High
High
Low
Off
High
Low
Off
High
Ch1
IN1
5V/div
Low
High
Ch2
VOUT1
2V/div
High
High
Ch3
VOUT2
2V/div
Low
T=2ms/div
T=2ms/div
 No load VCC=6V IN2=“L”
High
No load VCC=6V IN2=“H”
Ch1
IN1
5V/div
High
Low
High
Off
High
Low
High
High
Ch2
VOUT1
2V/div
Low
Off
High
High
High
 No load VCC=3V IN2=
Time scale expansion “fall time”
Low
High
Low
t=3.1us
High
High
T=1us/div
Ch3
VOUT2
2V/div
High
T=2ms/div
T=2ms/div
High
Ch2
VOUT1
2V/div
Low
Ch3
VOUT2
2V/div
Low
Ch1
IN1
5V/div
High
 No load VCC=3V IN2=“H”
Time scale expansion
Ch1
IN1
5V/div
Ch2
VOUT1
2V/div
Ch3
VOUT2
2V/div
Low
Low
High
“rise time”
High
Ch1
IN1
5V/div
High
Ch2
VOUT1
2V/div
t=2.2us
High
Ch3
VOUT2
2V/div
T=1us/div
7/13
LB1938FA Application Note
 No load VCC=6V IN2=“H”
Time scale expansion “fall time”
 No load VCC=6V IN2=“H”
Time scale expansion
Ch1
IN1
5V/div
Low
High
Low
High
High
t=2.4us
t=3.4us
High
Ch2
VOUT1
2V/div
Low
Ch2
VOUT1
2V/div
High
High
T=1us/div
 No load VCC=10V IN2=“H”
Time scale expansion
Low
Ch1
IN1
5V/div
Low
High
Ch2
VOUT1
5V/div
Low
High
Low
Ch3
VOUT2
5V/div
High
“rise time”
High
t=2.6us
High
t=3.8us
Ch3
VOUT2
5V/div
T=1us/div
 No load VCC=10V IN2=“H”
Time scale expansion “fall time”
High
Ch1
IN1
5V/div
High
Low
Ch3
VOUT2
5V/div
High
“rise time”
High
High
Ch1
IN1
5V/div
Ch2
VOUT1
5V/div
Ch3
VOUT2
5V/div
T=1us/div
T=1us/div
(Test circuit diagram 1)
10uF
VCC=3V/6V/10V
+
LB1938FA
VIN1=3V
(f=100Hz,duty=50%)
"H"
"L"
VIN2=3V
8/13
LB1938FA Application Note
*Please refer to the following test circuit diagram 2.

DC motor load VCC=3V IN2=“L”
Current waveform example
“motor start”
Low
Ch1
IN1
5V/div
High
Ch2
VOUT1
2V/div
High
Off
Off
Ch3
VOUT2
2V/div
Low
Ch4
Icoil
200mA/div
Forward
Standby
T=20ms/div
When DC motor starts up, the current value becomes high. However, rotation of DC motor starts, induced
voltage Ea is generated and current decreases according to the rotation frequency.
If a coil resistance is set to Rcoil and motor voltage is set to VCC, then motor current is obtained as follows:
Im = (VCC-Ea)/Rcoil.

DC motor load VCC=3V IN2=“H”
Current waveform example
“brake current”
High
Low
High
High
High
Ch2
VOUT1
2V/div
High
Ch3
VOUT2
2V/div
Low
High
High
Brake
Ch1
IN1
5V/div
Brake
Ch4
Icoil
200mA/div
Reverse
T=20ms/div
When DC motor is under rotation, if brake mode is set, then DC motor becomes short-brake status, and speed
falls rapidly.
In this case, current Im (Im = Ea / Rcoil) flows to the opposite direction by the induced voltage Ea generated
during motor rotation. If DC motor stops rotation, then Ea=0, and current becomes 0.
9/13
LB1938FA Application Note

DC motor load VCC=3V
Current waveform example
High
Low
High
High
High
High
Brake
“active reverse brake current”
High
Low
Low
Ch1
IN1
5V/div
Ch2
IN2
5V/div
Ch3
VOUT2
2V/div
Forward
Reverse
Ch4
Icoil
200mA/div
T=20ms/div
If rotation direction is switched while DC motor is rotating, then torque of reverse-rotation is generated, the
speed of motor rotation becomes slow and reverse rotation is performed.
In this case, since voltage of VCC is added to induced voltage Ea generated during motor rotation, the motor
current flows into the motor coil which is obtained as follows: Im= (VCC+Ea) / Rcoil.
When you switch from forward to reverse, if the current exceeds Iomax, make sure to set brake mode until the
induced voltage is reduced between forward and reverse.
(Test circuit diagram 2)
10/13
LB1938FA Application Note
OUT1
(Circuit diagram of the evaluation board)
OUT2
Evaluation board description
(NC) 5
OUT2 6
OUT1 7
P-GND 8
P-GND
10uF
C1 +
4 S-GND
3 IN2
1 VCC
2 IN1
LB1938FA
IC1
VCC
SW1 SW2
S-GND
IN2
IN1
VIN
*VIN terminal is a power supply input terminal for switches.
5V are to impress it and can perform the setting that is in a state by the switch operation and logic input.

Operation method
Power supply injection order: VCC  VIN

Truth value table
IN1
IN2
OUT1
OUT2
Mode
L
L
OFF
OFF
Standby
H
L
H
L
Forward
L
H
L
H
Reverse
H
H
H
H
Brake
11/13
LB1938FA Application Note
Recommended Soldering Footprint
12/13
LB1938FA Application Note
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