Datasheet

LT6108-1/LT6108-2
24
610812fa
TYPICAL APPLICATIONS
Simplified DC Motor Torque Control
Power-On Reset or Disconnect Using TimerBlox
®
Circuit
The figure above shows a simplified DC motor control
circuit. The circuit controls motor current, which is pro-
portional to motor torque; the LT6108 is used to provide
current feedback to an integrator that servos the motor
current to the current set point. The LTC
®
6992 is used to
convert the output of the difference amp to the motors
PWM control signal.
SENSEHI SENSELO
OUTA
8 1
6
5
7
2
3
4
LT6108-1
V
–
9k
100k
2
3
7
LTC6246
4
6
1
3
6
IRF640
5V
1N5818
0.1Ω
V
MOTOR
5
4
2
0.47µF
V
OUT
CURRENT SET POINT (0V TO 5V)
1k
1M
610812 TA04
1k
78.7k
100k
280k
INC
V
+
EN/RST
OUTC
RESET
100µF
+
–
LTC6992-1
V
+
GND
5V
1µF
BRUSHED
DC MOTOR
(0A TO 5A)
MABUCHI
RS-540SH
MOD
SET
OUT
DIV
–
+
V
+
V
–
V
–
4
610812 TA06
V
+
400mV
REFERENCE
V
+
R
IN
100Ω
R
SENSE
I
LOAD
OUTA 6
INC 5
7
SENSEHI
LT6108-1
5V
SENSELO
OUTC
EN/RST
8
1
3
2
R1
9.53k
R2
499Ω
R7
10k
R4
1M
R5
487k
R6
30k
TRIG
C1
0.1µF
Q1
2N2222
OUT
GND V
+
SET DIV
LTC6993-3
5V
CREATES A DELAYED
10µs RESET PULSE
ON START-UP
OPTIONAL:
DISCHARGES C1
WHEN SUPPLY
IS DISCONNECTED
–
+
The LTC6993-3 provides a 10µs reset pulse to the LT6108-1.
The reset pulse is delayed by R4 and C1 whose time constant
must be greater than 10ms and longer than the supply
turn-on time. Optional components R6 and Q1 discharge
capacitor C1 when the supply and/or ground are discon-
nected. This ensures that when the power supply and/or
ground are restored, capacitor C1 can fully recharge and
trigger the LTC6993-3 to produce another comparator reset
pulse. These optional components are particularly useful
if the power and/or ground connections are intermittent,
as can occur when PCB are plugged into a connector.