Agamem Microelectronics Inc.
PRELIMINARY
■
DESCRIPTION
AA51880
SERVO MOTOR CONTROLLER
The AA51880 is a BJT integrated circuit using in servo motor control applications. The built-in
voltage regulator provides the AA51880 with extremely stable output voltage. It also
incorporates a linear one-shot and pulse-width demodulator for improved positional accuracy.
■
FEATURES
• Built-in voltage regulator.
• Larger driving capability.
• Internal output NPN power transistor.
• Adjustable dead band range control.
• Incorporates a protection circuit for "H-Bridge" driving configuration.
• Small outline package.
■
APPLICATIONS
• Servo motor control.
• Radio controlled car, boat, and airplane.
• IA products (such as air-condition).
• Remote positioning.
■
BLOCK DIAGRAM
Note: Pin no. is for AA51880C/AA51880F; please refer to “PIN DESCRIPTION” for other package type.
©Copyright
Agamem Microelectronics Inc.
1
www.agamem.com.tw
2008/4/22
AGAMEM MICROELECTRONICS INCOPERATION RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE
TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. AGAMEM DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCTS OR CIRCUIT DESRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
Agamem Microelectronics Inc.
PRELIMINARY
■
PIN DESCRIPTION
AA51880
SERVO MOTOR CONTROLLER
PIN NO.
SSOP16 DIP14
1
2
3
5
6
7
8
9
10
11
4,12,13
14
1
3
6
8
7
12
9
10
5
4
PIN NAME
RT
EXP1
OUT1
OUT2
EXP2
CST
NC
VREG
VCC
RDB
GND
Timing Resistor
FUNCTION
External PNP Transistor 1 output
Output Driver 1
Output Driver 2
External PNP Transistor 2 output
Stretcher capacitor
No Connection
Regulated Voltage output
Power supply pin
Error pulse output
Ground pin
2
www.agamem.com.tw
2008/4/22
©Copyright
Agamem Microelectronics Inc.
AGAMEM MICROELECTRONICS INCOPERATION RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE
TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. AGAMEM DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCTS OR CIRCUIT DESRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
Agamem Microelectronics Inc.
PRELIMINARY
PIN NO.
SSOP16 DIP14
14
15
16
2
11
13
VIN
POT
CT
Input signal
Servo position voltage
Timing Capacitor
AA51880
SERVO MOTOR CONTROLLER
PIN NAME
FUNCTION
■
ABSOLUTE MAXIMUM RATINGS
Ta=25℃
SYMBOL PARAMETER
Vcc
Pd
Tstg
Supply voltage
Power dissipation
Storage temperature range
RATINGS
4.8~7
300
－25~＋125
UNIT
V
mW
℃
■
ELECTRICAL CHARACTERISTICS
Ta=25
℃
, Vcc=4.8V
SYMBOL
ICC
VOL
VOH
IPNP
VREG
IREG
PARAMETER
Operating current
Output voltage "L"
Output voltage "H"
TEST CONDITIONS
When output is OFF
When output is ON
Load resistor 20Ω
Load resistor 240Ω
LIMITS
UNIT
MIN TYP MAX
-
5
8
mA
-
-
3.5
30
2.3
4
25
0.1
-
-
2.45
-
28
0.2
-
-
2.6
-
mA
V
V
mA
V
mA
External PNP transistor
Load resistor 240Ω
drive current
Regulator output
voltage
Regulator output
current
Load capacitor 0.1uF
Load resistor 500Ω
©Copyright
Agamem Microelectronics Inc.
3
www.agamem.com.tw
2008/4/22
AGAMEM MICROELECTRONICS INCOPERATION RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE
TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. AGAMEM DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCTS OR CIRCUIT DESRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
Agamem Microelectronics Inc.
PRELIMINARY
■
FUNCTIONAL DESCRIPTION
(1) Voltage Regulator
AA51880
SERVO MOTOR CONTROLLER
This circuit is composed of a band gap circuit, and outputs a 2.45-volt temperature
compensated reference voltage. This reference voltage is stabilized when the supply voltage
is variable.
(2) Saw tooth wave & One-Shot Generator
Connect a capacitor to CT pin will generate a triangular wave by constant current charging. A
typical value is 0.1uF. The constant current is determined by a resistor connected to RT pin. A
typical capacitor of approximately 0.1uF should be connected in parallel with the resistor to
increase stability.
(3) Servo Position & Over-Time logic
This circuitry consists of a pulse width comparator, which compares the servo position
detection signal (POT pin) from the one-shot timer (CT pin) whose period depends on the
resistance of a potentiometer connected to the servo's drive shaft. This feedback is what
provides the stability for the control circuitry.
(4) Pulse Stretcher
The difference between the servo control signal and the feedback signal is the error signal.
This error signal is used to toggle the direction the current flows through the servo. The
function of this pulse stretcher is to “stretch” the small error signal long enough and increases
the duty cycle to the motor for it can maintain sufficient holding force. The circuit also
implements a “dead band” function that prevents servo jitter and hunting. This is a range over
which differences between the input and reference signals will not cause servo operation.
When the signal differences exceed this “dead band” range, drive to the motor occurs. servo’s
drive shaft. The dead band will change according to the value of resistor connected to the RDB
pin.
(5) Directional Logic Control
The comparator circuit compares pulses from the servo control input (VIN pin) and the voltage
controlled pulse generator and provides either a positive or a negative output depending on
whether the signal pulse width is larger or smaller than the position generator’s output pulse
(POT pin). Application of this error voltage to the motor driver circuit causes the motor to turn in
a direction that will minimize the error until both pulse widths are the same.
(6) PWM Control
This signal generated by directional logic control block is used to control a flip-flop that toggles
the direction the current flows through the motor. The outputs of the flip-flop drive an H-Bridge
output driver block that handles the high current going through the motor. This blocks output
will be turned on or off with each input pulse based on the status of the directional logic. The
©Copyright
Agamem Microelectronics Inc.
4
www.agamem.com.tw
2008/4/22
AGAMEM MICROELECTRONICS INCOPERATION RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE
TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. AGAMEM DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCTS OR CIRCUIT DESRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
Agamem Microelectronics Inc.
PRELIMINARY
AA51880
SERVO MOTOR CONTROLLER
PWM drive techniques provide the benefits of reduced power dissipation, improved servo
motor performance and positively affect system efficiency.
(7) Output driver
The output driver controls the servo current direction. For light load application, the servo can
be connected with OUT1 and OUT2 pin only. For heavy load application, the EXP1 and EXP2
pin will be connected to the base of the external PNP transistor. It drives in an H-bridge
configuration (The sink NPN drivers are built inside the chip).
■
TYPICAL APPLICATION EXAMPLE
A. Mini-Servo Application (No external drivers needed)
VCC
10
EXP1
2
C8 103pF
OUT1 3
VIN 14
OUT2
EXP2
5
6
VR1
5KΩ
VREG 9
RT
1
CT
16
POT
15
RDB CST
GND GND GND
11
R3
1KΩ
C3
0.1uF
C1
0.1uF
C2
0.1uF
7
4
12
13
R1
470KΩ
R7
1KΩ
R2
20KΩ
R4 150KΩ
C4
0.22uF
C5
4.7uF
©Copyright
Agamem Microelectronics Inc.
5
www.agamem.com.tw
2008/4/22
AGAMEM MICROELECTRONICS INCOPERATION RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE
TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. AGAMEM DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCTS OR CIRCUIT DESRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
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