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DRV102 Datasheet, PDF (10/23 Pages) Burr-Brown (TI) – PWM SOLENOID/VALVE DRIVER | |||
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ADJUSTABLE DUTY CYCLE
The DRV102âs externally adjustable duty cycle provides an
accurate means of controlling power delivered to the load.
Duty cycle can be set from 10% to 90% with an external
resistor, analog voltage, or the output of a D/A converter.
Reduced duty cycle results in reduced power dissipation.
This keeps the DRV102 and load cooler, resulting in in-
creased reliability for both devices. PWM frequency is a
constant 24kHz.
Resistor-Controlled Duty Cycle
Duty cycle is independently programmed with a resistor
(RPWM) connected between the Duty Cycle Adjust pin and
ground. Increased resistor values correspond to decreased
duty cycles. Table II provides resistor values for typical duty
cycles. Resistor values for additional duty cycles can be
obtained from Figure 4. For reference purposes, the equation
for calculating RPWM is included in Figure 4.
DUTY CYCLE
10
20
30
40
50
60
70
80
90
RESISTOR(1)
RPWM (kâ¦)
536
137
66.5
39.2
24.9
16.2
10.5
6.65
4.42
VOLTAGE(2)
VPWM (V)
3.67
3.31
2.91
2.49
2.07
1.66
1.26
0.88
0.56
NOTES: (1) Resistor values listed are nearest 1% standard values. (2) Do not
drive pin below 0.1V. For additional values, see âDuty Cycle vs Voltageâ typical
performance curve.
TABLE II. Duty Cycle Adjust. TA= +25°C, VS = +24V.
Voltage-Controlled Duty Cycle
Duty cycle can also be programmed with an analog voltage,
VPWM. With VPWM â 0.5V, duty cycle is 100%. Increasing
this voltage results in decreased duty cycles. For 0% duty
cycle, VPWM is approximately 4V. Table II provides VPWM
values for typical duty cycles. See the âDuty Cycle vs
Voltageâ typical performance curve for additional duty cycle
values.
The Duty Cycle Adjust pin should not be driven below 0.1V.
If the voltage source used can go between 0.1V and ground,
a 1k⦠series resistor between the voltage source and the Duty
Cycle Adjust pin (Figure 5) is required to limit swing. If the
pin is driven below 0.1V, the output will be unpredictable.
DRV102
5
VS
PWM
VPWM 3
6
Gnd 4
1kâ¦(1)
Out
D/A
Converter
(or analog
voltage)
NOTE: (1) Required if voltage source can go below 0.1V.
FIGURE 5. Using a Voltage Source to Program Duty Cycle.
The DRV102âs internal 24kHz oscillator sets the PWM
1000
period. This frequency is not externally adjustable. Duty
Cycle Adjust (pin 3) is internally driven by a 200µA current
source and connects to the input of a comparator and a 19kâ¦
resistor as shown in Figure 6. The DRV102âs PWM control
100
design is inherently monotonic. That is, a decreased voltage
(or resistor value) always produces an increased duty cycle.
10
1
10
20
40
Duty Cycle (%)
60 80 100
RPWM = [ a + b (DC) + c (DC)2 + d (DC)3 + e (DC)4]â1
where: a = â4.9686 x 10â8
b = â5.9717 x 10â8
c = 2.9889 x 10â8
d = â5.4837 x 10â10
e = 5.9361 x 10â12
DC = duty cycle in %
For 50% duty cycle:
RPWM = [â4.9686 x 10â8 + (â5.9717 x 10â8) (50) + (2.9889 x 10â8) (50)2
+ (â5.4837 x 10â10) (50)3 + (5.9361 x 10â12) (50)4]â1
= 24.9kâ¦
3.8V
f = 24kHz
0.7V
Comparator
VS
200µA
DRV102
19kâ¦
3
Duty Cycle
Adjust
Resistor or
Voltage Source(1)
NOTE: (1) Do not drive pin below 0.1V.
FIGURE 4. RPWM versus Duty Cycle.
10
FIGURE 6. Simplified Circuit Model of the Duty Cycle
Adjust Pin.
DRV102
www.ti.com
SBVS009A
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