Datasheet

DRV103
9
SBVS029A
A 100pF capacitor in parallel with R
PWM
is recommended
when switching a high load current to maintain a clean
output switching waveform, as shown in Figure 6.
The DRV103’s adjustable PWM output frequency allows it
to be optimized for driving virtually any type of load.
ADJUSTABLE DUTY CYCLE (PWM Mode)
The DRV103’s externally adjustable duty cycle provides an
accurate means of controlling power delivered to a load.
Duty cycle can be set over a range of at least 10% to 90%
with an external resistor, analog voltage, or the voltage
output of a D/A converter. A low duty cycle results in
reduced power dissipation in the load. This keeps the DRV103
and the load cooler, resulting in increased reliability for both
devices.
Resistor Controlled Duty Cycle
Duty cycle is easily programmed by connecting a resistor
(R
PWM
) between the Duty Cycle Adjust pin (pin 1) and
ground. High resistor values correspond to high duty cycles.
Table III provides resistor values for typical duty cycles.
Resistor values for additional duty cycles can be obtained
from Figure 5. For reference purposes, the equation for
calculating R
PWM
is included in Figure 5.
DUTY CYCLE R
PWM
(Nearest 1% Values)
(%)
5kHz 25kHz 100kHz
5 374k 75k 16.9k
10 402k 80.6k 19.1k
20 475k 95.3k 22.6k
30 549k 110k 26.1k
40 619k 124k 29.4k
50 681k 137k 33.2k
60 750k 150k 37.4k
70 825k 165k 40.2k
80 887k 182k 44.2k
90 953k 196k 47.5k
95 1M 200k 49.9k
TABLE III. Duty Cycle Adjust Resistance.
FIGURE 5. Using a Resistor to Program Duty Cycle.
At 25kHz: R
PWM
(kΩ) = 67.46 + 1.41 • %DC.
1M
100k
10k
20 400
R
PWM
(Ω)
60 80 100
DUTY CYCLE vs R
PWM
Duty Cycle (%)
5kHz
25kHz
100kHz
R
PWM
only on
Pin 1
With
100pF in
Parallel with
R
PWM
Time (10µs)
FIGURE 6. Output Waveform at High Load Current.
100
90
80
70
60
50
40
30
20
10
0
21
Duty Cycle (%)
2
1.5
1
0.5
0
–0.5
–1
–1.5
–2
Duty Cycle Error (%)
34
DUTY CYCLE AND DUTY CYCLE ERROR
vs VOLTAGE
V
PWM
(V)
FIGURE 7. Using a Voltage to Program Duty Cycle.
At V
S
= 24V and F = 25kHz: V
PWM
= 1.25 +
0.026 • %DC.
Voltage Controlled Duty Cycle
Duty cycle can also be programmed by an analog voltage,
V
PWM
. With V
PWM
≈ 3.56V, duty cycle is about 90%.
Decreasing this voltage results in decreased duty cycles.
Table IV provides V
PWM
values for typical duty cycles. The
“Duty Cycle vs Voltage” typical performance curve for
additional duty cycles is shown in Figure 7.
DUTY CYLE V
PWM
(%) (V)
5 1.344
10 1.518
20 1.763
40 2.283
60 2.788
80 3.311
90 3.561
95 3.705
TABLE IV. Duty Cycle Adjust Voltage.