Datasheet

DRV104
9
SBVS036B
www.ti.com
DUTY CYCLE R
PWM
(Ω) (Nearest 1% Values)
(%)
5kHz 25kHz 100kHz
10 412k 84.5k 25.5k
20 487k 97.6k 28.7k
30 562k 113k 31.6k
40 649k 130k 35.7k
50 715k 147k 39.2k
60 787k 162k 43.2k
70 887k 174k 44.9k
80 953k 191k —
90 1050k 205k —
FIGURE 6. Using a Resistor to Program Duty Cycle.
FIGURE 5. Output Waveform at High Load Current.
FIGURE 7. Using a Voltage to Program Duty Cycle.
DUTY CYCLE V
PWM
(%) (V)
10 1.501
20 1.773
40 2.296
60 2.813
80 3.337
90 3.589
TABLE IV. Duty Cycle Adjust Voltage.
TABLE III. Duty Cycle Adjust Resistance.
ADJUSTABLE DUTY CYCLE (PWM MODE)
The DRV104’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 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 DRV104 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 Duty Cycle Adjust (pin 1) and ground. High
resistor values correspond to high duty cycles. At 100kHz,
the range of adjustable duty cycle is limited to 10% to 70%.
Table III provides resistor values for typical duty cycles.
Resistor values for additional duty cycles can be obtained
from Figure 6.
Voltage Controlled Duty Cycle
The duty cycle can also be programmed by analog voltage
V
PWM
. With V
PWM
≈ 3.59V, the duty cycle is about 90%.
Decreasing this voltage results in decreased duty cycles. Table
IV provides V
PWM
values for typical duty cycles. Figure 7 shows
the relationship of duty cycle versus V
PWM
and its linearity.
10M
1M
100k
10k
20 400
R
PWM
(Ω)
60 80 100
DUTY CYCLE vs R
PWM
Duty Cycle (%)
5kHz
25kHz
100kHz
R
PWM
(kΩ) = 334.35 + 7.75(%DC)
R
PWM
(kΩ) = 68.73 + 1.52(%DC)
R
PWM
(kΩ) = 20.62 + 0.39(%DC)
R
FREQ
only
With
100pF in
Parallel
with R
FREQ
Time (10µs)
100
90
80
70
60
50
40
30
20
10
0
21
Duty Cycle (%)
2.0
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
Duty Cycle Error (%)
34
DUTY CYCLE AND DUTY CYCLE ERROR
vs VOLTAGE
V
PWM
(V)
Duty Cycle
Duty Cycle Error
At V
S
= 24V and F = 25kHz: V
PWM
= 1.25 + 0.026 × %DC