Datasheet

DRV103
8
SBVS029A
The internal Delay Adjust circuitry is composed of a 3µA
current source and a 2.6V comparator, as shown in Figure 3.
Thus, when the pin voltage is less than 2.6V, the output
device is 100% ON (DC output mode).
OSCILLATOR FREQUENCY ADJUST
The DRV103 PWM output frequency can be easily pro-
grammed over a wide range by connecting a resistor (R
FREQ
)
between the Osc Freq Adj pin (pin 3) and ground. A range of
500Hz to 100kHz can be achieved with practical resistor
values, as shown in Table II. Refer to “PWM Frequency vs
R
FREQ
” typical performance curve shown in Figure 4 for
additional information. Although oscillator frequency opera-
tion below 500Hz is possible, resistors higher than 10M will
be required. The pin becomes a very high impedance node and
is, therefore, sensitive to noise pickup and PCB leakage
currents if very high resistor values are used. Refer to Figure
3 for a simplified circuit of the frequency adjust input.
APPLICATIONS INFORMATION
POWER SUPPLY
The DRV103 operates from a single +8V to +32V supply
with excellent performance. Most behavior remains un-
changed throughout the full operating voltage range. Param-
eters that vary significantly with operating voltage are shown
in the Typical Performance Curves. The DRV103 supply
voltage should be ≥ the supply voltage on the load.
ADJUSTABLE DELAY TIME (INITIAL 100% DUTY CYCLE)
A unique feature of the DRV103 is its ability to provide an
initial constant DC output (100% duty cycle) and then
switch to PWM mode output to save power. This function is
particularly useful when driving solenoids that have a much
higher pull-in current requirement than continuous hold
requirement.
The duration of this constant DC output (before PWM
output begins) can be externally controlled by a capacitor
connected from Delay Adjust (pin 2) to ground according to
the following equation:
Delay Time ≈ C
D
• 10
6
(time in seconds, C
D
in Farads • 1.1)
Leaving the Delay Adjust pin open results in a constant
output time of approximately 18µs. The duration of this
initial output can be reduced to less than 1µs by connecting
the pin to 5V. Table I provides examples of delay times
(constant output before PWM mode) achieved with selected
capacitor values.
INITIAL CONSTANT
OUTPUT DURATION C
D
1µs Pin 2 Tied to +5V
18µs Pin 2 Open
110µs 100pF
1.1ms 1nF
11ms 10nF
110ms 100nF
1.1s 1µF
11s 10µF
TABLE I. Delay Adjust Times.
FIGURE 3. Simplified Delay Adjust and Frequency Adjust Inputs.
3µA
C
D
R
FREQ
V
FREQ
I
REF
+V
S
V
REF
Reset
+2.6V
+1.3V
Input
1000M
100M
10M
1M
100k
10k
1k
100 1k10
R
FREQ
(Ω)
10k 100k 1M
PWM FREQUENCY vs R
FREQ
Frequency (Hz)
FIGURE 4. Using a Resistor to Program Oscillator Frequency.
R
FREQ
(kΩ) = 6808417/F
(1.0288)
OSCILLATOR FREQUENCY R
FREQ
(nearest 1% values)
(Hz) (Ω)
100k 47.5k
50k 100k
25k 205k
10k 523k
5k 1.07M
500 11.3M
TABLE II. Oscillator Frequency Resistance.