Datasheet

DRV104
8
SBVS036B
www.ti.com
INITIAL CONSTANT
OUTPUT DURATION C
D
3µs Pin 2 Tied to +5V
18µs Pin 2 Open
81µs 100pF
0.81ms 1nF
8.1ms 10nF
81ms 100nF
0.81s 1µF
8.1s 10µF
TABLE I. Delay Adjust Times.
FIGURE 3. Simplified Delay Adjust and Frequency Adjust Inputs.
FIGURE 4. Using a Resistor to Program Oscillator Frequency.
OSCILLATOR FREQUENCY R
FREQ
(nearest 1% values)
(Hz) (Ω)
100k 47.5k
50k 100k
25k 191k
10k 499k
5k 976M
500 10M
TABLE II. Oscillator Frequency Resistance.
APPLICATIONS INFORMATION
POWER SUPPLY
The DRV104 operates from a single +8V to +32V supply with
excellent performance. Most behavior remains unchanged
throughout the full operating voltage range. Parameters that
vary significantly with operating voltage are shown in the
Typical Characteristics.
ADJUSTABLE DELAY TIME
(INITIAL 100% DUTY CYCLE)
A unique feature of the DRV104 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 con-
nected from Delay Adjust (pin 2) to ground according to
Equation 1:
Delay Time ≈ (C
D
• 10
6
)/1.24 (1)
(time in seconds, C
D
in Farads)
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 3µs by connecting the pin to 5V.
Table I provides examples of delay times (constant output
before PWM mode) achieved with selected capacitor values.
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 DRV104 PWM output frequency can be easily pro-
grammed over a wide range by connecting a resistor (R
FREQ
)
between Osc Freq Adj (pin 3) and ground. A range of 500Hz
to 100kHz can be achieved with practical resistor values, as
shown in Table II. Refer to the PWM Frequency vs R
FREQ
plot
shown in Figure 4 for additional information. Although oscilla-
tor frequency operation below 500Hz is possible, resistors
higher than 10MΩ will be required. The pin becomes a very
high impedance node and is therefore sensitive to noise
3µA
C
D
R
FREQ
V
REF
I
REF
+V
S
V
REF
Reset
+2.6V
+1.25V
Input
1000M
100M
10M
1M
100k
10k
1k
100 1k10
R
FREQ
(Ω)
10k 100k 1M
PWM FREQUENCY vs R
FREQ
Frequency (Hz)
R
FREQ
kΩ () =
1
1.4518 × 10
−6
+ 2.0593 ×10
−7
× FHz
()
When switching a high-load current, 100pF capacitors in
parallel with R
FREQ
are recommended to maintain a clean
output switching waveform and duty cycle, see Figure 5.
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.
The DRV104’s adjustable PWM output frequency allows it to
be optimized for driving virtually any type of load.