DRV110_15 Datasheet, PDF (8/24 Pages) Texas Instruments – Power-Saving Solenoid Controller

DRV110
SLVSBA8B – MARCH 2012 – REVISED JULY 2015
Feature Description (continued)
I_SOLENOID
I_PEAK
www.ti.com
I_HOLD
t
t_KEEP
EN
t
Figure 2. Typical Current Waveform Through the Solenoid
t_KEEP is set externally by connecting a capacitor to the KEEP pin. A constant current is sourced from the KEEP
pin that is driven into an external capacitor resulting in a linear voltage ramp. When the KEEP pin voltage
reaches 100 mV, the current regulation reference voltage, V_REF, is switched from V_PEAK to V_HOLD. Dependency of
t_KEEP from the external capacitor size can be calculated by:
t_KEEP
éësùû
=
C_KEEP
éëFùû
× 10⁵
ésù
êë_F úû
(1)
The current control loop regulates, cycle-by-cycle, the solenoid current by sensing voltage at the SENSE pin and
controlling the external switching device gate through the OUT pin. During the ON-cycle, the OUT pin voltage is
driven and kept high (equal to VIN voltage) allowing current to flow through the external switch as long as the
voltage at the SENSE pin is less than V_REF. As soon as the voltage at the SENSE pin is above V_REF, the OUT
pin voltage is immediately driven and kept low until the next ON-cycle is triggered by the internal PWM clock
signal. In the beginning of each ON-cycle, the OUT pin voltage is driven and kept high for at least the time
determined by the minimum PWM signal duty cycle, D_MIN.
V_PEAK and V_HOLD depend on fixed resistance values R_PEAK and R_HOLD approximately as shown in Figure 3. If the
PEAK pin is connected to ground, the peak current reference voltage, V_PEAK, is at its default value (internal
setting). The V_PEAK value can alternatively be set by connecting an external resistor to ground from the PEAK
pin. For example, if a 50-kΩ (= R_PEAK) resistor is connected between PEAK and GND, and R_SENSE = 1 Ω, then
the externally set I_PEAK level will be 900 mA. If R_PEAK = 200 kΩ and R_SENSE = 1 Ω, then the externally set I_PEAK
level will be 300 mA. In case R_SENSE = 2 Ω instead of 1 Ω, then I_PEAK = 450 mA (when R_PEAK = 50 kΩ) and
I_PEAK = 150 mA (when R_PEAK = 200 kΩ). In the 8-pin package, the HOLD reference uses the internal V_REF setting
of 50 mV. In the 14-pin package, external setting of the HOLD current, I_HOLD, works in the way as the external
setting for I_PEAK but the current levels are 1/6 of the I_PEAK levels. External settings for I_PEAK and I_HOLD are
independent of each other. If R_PEAK or R_HOLD is decreased below 33.33 kΩ (typical value), then the reference is
clamped to the internal setting of 300 mV for PEAK and 50 mV for HOLD. Approximate I_PEAK and I_HOLD values
can be calculated by using the formula below.
I_PEAK
= ^VREF
R_SENSE
=
1W
´
900 mA ´ 66.67
R_PEAK
kW
´
1
R_SENSE
;
66.67
kW
<
R_PEAK
< 2 MW
(2)
I_HOLD
= ^VREF
R_SENSE
=
1W
´150 mA ´ 66.67
R_HOLD
kW
´
1
R_SENSE
;
66.67
kW
<
R_HOLD
< 2 MW
(3)
8
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