DRV401-EP Datasheet, PDF (19/33 Pages) Texas Instruments – SENSOR SIGNAL CONDITIONING IC FOR CLOSED-LOOP MAGNETIC CURRENT SENSOR

DRV401-EP
www.ti.com............................................................................................................................................................................................... SBVS104 – JANUARY 2008
I_COMP2
DRV401 Differential Amplifier Section
R₁
10kΩ
R₂
40kΩ
Decoupling, Low−Pass Filter
R_SHUNT
R₃
10kΩ
Differential
Amplifier
R₄
40kΩ
V_OUT
R_F
50Ω
REF_IN
R₅
Dummy
Shunt
C_F
10nF
ADC
Compensated
REF_IN
K2 ^{NOTE: R5 is a dummy shunt resistor equal to 4x RSHUNT to compensate for RSHUNT and provide best CMR.}
a) Internal difference amplifier with an example of a decoupling filter.
10µs/div
b) V_OUT of Figure 5a with R₅ = 20Ω and C_D = 100nF.
10µs/div
c) V_OUT of Figure 5a with R₅ = 50Ω and C_D = 10nF.
Figure 5. Internal Difference Amplifier With Example of a Decoupling Filter
OVER-RANGE COMPARATOR
High peak current can overload the differential amplifier connected to the shunt. The OVER-RANGE pin, an
open-drain output, indicates an over-voltage condition for the differential amplifier by pulling low. The output of
this flag is suppressed for 3 µs, preventing unwanted triggering from transients and noise. This pin returns to
high as soon as the overload condition is removed (external pull-up required to return the pin high).
This ERROR flag not only provides a warning about a signal clipping condition, but is also a window comparator
output for actively shutting off circuits in the system. The value of the shunt resistor defines the operating window
for the current. It sets the ratio between the nominal signal and the trip level of the Over-Range flag. The trip
current of this window comparator is calculated using the following example:
With a 5 V supply, the output voltage swing is approximately ±2.45 V (load and supply
voltage-dependent).
The gain of 4 V/V allows an input swing of ±0.6125 V.
Thus, the clipping current is I_MAX = 0.6125 V/R_SHUNT.
See the differential amplifier curve of the Typical Characteristics, Output Voltage vs Output Current.
The over-range condition is internally detected as soon as the amplifier exceeds its linear operating range, not
just a set voltage level. Therefore, the error or the over-range comparator level is reliably indicated in fault
conditions such as output shorts, low load or low supply conditions. As soon as the output cannot drive the
voltage higher, the flag is activated. This configuration is a safety improvement over a voltage level comparator.
Copyright © 2008, Texas Instruments Incorporated
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