DRV401-Q1 Datasheet, PDF (26/39 Pages) Texas Instruments – DRV401-Q1 Sensor Signal Conditioning Device for Closed-Loop Magnetic Current Sensor

DRV401-Q1
SBOS814 – DECEMBER 2016
www.ti.com
Application Information (continued)
• R₅ is the dummy shunt (R_D) resistor used to restore the symmetry of both differential amplifier inputs. R₅ = 4
× R_SHUNT, but the accuracy is less important.
• R₆ and R₇ are pull-up resistors connected to the logic outputs.
• C₁ and C₂ are decoupling capacitors. Use low ESR-type capacitors connected close to the pins. Use low-
impedance printed circuit board (PCB) traces, either avoiding vias (plated-through holes) or using multiple
vias. A combination of a large (> 1-μF) and a small (< 4.7-nF) capacitor are suggested. When selecting
capacitors, make sure to consider the large pulse currents handled from the DRV401-Q1 device.
• D₁ and D₂ are protection diodes for the differential amplifier input. They are only needed if the voltage drop at
R_SHUNT exceeds 10 V at the maximum possible peak current.
8.2 Typical Application
The differential (H-bridge) driver arrangement for the compensation coil requires a differential sense amplifier for
the shunt voltage. This differential amplifier offers wide bandwidth and a high slew rate for fast current sensors.
Excellent dc stability and accuracy result from an auto-zero technique. The voltage gain is 4 V/V, set by precisely
matched and stable internal SiCr resistors.
Both inputs of the differential amplifier are normally connected to the current shunt resistor. The resistor adds to
the internal (10-kΩ) resistor, slightly reducing the gain in this leg. For best common-mode rejection (CMR), a
dummy shunt resistor (R₅) is placed in series with the REF_IN pin to restore matching of both resistor dividers, as
shown in Figure 43.
I_COMP2
DRV401-Q1
Differential Amplifier Section
R₁
10 kW
R₂
40 kW
Decoupling, Low-Pass Filter
R_SHUNT
R₃
10 kW
Differential
Amplifier
R₄
40 kW
V_OUT
R_F
50 W
REF_IN
R₅
Dummy
Shunt
C_F
10 nF
ADC
Compensated
REF_IN
K2
Copyright © 2016, Texas Instruments Incorporated
R₅ is a dummy shunt resistor equal to 4 × R_SHUNT to compensate for R_SHUNT and provide optimal CMR.
Figure 43. Internal Difference Amplifier with an Example of a Decoupling Filter
8.2.1 Design Requirements
• Operate from a single 5-V power supply.
• Measure the compensation coil current with a gain = 4 V/V.
• Maximize the gain accuracy.
• Minimize the common-mode error.
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