DRV401-Q1 Datasheet, PDF (29/39 Pages) Texas Instruments – DRV401-Q1 Sensor Signal Conditioning Device for Closed-Loop Magnetic Current Sensor

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DRV401-Q1
SBOS814 – DECEMBER 2016
V(DEMAG)
1
V(ERROR)
4
V(I_COMP2)
2
R_SH = 10 W
3.4 ms
V_OUT
3
500 ms/div
The ERROR flag resets to H (as shown) and the output settles back to normal operation.
Figure 49. Demagnetization and Power-On Timing: Abort of Demagnetization Cycle
10 Layout
10.1 Layout Guidelines
The typical device configuration is shown in Figure 42. The DRV401-Q1 operates with relatively large currents
and fast current pulses, and offers wide-bandwidth performance. The device is often exposed to large distortion
energy from the primary signal and the operating environment. Therefore, the wiring layout must provide
shielding and low-impedance connections between critical points.
Use low-ESR capacitors for power-supply decoupling. Use a combination of a small capacitor and a large
capacitor with a 1-μF or larger value. Use low-impedance tracks to connect the capacitors to the pins.
Both grounds must be connected to a local ground plane. Both supplies can be connected together; however,
best results are achieved with separate decoupling (to the local GND plane) and ferrite beads in series with the
main supply. The ferrite beads decouple the DRV401-Q1 device, reducing interaction with other circuits powered
from the same supply voltage source.
The reference output is referred to GND2. A low-impedance, star-type connection is required to avoid the driver
current and the probe current modulating the voltage drop on the ground track.
The connection wires of the difference amplifier to the shunt must be low resistance and of equal length. For best
accuracy, avoid current in this connection. Consider using a Kelvin Contact-type connection. The required
resistance value may be set using two resistors.
Wires and PCB traces for S1 and S2 must be close or twisted. I_COMP1 and I_COMP2 must be wired close together.
To avoid capacitive coupling, run a ground shield between the S1/S2 and I_COMP wire pair or keep them distant
from each other.
The compensation driver outputs (I_COMP) are low frequency only. However, the primary signal (with high-
frequency content present) is coupled into the compensation winding, the shunt, and the difference amplifier. TI
recommends a careful layout.
The REF_OUT and V_OUT output drives some capacitive loads, but avoid large direct capacitive loads; these loads
increase internal pulse currents. Given the wide bandwidth of the differential amplifier, isolate any large
capacitive load with a small series resistor. A small capacitor (in the pF range) improves the transient response
on a high resistive load.
The exposed thermal pad on the bottom of the package must be soldered to GND because the thermal pad is
internally connected to the substrate, which must be connected to the most negative potential. Solder the
exposed pad to the PCB to provide structural integrity and long-term reliability.
Copyright © 2016, Texas Instruments Incorporated
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