VDD
REFOUT
VR1
4
-
=
OUT
OUT
shunt
V
V
B
G x Gfg x R
4 x 12.2 x R1
=
=
EVM Operation
4
EVM Operation
Factory setup of the DRV425EVM is for an input supply voltage range from 3.3 V to 5 V. Resistors R3
through R8 configure the reference voltage and bandwidth settings of the DRV425EVM. The default
conditions are listed in
.
Table 2. Factory Configuration Defaults
RESISTOR
FUNCTION
DEFAULT CONDITION
R3
Pull-up for RSEL0 to VDD
0
Ω
R4
Pull-down for RSEL0 to GND
open
R5
Pull-up for RSEL1 to VDD
0
Ω
R6
Pull-down for RSEL1 to GND
open
R7
Pull-up for BSEL to VDD
0
Ω
R8
Pull-down for BSEL to GND
open
If the default condition is not the desired configuration of the DRV425EVM, simply remove and replace the
resistors for the desired operating mode. If there is a desire to modify the state of the reference voltage or
device bandwidth during physical operation of the EVM, resistors R3 through R8 can be removed and
driven directly via GPIO pins on a microprocessor using fly wires.
4.1
Error and Over Range
R2 and R9 are 10-k
Ω
pull-up resistors on the Over Range (/OR) and Error (/ER) flag output pins
respectively. To observe the state of the flags, simply probe the chip side of the resistor. These outputs
are open drain and a pull up is required to observe the active low output state. These pins may also be fly-
wired to a micro controller for use as interrupt pins.
4.2
Calculation of Magnetic Field Strength
The magnetic field strength (B) can be calculated by
.
(1)
The maximum magnetic field range of the DRV425 is ±2 mT. With the 100
Ω
shunt located at R1, the
maximum field measurement range is ±500 µT.To increase the sensitivity, R1 can be adjusted based on
. Higher magnetic fields result in increased current flowing through R1. The output voltage of
the differential amplifier in the DRV425 will reach its peak amplitude with a maximum voltage drop across
R1 as shown in
.
(2)
4
DRV425 Evaluation Module
SLOU410A – September 2015 – Revised October 2015
Copyright © 2015, Texas Instruments Incorporated
