DRV411_15 Datasheet, PDF (19/34 Pages) Texas Instruments – Sensor Signal Conditioning IC for Closed-Loop Magnetic Current Sensors

DRV411
www.ti.com
SBOS693B – AUGUST 2013 – REVISED DECEMBER 2013
VOLTAGE REFERENCE
The precision reference circuit offers low drift (typically 5 ppm/K) and is used for internal biasing; it is also
connected to the REFOUT pin. The circuit is intended as the reference point of the output signal to allow a
bipolar signal around it. This output is buffered for low impedance and tolerates sink and source currents of ±5
mA. Capacitive loads can be directly connected, but generate ringing on fast load transients. A small series
resistor of a few ohms improves the response, especially for a capacitive load in the range of 1 μF.
Reference Output Voltage Selection
As shown in Table 2, the most common use-cases for the DRV411 are with 5-V and 3.3-V power supplies, where
the sensor output must be centered at 2.5 V and 1.65 V, respectively. The internal reference provides very good
accuracy and drift performance. See the Electrical Characteristics for detailed information.
Table 2. Reference Output Voltage Selection
MODE
REF = 2.5 V
REF = 1.65 V
Ratiometric output
REFSEL1
0
1
1
REFSEL2
0
0
1
DESCRIPTION
Used with sensor module supply of 5 V
Used with sensor module supply of 3.3 V
Provides output centered on V_S / 2
In the ratiometric output mode, the reference is bypassed and the power supply is divided by two. The internal
resistor divider offers very tight tolerances and a temperature coefficient of less than 10 ppm/°C. In this case, the
sensor module output is centered on V_S / 2.
For sensor modules with a reference pin, the DRV411 also allows overwriting the internal reference with an
external reference voltage, as shown in Figure 53. When an external reference that has a significant voltage
difference compared to the internal reference is connected, resistor R₅ limits the current flowing from the internal
reference. In this case, the internal reference sources the current shown in Equation 2:
I_{int_ref}
=
V_{int_ref}  V_{ext_ref}
600 :
(2)
Compensation
Coil
Current Sense Module
VDD
IAIN1
R1
10 k 
R2
40 k 
DRV411
RSHUNT
IAIN2
R3
10 k 
_
Differential
Amplifier
+
R4
40 k 
ICOMP
Internal
Voltage
Reference
VOUT
REFIN
R5
Dummy Shunt
(optional)
REFOUT
R6
600 
REFIN
(external)
External
Voltage
Reference
GND
Figure 53. DRV411 with External Reference
The example of 600 Ω for R6 was chosen for illustration purposes; different values are possible. Note that if no
external reference is connected, R6 has little impact on the common-mode rejection of the differential amplifier,
and therefore, should be as small as possible.
Copyright © 2013, Texas Instruments Incorporated
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