INA203 Datasheet, PDF (13/25 Pages) Burr-Brown (TI) – Unidirectional Measurement Current-Shunt Monitor with Dual Comparators

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TRANSIENT PROTECTION
The –16V to +80V common-mode range of the
INA203, INA204, and INA205 is ideal for
withstanding automotive fault conditions ranging from
12V battery reversal up to +80V transients, since no
additional protective components are needed up to
those levels. In the event that the INA203, INA204,
and INA205 are exposed to transients on the inputs
in excess of their ratings, then external transient
absorption with semiconductor transient absorbers
(zeners or Transzorbs) are necessary. Use of metal
oxide varistors (MOVs) or video disk recorders
(VDRs) is not recommended except when they are
used in addition to a semiconductor transient
absorber. Select the transient absorber such that it
will never allow the INA203, INA204, and INA205 to
be exposed to transients greater than +80V (that is,
allow for transient absorber tolerance, as well as
additional voltage because of transient absorber
dynamic impedance). Despite the use of internal
zener-type ESD protection, the INA203, INA204, and
INA205 do not lend themselves to using external
resistors in series with the inputs because the
internal gain resistors can vary up to ±30% but are
closely matched. (If gain accuracy is not important,
then resistors can be added in series with the
INA203, INA204, and INA205 inputs with two equal
resistors on each input.)
OUTPUT VOLTAGE RANGE
The output of the INA203, INA204, and INA205 is
accurate within the output voltage swing range set by
the power-supply pin, V+. This performance is best
INA203
INA204
INA205
SBOS393 – MARCH 2007
illustrated when using the INA205 (a gain of 100
version), where a 100mV full-scale input from the
shunt resistor requires an output voltage swing of
+10V, and a power-supply voltage sufficient to
achieve +10V on the output.
INPUT FILTERING
An obvious and straightforward location for filtering is
at the output of the INA203, INA204, and INA205
series; however, this location negates the advantage
of the low output impedance of the internal buffer.
The only other option for filtering is at the input pins
of the INA203, INA204, and INA205, which is
complicated by the internal 5kΩ + 30% input
impedance; this configuration is illustrated in
Figure 33. Using the lowest possible resistor values
minimizes both the initial shift in gain and effects of
tolerance. The effect on initial gain is given by
Equation 3:
Gain Error % = 100 - 100 ´ ^5kW
5kW + R_FILT
(3)
Total effect on gain error can be calculated by
replacing the 5kΩ term with 5kΩ – 30%, (or 3.5kΩ)
or 5kΩ + 30% (or 6.5kΩ). The tolerance extremes of
R_FILT can also be inserted into the equation. If a pair
of 100Ω 1% resistors are used on the inputs, the
initial gain error will be 1.96%. Worst-case tolerance
conditions will always occur at the lower excursion of
the internal 5kΩ resistor (3.5kΩ), and the higher
excursion of R_FILT – 3% in this case.
V_S 1
OUT 2
CMP1 IN-/0.6V REF 3
CMP1 IN+ 4
CMP2 IN+ 5
CMP2 IN-/0.6V REF 6
GND 7
V_SUPPLY
R_SHUNT << R_FILTER
3mW
Load
INA203-INA205
1.2V REF
R_FILTER < 100W
V_IN+
14
V_IN-
13
C_FILTER
12 1.2V REF OUT
R_FILTER <100W
11 CMP1 OUT
10 CMP2 OUT
9 CMP2 DELAY
8 CMP1 RESET
f_-3dB
f_-3dB =
1
2p(2R_FILTER)C_FILTER
SO-14, TSSOP-14
Figure 33. Input Filter (Gain Error: 1.5% to –2.2%)
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