TS1102
low-pass filters in series with the current-sense
amplifier’s inputs only introduces additional offset
voltage and gain errors. To minimize or eliminate
altogether the need for external low-pass filters and
to maintain low input offset voltage and gain errors,
the TS1102 incorporates a 50-kHz (typ), 2nd-order
differential low-pass filter as shown in the TS1102’s
Block Diagram.
the RS+ and the RS- input terminals of the TS1102
should be short and symmetric. Also recommended
are a ground plane and surface mount resistors and
capacitors.
Using the TS1102 in Bidirectional Load Current
Applications
In many battery-powered systems, it is oftentimes
necessary to monitor a battery’s discharge and
Optional Output Filter Capacitor
charge currents. To perform this function,
a
bidirectional current-sense amplifier is required. The
circuit illustrated in Figure 2 shows how two
TS1102s can be configured as a bidirectional
current-sense amplifier. As shown in the figure, the
RS+/RS- input pair of TS1102 #2 is wired opposite
in polarity with respect to the RS+/RS- connections
of TS1102 #1. Current-sense amplifier #1 therefore
measures the discharge current and current-sense
amplifier #2 measures the charge current. Note that
both output voltages are measured with respect to
GND. When the discharge current is being
measured, VOUT1 is active and VOUT2 is zero; for the
case where charge current is being measured, VOUT1
is zero, and VOUT2 is active.
If the TS1102 is part of a signal acquisition system
where its OUT terminal is connected to the input of
an ADC with an internal, switched-capacitor track-
and-hold circuit, the internal track-and-hold’s
sampling capacitor can cause voltage droop at VOUT
.
A 22nF to 100nF good-quality ceramic capacitor
from the OUT terminal to GND forms a low-pass
filters with the TS1102’s ROUT and should be used to
minimize voltage droop (holding VOUT constant
during the sample interval. Using a capacitor on the
OUT terminal will also reduce the TS1102’s small-
signal bandwidth as well as band-limiting amplifier
noise.
PC Board Layout and Power-Supply Bypassing
For optimal circuit performance, the TS1102 should
be in very close proximity to the external current-
sense resistor and the pcb tracks from RSENSE to
Figure 2: Using Two TS1102s for Bidirectional Load Current Detection
Page 10
TS1102DS r1p0
RTFDS
TOUCHSTONE [ TOUCHSTONE SEMICONDUCTOR INC ]
