TS1101 TOUCHSTONE [Touchstone Semiconductor Inc], TS1101 Datasheet - Page 8

• Manufacturer Part Number: TS1101
• Description: A 1uA, +2V to +25V Bidirectional Precision Current-Sense Amplifier
• Manufacturer: TOUCHSTONE [Touchstone Semiconductor Inc]

GAIN (V/V)
TS1101
external V
gate of M1 such that M1’s drain-source current is
equal to:
or
Since M1’s drain terminal is connected to ROUT, the
output voltage of the TS1101 at the OUT terminal is,
therefore;
When the voltage at the RS- terminal is greater than
the voltage at the RS+ terminal, the external
VSENSE voltage drop is impressed upon RGAINB.
The voltage drop across RGAINB is then converted
into a current by M2 that then produces an output
voltage across ROUT. In this design, when M1 is
conducting current (V
internal amplifier holds M2 OFF. When M2 is
conducting current (V
amplifier holds M1 OFF. In either case, the disabled
FET does not contribute to the resultant output
voltage.
The current-sense amplifier’s gain accuracy is
therefore the ratio match of ROUT to RGAIN[A/B].
For each of the four gain options available, Table 1
lists the values for ROUT and RGAIN[A/B]. The
TS1101’s output stage is protected against input
overdrive by use of an output current-limiting circuit
of
circuit.
Table 1: Internal Gain Setting Resistors (Typical
The SIGN Comparator Output
As shown in the TS1101’s block diagram, the design
of the TS1101 incorporated one additional feature –
an analog comparator the inputs of which monitor
the internal amplifier’s differential output voltage.
While the voltage at the TS1101’s O T terminal
Page 8
3mA
100
200
25
50
(typical) and a
Values)
V
SENSE
O T
RGAIN[A/B] (Ω)
, op amp feedback action drives the
I
DS M1
I
LOAD
400
200
100
100
I
DS M1
x R
I
RS+
LOAD
7V
RS-
RGAINA
S NS
RGAINA
internal clamp protection
V
> V
x R
> V
S NS
ROUT (Ω)
S NS
x
10k
10k
10k
20k
RS-
RS+
RGAINA
, the TS1101’s
R
), the internal
O T
Part Number
TS1101-100
TS1101-200
TS1101-25
TS1101-50
indicates the magnitude of the load current, the
TS1101’s SIGN output indicates the load current’s
direction. The SIGN output is a logic high when M1
is conducting current (V
SIGN output is a logic low when M2 is conducting
current (V
transfer characteristic is illustrated in Figure 1.
Unlike other current-sense amplifiers that implement
a OUT/SIGN arrangement, the TS1101 exhibits no
“dead zone” at I
Figure 2: SIGN Comparator Propagation Delay vs V
Figure 1: TS1101's SIGN Comparator Transfer
100
0.1
10
1
0.1
RS+
Characteristic.
V
LOAD
< V
SENSE
switchover.
RS-
1
(│V
). The SIGN comparator’s
RS+
RS+
- V
> V
RS-
│) - mV
RS-
10
). Alternatively, the
TS1101DS r1p0
100
SENSE
RTFDS
.