TS1103 TOUCHSTONE [Touchstone Semiconductor Inc], TS1103 Datasheet - Page 8

• Manufacturer Part Number: TS1103
• Description: A 1?A, 200?VOS Bidirectional Precision Current-Sense Amplifier
• Manufacturer: TOUCHSTONE [Touchstone Semiconductor Inc]

GAIN (V/V)
TS1103
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 TS1103 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
TS1103’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 S1103’s block diagram, the design
of the TS1103 incorporated one additional feature –
an analog comparator the inputs of which monitor
the internal amplifier’s differential output voltage.
While the voltage at the TS1103’s
Page 8
3mA
100
200
25
50
(typical) and a
Values)
V
SENSE
RGAIN[A/B] (Ω)
, op amp feedback action drives the
DS M1
L AD
400
200
100
100
DS M1
x R
RS+
L AD
7V
RS-
R A A
SE SE
R A A
internal clamp protection
V
> V
x R
> V
SE SE
ROUT (Ω)
SE SE
x
10k
10k
10k
20k
RS-
RS+
R A A
), the TS1103’s
R
), the internal
terminal
Part Number
TS1103-100
TS1103-200
TS1103-25
TS1103-50
indicates the magnitude of the load current, the
TS1103’s 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 TS1103 exhibits no
“dead zone” at
Figure 2: SIGN Comparator Propagation Delay vs V
Figure 1: TS1103's SIGN Comparator Transfer
100
0.1
10
1
0.1
Characteristic.
RS+
V
LOAD
SENSE
< V
output indicates the load current’s
1
(│V
switchover.
RS-
RS+
).
RS+
- V
> V
he S
RS-
│) - mV
10
RS-
). Alternatively, the
TS1103DS r1p0
comparator’s
100
SENSE
.
RTFDS