TS1103 TOUCHSTONE [Touchstone Semiconductor Inc], TS1103 Datasheet - Page 9

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

behavior is its propagation delay as a function of
applied V
shown
APPLICATIONS INFORMATION
Choosing the Sense Resistor
Selecting the optimal value for the external RSENSE
is based on the following criteria and for each
commentary follows:
1) RSENSE Voltage Loss
For lowest IR power dissipation in RSENSE, the
smallest usable resistor value for RSENSE should
be selected.
2) V
and Desired V
As there is no separate power supply pin for the
TS1103, the circuit draws its power from the voltage
at its RS+ and RS- terminals. Therefore, the signal
voltage at the OUT terminal is bounded by the
minimum voltage applied at the RS+ terminal.
Therefore,
and
where the full-scale V
V
terminal voltage. For best performance with a 3.6V
power supply, RSENSE should be chosen to
generate a V
option), b) 60mV (for the 50V/V GAIN option), c)
30mV (for the 100V/V GAIN option), or d) 15mV (for
the 200V/V GAIN option) at the full-scale I
current in each application. For the case where the
TS1103DS r1p0
he other attribute of the S
OUT(MAX)
1) RSENSE Voltage Loss
2) V
3) Total I
4) Circuit Efficiency and Power Dissipation
5) RSENSE Kelvin Connections
OUT
V
OUT(max)
Swing vs. Applied Input Voltage at V
and Desired V
/ A
in
OUT
SENSE
R
SENSE
Figure
SE SE
Swing vs. Applied Input Voltage at V
LOAD
= V
SENSE
[(V
at the application’s minimum RS+
RS+(min)
of: a) 120mV (for the 25V/V GAIN
RS+
Accuracy
SENSE
,
- V
A
SENSE
- V
V
the
RS-
SENSE(max)
) or (V
L AD
should be less than
S
max
max
RS-
– V
comparator’s
comparator’s
- V
OH(max)
RS+
RS+
)]. As
LOAD
RS+
propagation delay behavior is symmetric regardless
of current-flow direction and is inversely proportional
to V
minimum power supply voltage is higher than 3.6V,
each of the four full-scale V
increased.
3) Total Load Current Accuracy
In
V
to the circuit’s accuracy: a the TS1103’s input offset
voltage (V
(GE(max) = 0.6%). An expression for the TS1103’s
total error is given by:
A large value for RSENSE permits the use of smaller
load currents to be measured more accurately
because the effects of offset voltages are less
significant when compared to larger VSENSE
voltages. Due care though should be exercised as
previously mentioned with large values of RSENSE.
4) Circuit Efficiency and Power Dissipation
IR losses in RSENSE can be large especially at high
load currents. It is important to select the smallest,
usable RSENSE value to minimize power dissipation
and to keep the physical size of RSENSE small. If
the external RSENSE is allowed to dissipate
significant power, then its inherent temperature
coefficient may alter its design center value, thereby
reducing load current
Precisely because the TS1103’s input stage was
designed to exhibit a very low input offset voltage,
small RSENSE values can be used to reduce power
dissipation and minimize local hot spots on the pcb.
5) RSENSE Kelvin Connections
For optimal V
load currents, parasitic pcb track resistance should
be
between RSENSE and the TS1103’s RS+ and RS-
terminals are strongly recommended. The drawing in
Figure 3 illustrates the connections between the
OUT
V
OUT
SENSE
minimized.
< V
the
= [GAIN x (1 ± GE) x V
.
OUT(max)
OS(max)
TS1103’s
SENSE
, there are two specifications related
= 200μV) and b) its gain error
Kelvin-sense
accuracy in the presence of large
linear
measurement
SENSE
SENSE
TS1103
pcb
] ± (GAIN x V
s above can be
region
connections
accuracy.
Page 9
where
RTFDS
OS
)