LTC6101HV Linear Technology, LTC6101HV Datasheet - Page 10

• Manufacturer Part Number: LTC6101HV
• Description: High-Side Current Sense Amplifier
• Manufacturer: Linear Technology

LTC6101/LTC6101HV
APPLICATIO S I FOR ATIO
10
Selection of External Input Resistor, R
The external input resistor, R
ductance of the current sense circuit. Since I
R
100, then I
100mV.
R
limiting the output current. At low supply voltage, I
be as much as 1mA. By setting R
expected sense voltage gives I
mum output dynamic range is available. Output dynamic
range is limited by both the maximum allowed output
current and the maximum allowed output voltage, as well
as the minimum practical output signal. If less dynamic
range is required, then R
reducing the max output current and power dissipation.
If low sense currents must be resolved accurately in a
system that has very wide dynamic range, a smaller R
the max current spec allows may be used if the max
current is limited in another way, such as with a Schottky
diode across R
IN
IN
, transconductance g
should be chosen to allow the required resolution while
V
OUT
OUT
I
LOAD
SENSE
= V
SENSE
CMPZ4697
301
4
2
U
(Figure 3a). This will reduce the high
10k
LTC6101
/100 or I
m
IN
+
R
U
SENSE LO
100m
= 1/R
can be increased accordingly,
–
IN
OUT
M1
Si4465
, controls the transcon-
IN
Figure 3b. Dual LTC6101s Allow High-Low Current Ranging
301
OUT
IN
3
5
1
. For example, if R
= 1mA, then the maxi-
W
such that the largest
V
= 1mA for V
IN
R
7.5k
5
IN
4
2
301
OUT
LTC6101
U
(
0 ≤ I
= V
V
LOGIC
+
OUT
R
SENSE
SENSE HI
LOAD
IN
SENSE
10m
–
+5V
than
may
IN
≤ 10A
)
=
=
≤ V
7.5k
/
301
3
5
1
IN
≤ 60V
This approach can be helpful in cases where occasional
large burst currents may be ignored. It can also be used in
a multirange configuration where a low current circuit is
added to a high current circuit (Figure 3b). Note that a
comparator (LTC1540) is used to select the range, and
transistor M1 limits the voltage across R
Care should be taken when designing the board layout for
R
nect impedances will increase the effective R
causing a gain error. In addition, internal device resistance
will add approximately 0.2Ω to R
Figure 3a. Shunt Diode Limits Maximum Input Voltage to Allow
Better Low Input Resolution Without Overranging
current measurement accuracy by limiting the result, while
increasing the low current measurement resolution.
V
IN,
IN
especially for small R
BAT54C
V
LOGIC
1.74M
619k
40.2k
HIGH CURRENT RANGE OUT
250mV/A
LOW CURRENT RANGE OUT
2.5V/A
3
4
5
6
(3.3V TO 5V)
R
+
–
SENSE
V
2
LOGIC
7
1
LTC1540
LOAD
V
+
IN
6101 F03a
(I
values. All trace and intercon-
INDICATOR
LOAD
8
RANGE
HIGH
> 1.2A)
D
IN
SENSE
6101 F03b
.
4.7k
SENSE LO
Q1
CMPT5551
IN
.
value,
6101fa