LT6109IMS-1#TRPBF Linear Technology, LT6109IMS-1#TRPBF Datasheet - Page 21

• Manufacturer Part Number: LT6109IMS-1#TRPBF
• Manufacturer: Linear Technology

Specifications of LT6109IMS-1#TRPBF

• Lead Free Status / Rohs Status: Compliant

APPLICATIONS INFORMATION
When the EN/RST pin is transitioned from low to high to
enable the part, the amplifier output PMOS can turn on
momentarily causing current to flow into the SENSEHI
pin and out of the OUTA pin. Once the amplifier is entirely
turned on, the output will go to the correct current. Fig-
ure 16 shows this behavior and the impact it has on V
Circuitry connected to OUTA can be protected from these
transients by using an external diode to clamp V
capacitor to filter V
Power Up
After powering on the LT6109, the comparators must be
reset in order to guarantee a valid state at their outputs.
Fast supply ramps may cause a supply current transient
during start-up as shown in the Typical Performance
Characteristics. This current can be lowered by reducing
the edge speed of the supply.
EN/RST
OUTC1
OUTC2
V
2V/DIV
2V/DIV
EN/RST
V
OUTA
Figure 15. Comparator Reset Functionality
0V
0V
Figure 16. Amplifier Enable Response
t
RPW(MIN)
t
0.5µs
RESET
OUTA
2µs
.
RESET PULSE WIDTH LIMITS
t
RPW(MAX)
50µs/DIV
15µs
COMPARATORS
RESET
V
R
R
+
IN
OUT
= 60V
= 100
610912 F14
= 10k
610912 F13
OUTA
OUTA
or a
.
Reverse-Supply Protection
Some applications may encounter reverse-polarity sup-
plies. The LT6109 is not protected from a reversal of
supply polarity.
Error Budget
This current sense amplifier (Figure 17) operates by us-
ing an amplifier to replicate the sense voltage across an
external resistor, R
is conveyed through an output FET to an external resistor,
R
ratio of R
error sources contribute to the system accuracy of the
circuit shown in Figure 17. Note the second comparator
has been neglected to simplify analysis.
A summary of the worst-case errors over a 100°C tem-
perature range is shown in Table 2 and discussed below.
Note that the amplifier and comparator are very accurate
and the accuracy of most systems is limited by external
components.
Input Offset Voltage: The input offset voltage of the am-
plifier appears as an error in the voltage across R
resulting system error for a 100mV max V
Input Bias Current: The input bias current of the amplifier
subtracts from the current being fed from R
FET. The resulting error is:
I
across R
Gain Error: The gain error of the internal amplifier is a
measure of how accurately the sense voltage is forced
across R
resulting error is 0.2%
B
OUT
+
350nA •
100mV
450µV
is neglected since it produces very small voltage
, to produce an output voltage. The gain is set by the
SENSE
IN
OUT
. Since this is specified as a percentage the
= 0.45%
100mV
100Ω
/R
.
IN
. This section will describe how various
IN
LT6109-1/LT6109-2
= 0.035%
. The resulting current through R
IN
SENSE
to the output
is:
21
IN
. The
610912f
IN