LTC6102HV Linear Technology, LTC6102HV Datasheet - Page 15

• Manufacturer Part Number: LTC6102HV
• Description: Zero Drift High Side Current Sense Amplifier
• Manufacturer: Linear Technology

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APPLICATIONS INFORMATION
in order to close the internal loop. This results in current
fl owing through R
rate will be determined by the amplifi er and FET charac-
teristics as well as the input resistor, R
R
decreasing the response time at the output. This will also
have the effect of increasing the maximum output current.
Using a larger R
since V
R
gain of the circuit.
Bandwidth
For applications that require higher bandwidth from the
LTC6102, care must be taken in choosing R
eral-purpose op-amp, the gain-bandwidth product is used
to determine the speed at a given gain. Gain is determined
by external resistors, and the gain-bandwidth product is
an intrinsic property of the amplifi er. The same is true
for the LTC6102, except that the feedback resistance is
determined by an internal FET characteristic. The feedback
impedance is approximately 1/g
The impedance is reduced as current into –INF is increased.
At 1mA, the impedance of the MOSFET is on the order of
10kΩ. R
as 1/(R
(R
IN
OUT
IN
will allow the output current to increase more quickly,
• g
will both have the effect of increasing the voltage
IN
OUT
m
IN
), with a maximum bandwidth of around 2MHz.
• g
sets the closed-loop gain of the internal loop
= I
m
). The bandwidth is then limited to GBW •
OUT
OUT
IN
• R
and the internal FET. This current slew
will also decrease the response time,
OUT
. Reducing R
m
of the internal MOSFET.
IN
IN
. Using a smaller
and increasing
IN
. For a gen-
This is illustrated in the characteristic curves, where gain
vs frequency for two input conditions is shown. The exact
impedance of the MOSFET is diffi cult to determine, as it
is a function of input current, process, and capacitance,
and has a very different characteristic for low currents
vs high currents. However, it is clear that smaller values
of R
lower closed-loop bandwidth. V
chosen to maximize both I
highest speed. Theoretically, maximum bandwidth would
be achieved for the case where V
giving I
this may not be possible in a practical application. Note
that the MOSFET g
value of I
small AC input will help increase the bandwidth.
V
The LTC6102 has an internally regulated supply near V+
for internal bias. It is not intended for use as a supply or
bias pin for external circuitry. A 0.1μF capacitor should be
connected between the V
should be located very near to the LTC6102 for the best
performance. In applications which have large supply tran-
sients, a 6.8V zener diode may be used in parallel with this
bypass capacitor for additional transient suppression.
REG
IN
Bypassing
and smaller values of I
OUT
OUT
= 1mA and a closed-loop gain near 1. However,
, not the peak value. Adding DC current to a
LTC6102/LTC6102HV
m
is determined by the average or DC
REG
OUT
and V
OUT
and closed-loop gain for
IN
SENSE
= 10VDC and R
will generally result in
+
pins. This capacitor
and R
IN
should be
IN
15
= 10k,
6102f