LTC6101HV Linear Technology, LTC6101HV Datasheet - Page 12

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

LTC6101/LTC6101HV
APPLICATIONS INFORMATION
12
If the offset current, I
the 100 microvolt error above is reduced to 2 microvolts.
Adding R
range of the circuit. For less sensitive designs, R
not necessary.
Example:
If an I
3V/1A
Then, from the Electrical Characteristics of the LTC6101,
R
500mΩ
Gain = R
3V/500mV = 6
If the maximum output current, I
R
3kΩ/6 ≈ 499Ω (1% value).
The output error due to DC offset is ±900μVolts (typ) and
the error due to offset current, I
(typical), provided R
The maximum output error can therefore reach ±906μVolts
or 0.03% (–70dB) of the output full scale. Considering
the system input 60dB dynamic range (I
1A), the 70dB performance of the LTC6101 makes this
application feasible.
Output Error, E
Gain, A
This error is inconsequential as the A
is very large.
Output Current Limitations Due to Power Dissipation
The LTC6101 can deliver up to 1mA continuous current to
the output pin. This current fl ows through R
current sense amp via the IN(–) pin. The power dissipated
in the LTC6101 due to the output signal is:
There is also power dissipated due to the quiescent sup-
ply current:
SENSE
OUT
P
Since V
P
OUT
Q
equals 3V/1mA ≈ 3.01 kΩ (1% value) and R
= I
SENSE
OL
≈ V
= (V
DD
IN
, of the LTC6101 Amplifi er
–IN
OUT
+
SENSE
• V
–IN
range = (1A to 1mA) and (V
≈ V
as described will maximize the dynamic
/R
+
OUT
– V
IN
+
, Due to the Finite DC Open Loop
, P
(max) / I
OUT
= V
IN
OUT
OS
+
) • I
, of the LTC6101 amplifi er is 2nA,
= R
OUT
≈ (V
OUT
IN
SENSE
(max) / V
–
+
.
– V
OS
OUT
is 3k x 2nA = ±6μVolts
OUT
(max) = 500mV/1A =
, is limited to 1mA,
) • I
OL
SENSE
SENSE
of the LTC6101
IN
OUT
OUT
and enters the
/I
= 1mA to
(max) =
SENSE
IN
IN
+
) =
is
=
The total power dissipated is the output dissipation plus
the quiescent dissipation:
At maximum supply and maximum output current, the
total power dissipation can exceed 100mW. This will
cause signifi cant heating of the LTC6101 die. In order to
prevent damage to the LTC6101, the maximum expected
dissipation in each application should be calculated. This
number can be multiplied by the θ
package section on page 2 to fi nd the maximum expected
die temperature. This must not be allowed to exceed 150°C,
or performance may be degraded.
As an example, if an LTC6101 in the S5 package is to be
run at 55V ±5V supply with 1mA output current at 80°C:
If this same circuit must run at 125°C, the max die
temp will increase to 150°C. (Note that supply current,
and therefore P
to Typical Performance Characteristics section.) In this
condition, the maximum output current should be reduced
to avoid device damage. Note that the MSOP package
has a larger θ
taken when operating the LTC6101A/LTC6101HVA at high
temperatures and high output currents.
The LTC6101HV can be used at voltages up to 105V. This
additional voltage requires that more power be dissipated
for a given level of current. This will further limit the allowed
output current at high ambient temperatures.
It is important to note that the LTC6101 has been designed
to provide at least 1mA to the output when required, and
can deliver more depending on the conditions. Care must
be taken to limit the maximum output current by proper
choice of sense resistor and, if input fault conditions exist,
external clamps.
P
P
P
T
T
T
P
will be 104°C
TOTAL
RISE
MAX
MAX
TOTAL(MAX)
Q(MAX)
OUT(MAX)
= T
must be < 150°C
= θ
= P
= I
AMBIENT
JA
OUT
= I
DD(MAX)
JA
• P
≈ 96mW and the max die temp
Q
OUT
than the S5, so additional care must be
, is proportional to temperature. Refer
TOTAL(MAX)
+ P
+ T
• V
Q
• V
RISE
+
(MAX)
+
(MAX)
= 60mW
= 41.4mW
JA
value listed in the
6101fg