LTC6101HV Linear Technology, LTC6101HV Datasheet - Page 12

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

LTC6101/LTC6101HV
12
APPLICATIO S I FOR ATIO
If the offset current, I
the 100 microvolt error above is reduced to 2 microvolts.
Adding R
of the circuit. For less sensitive designs, R
necessary.
Example:
If an I
3V/1A
Then, from the Electrical Characteristics of the LTC6101,
R
500mΩ
Gain = R
= 6
If the maximum output current, I
R
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
the 70dB performance of the LTC6101 makes this applica-
tion feasible.
Output Error, E
Gain, A
This errors 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 flows through R
the 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 supply
current:
SENSE
OUT
P
Since V
OUT
equals 3V/1mA ≈ 3.01 kΩ (1% value) and R
SENSE
OL
≈ V
OUT
= (V
IN
, of the LTC6101 Amplifier
–IN
+
/R
SENSE
as described will maximize the dynamic range
–IN
range = (1A to 1mA) and (V
≈ V
IN
OUT
– V
= V
+
, P
(max) / I
, Due to the Finite DC Open Loop
OUT
U
OUT
IN
OS
OUT
+
) • I
(max) / V
, of the LTC6101 amplifier is 2nA,
= R
≈ (V
U
OUT
IN
SENSE
–
+
.
– V
OS
SENSE
OUT
is 3k x 2nA = ±6µVolts
(max) = 500mV/1A =
OUT
W
SENSE
, is limited to 1mA,
(max) = 3V/500mV
) • I
OL
of the LTC6101
OUT
= 1mA to 1A),
OUT
IN
and enters
U
IN
/I
IN
SENSE
+
= 3kΩ/
is not
) =
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 significant 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 find 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
Typical Performance Characteristics section.) In this con-
dition, the maximum output current should be reduced to
avoid device damage. Note that the MSOP package has a
larger θ
when operating the LTC6101A/LTC6101HVA at high tem-
peratures 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
P
P
P
P
T
T
T
P
will be 104°C
RISE
MAX
MAX
Q
TOTAL
Q(MAX)
OUT(MAX)
TOTAL(MAX)
= I
JA
= θ
= T
must be < 150°C
DD
= P
than the S5, so additional care must be taken
= I
• V
AMBIENT
JA
OUT
= I
DD(MAX)
• P
+
Q
≈ 96mW and the max die temp
OUT
, is proportional to temperature. Refer to
TOTAL(MAX)
+ P
+ T
• V
Q
• V
+
RISE
(MAX)
+
(MAX)
= 60mW
= 41.4mW
JA
value listed in the
6101fa