LTC6102HV Linear Technology, LTC6102HV Datasheet - Page 12

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

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APPLICATIONS INFORMATION
LTC6102/LTC6102HV
As temperature increases, the leakage of the ESD protec-
tion diodes on the inputs increases the input bias currents
of both inputs in the positive direction, while the current
caused by the charge injection stays relatively constant. At
temperatures above 70°C, the leakage current dominates
and both the negative and positive pins’ input bias currents
are in the positive direction (into the pins).
Output Current Limitations Due to Power Dissipation
The LTC6102 can deliver more than 1mA continuous cur-
rent to the output pin. This current fl ows through R
enters the current sense amp via the –INF pin. The power
dissipated in the LTC6102 due to the output current is:
There is also power dissipated due to the quiescent sup-
ply current:
The total power dissipated is the output current 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 LTC6102 die. In order to
prevent damage to the LTC6102, 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 LTC6102 in the MSOP package is
to be biased at 55V ±5V supply with 1mA output current
at 80°C:
12
P
Since V
P
P
P
P
OUT
Q
TOTAL
Q(MAX)
OUT(MAX)
= I
= (V
S
= P
–INF
• V
= I
–INF
+
OUT
= I
DD(MAX)
≈ V
OUT
– V
+ P
+
, P
OUT
• V
Q
OUT
• V
+
) • I
(MAX)
+
≈ (V
(MAX)
OUT
= 60mW
+
– V
= 39mW
OUT
JA
value listed in the
) • I
OUT
IN
and
If this same circuit must run at 125°C, the max die temp
will increase to 155°C. (Note that supply current, and
therefore P
Performance Characteristics section.) In this condition,
the maximum output current should be reduced to avoid
device damage. Note that the DD package has a smaller θ
than the MSOP package, which will substantially reduce
the die temperature at similar power levels.
The LTC6102HV 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 LTC6102 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 and input resistors and, if input fault
conditions are likely, an external clamp.
Output Filtering
The output voltage, V
makes fi ltering straightforward. Any circuit may be used
which generates the required Z
response. For example, a capacitor in parallel with R
will give a low pass response. This will reduce unwanted
noise from the output, and may also be useful as a charge
reservoir to keep the output steady while driving a switch-
ing circuit such as a mux or ADC. This output capacitor
in parallel with an output resistor will create a pole in the
output response at:
T
T
T
P
will be 110°C
f
RISE
MAX
MAX
TOTAL(MAX)
–
3
dB
= T
must be < 125°C
= θ
=
Q
AMBIENT
2
JA
, is proportional to temperature. Refer to Typical
• •
• P
π
≈ 99mW and the max die temp
TOTAL(MAX)
R
OUT
+ T
1
OUT
RISE
•
C
, is simply I
OUT
OUT
to get the desired fi lter
OUT
• Z
OUT
. This
OUT
6102f
JA