LT6109IMS-1#TRPBF Linear Technology, LT6109IMS-1#TRPBF Datasheet - Page 14

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

Specifications of LT6109IMS-1#TRPBF

• Lead Free Status / Rohs Status: Compliant

LT6109-1/LT6109-2
APPLICATIONS INFORMATION
Output Voltage Error, ∆V
External Resistors
The LT6109 exhibits a very low gain error. As a result, the
gain error is determined primarily by the accuracy of the
external resistors used to set the gain. For instance, if
0.1% resistors are used for R
worst-case gain error is 0.4% with R
a graph of the maximum gain error which can be expected
versus the external resistor tolerance.
Output Current Limitations Due to Power Dissipation
The LT6109 can deliver a continuous current of 1mA to the
OUTA pin. This current flows through R
current sense amplifier via the SENSEHI pin. The power
dissipated in the LT6109 due to the output signal is:
14
V
P
Since V
BATT
OUT
R
I
SENSE
SENSE
R
R
IN
= (V
IN
+
Figure 6. Gain Error vs Resistor Tolerance
SENSEHI
10
0.1
10
1
Figure 5. R
1
0.01
SENSEHI
SENSEHI
SENSELO
LT6109
R
IN
≈ V
= 100
RESISTOR TOLERANCE (±%)
– V
IN
R
+
0.1
+
IN
, P
–
+
OUTA
Reduces Error Due to I
= 1k
OUT(GAIN ERROR)
OUTA
V
IN
+
) • I
9
V
V
5
+
–
and R
≈ (V
OUTA
1
+
IN
OUT
– V
= 100Ω. Figure 6 is
610912 F06
then the resulting
IN
OUTA
OUTA 8
610912 F05
, Due to
and enters the
10
B
) • I
OUTA
R
OUT
V
OUT
There is also power dissipated due to the quiescent power
supply current:
The comparator output current flows into the comparator
output pin and out of the V
the LT6109 due to each comparator is often insignificant
and can be calculated as follows:
The total power dissipated is the sum of these
dissipations:
At maximum supply and maximum output currents, the
total power dissipation can exceed 100mW. This will cause
significant heating of the LT6109 die. In order to prevent
damage to the LT6109, the maximum expected dissipa-
tion in each application should be calculated. This number
can be multiplied by the θ
maximum expected die temperature. Proper heat sinking
and thermal relief should be used to ensure that the die
temperature does not become excessive.
Output Filtering
The AC output voltage, V
makes filtering straightforward. Any circuit may be used
which generates the required Z
response. For example, a capacitor in parallel with R
will give a lowpass 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 R
SENSELO, SENSEHI Range
The difference between V
well as the maximum value of V
to ensure that the SENSELO pin doesn’t exceed the range
listed in the Electrical Characteristics table. The SENSELO
and SENSEHI pins of the LT6109 can function from 0.2V
P
P
P
f
S
OUTC1,C2
TOTAL
–3dB
= I
S
=
= P
• V
2 • π •R
= (V
+
OUTA
OUT
OUTC1,C2
+ P
1
OUT
will create an output pole at:
OUTC1
• C
OUT
L
BATT
– V
JA
–
, is simply I
pin. The power dissipated in
+ P
value, 160°C/W, to find the
–
OUT
SENSE
) • I
(see Figure 7) and V
OUTC2
OUTC1,C2
to get the desired filter
, must be considered
+ P
OUTA
S
• Z
OUT
. This
610912f
+
, as
OUT