Datasheet

15
LTC1642
1642fb
Uncommitted Comparator
The uncommitted comparator has an open drain output.
The comparator has 3mV of hysteresis: the output goes
high when the differential input voltage exceeds 1.5mV
and goes low when the differential input is less than
–1.5mV.
The comparator’s input transistors are MOSFETs so the
input bias and offset currents are very small: typically
picoamps at 25°C, increasing to nanoamps at 90°C. If the
auxiliary comparator is unused, the COMP
+
, COMP
–
and
COMPOUT pins may be left floating.
APPLICATIO S I FOR ATIO
WUU
U
R6
SENSE
RESISTOR, R2
TO SHORT
V
CC
PIN
R2
1642 F15
R5
V
CC
SENSE
ON GND
LT1642
I
LOAD
I
LOAD
Figure 15. Recommended Layout for R1, R2 and R5
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Layout Considerations
One ounce copper exhibits a sheet resistance of 530µΩ
per square. To minimize self-heating, traces should be
at least 0.02" wide per ampere of current and 0.03" is
recommended.
In high current applications, the voltage drop along traces
can be appreciable. Connect the LTC1642’s V
CC
and
SENSE pins
directly across sense resistor R2 to prevent
the power trace’s resistance from adding to R2. It is also
a good practice to keep the resistor divider to the ON pin
close to the chip and the divider’s connections to the V
CC
and GND pins short. Figure 15 shows an example layout.