TC1040CEUATR Microchip Technology, TC1040CEUATR Datasheet - Page 5

• Manufacturer Part Number: TC1040CEUATR
• Description: IC DUAL COMPARATOR W/VREF 8MSOP
• Manufacturer: Microchip Technology
• Type: with Voltage Referencer

Specifications of TC1040CEUATR

• Output Type: Rail-to-Rail
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• Number Of Elements: 2
• Voltage - Supply: 1.8 V ~ 5.5 V
• Mounting Type: Surface Mount
• Number Of Channels: 2 Channels
• Product: Analog Comparators
• Response Time: 6 us
• Offset Voltage (max): 5 mV
• Input Bias Current (max): 0.0001 uA
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 1.8 V
• Supply Current (max): 0.01 mA
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Request inventory verification / Request inventory verification

4.2
Figure 4-2 is a precision battery low/battery dead
monitoring circuit. Typically, the battery low output
warns the user that a battery dead condition is
imminent. Battery dead typically initiates a forced
shutdown to prevent operation at low internal supply
voltages (which can cause unstable system operation).
The circuit in Figure 4-2 uses a single TC1040, one-
half of a TC1029, and only six external resistors.
COMPA and COMPB provide precision voltage
detection using V
R4 set the detection threshold for BATT LOW, while
Resistors R1 and R7 set the detection threshold for
BATT FAIL. The component values shown assert
BATT LOW at 2.2V (typical) and BATT FAIL at 2.0
(typical). Total current consumed by this circuit is
typically 22μA at 3V. Resistors R5 and R6 provide
hysteresis for comparators COMPA and COMPB,
respectively.
4.3
Hysteresis can be set externally with two resistors
using positive feedback techniques (see Figure 4-3).
The design procedure for setting external comparator
hysteresis is as follows:
1.
2.
© 2005 Microchip Technology Inc.
Choose the feedback resistor R
input bias current of the comparator is at most
100pA, the current through R
100nA (i.e., 1000 times the input bias current)
and retain excellent accuracy. The current
through R
R
Determine the hysteresis voltage (V
the upper and lower thresholds.
C
where V
Precision Battery Monitor
External Hysteresis (Comparator)
C
at the comparator’s trip point is V
R
R
is a stable reference voltage.
as a reference. Resistors R2 and
C
can be set to
C
HY
. Since the
) between
R
/
3.
EQUATION 4-1:
4.
5.
EQUATION 4-2:
6.
EQUATION 4-3:
EQUATION 4-4:
V
Calculate R
Choose the rising threshold voltage for V
(V
Calculate R
Verify the threshold voltages with these
formulas:
V
SRC
SRC
V
THR
THR
rising:
).
falling:
R
V
=
B
THF
=
(
A
B
V
as follows:
as follows:
R
---------------------------------------------------------- -
=
R
⎛
⎝
) R
-------------------- -
V
(
A
V
V
R
THR
=
A
THR
×
)
R
R
⎛
⎝
–
C
A
------ -
R
1
⎛
⎝
1
⎞
⎠
A
⎛
⎝
---------- -
V
V
–
⎞
⎠
R
------------------------ -
------ -
R
HY
DD
+
1
A
A
⎛
⎝
⎞
⎠
R
×
TC1040
–
------ -
R
C
1
V
-------
R
B
1
DD
DS21345C-page 5
⎞
⎠
C
+
⎞
⎠
⎛
⎝
-------
R
1
C
⎞
⎠
SRC