AS1976-T austriamicrosystems, AS1976-T Datasheet - Page 12

• Manufacturer Part Number: AS1976-T
• Description: IC COMPARATOR PUSH/PULL SOT23-5
• Manufacturer: austriamicrosystems

Specifications of AS1976-T

• Comparator Type: General Purpose
• No. Of Comparators: 1
• Response Time: 15µs
• Ic Output Type: Push Pull
• Supply Current: 200nA
• Supply Voltage Range: 1.8V To 5.5V
• Amplifier Case Style: SOT-23
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AS1976/AS1977
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
Additional Hysteresis (AS1976)
Additional hysteresis can be added to the AS1976 and AS1978 with three resistors and positive feedback
27), however, this positive feedback method slows hysteresis response time.
Figure 27. AS1976 Additional Hysteresis
Resistor Selection Example
For the circuit shown in
1. First select the value for R
2. Choose the required hysteresis band (V
3. Calculate R
4. Choose the trip point for V
5. Calculate R
6. Verify the trip voltages and hysteresis as:
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0.2µA to minimize errors due to leakage current. The current through R
Taking into consideration the two possible output states, solving for R
Use the smaller of the two resulting values for R
two resistor values are 1.2M Ω and 2.0M Ω , therefore choose a 1.2M Ω standard resistor for R
Substituting the R
Substituting the R
In this example, a standard 8.2k Ω resistor should be used for R
1
2
as:
as:
1
1
and V
and R
Figure
HB
3
R
3
IN
example values gives:
. Leakage current at IN is less than 2nA, thus the current through R
2
27, use the following steps to calculate values for R
example values gives:
rising (V
= 1/[3.0V/(1.2V x 12k Ω ) - (1/12k Ω ) - (1/1.2M Ω )] = 8.05k Ω
V
IN
V
R
THR
2
= 1/[V
THR
= V
V
R
THF
Hysteresis = V
HB
1
) such that V
REF
THR
R
R
). For this example, choose 33mV.
R
1
3
R
2
= V
(V
= 1.2M Ω (50mV/3.3V) = 12k Ω
/(V
x R
= (V
1
R
REF
= R
3
THR
REF
3
1
= V
. For example, for V
[(1/R
CC
Revision 1.01
- V
3
(V
x R
- (R
REF
- V
V
OUT
THR
HB
REF
1
THR
1
) + (1/R
1
R
REF
/I
) - (1/R
/V
3
x V
)/R
R3
> V
CC
- V
)/I
+
–
3
CC
)
R3
REF
V
V
THF
V
CC
EE
2
/R
1
CC
2
) + (1/R
) - (1/R
.
(R
3
)
1
+ R
REF
3
yields two formulas:
3
3
3
)]
3
)]
at the trip point is:
= 1.245V, V
)/R
3
OUT
. For this example, choose 3V.
1
, R
2
, and R
CC
= 3.3V, and I
3
3
.
.
3
should be at least
R3
(see Figure
= 1µA, the
12 - 17
(EQ 1)
(EQ 2)
(EQ 3)
(EQ 4)
(EQ 5)
(EQ 6)
(EQ 7)
(EQ 8)