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PDF AS1970 Data sheet ( Hoja de datos )
| Número de pieza | AS1970 | |
| Descripción | Low-Voltage Single/Dual/Quad Comparators | |
| Fabricantes | austriamicrosystems AG | |
| Logotipo |  |
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AS1970 - AS1975
Low-Voltage Single/Dual/Quad Comparators
Data Sheet
1 General Description
The AS1970 - AS1975 are single/dual/quad compara-
tors that operate with supplies from 2.5 to 5.5V making
them perfect for all 3- and 5-volt applications. The com-
parators can also operate with dual supplies (±1.25 to
±2.75V), and require very little supply current (down to
8.5µA) with minimal propagation delay (300ns).
Low input bias current (1.0pA, typ), low input offset volt-
age (0.5mV, typ), and internal hysteresis (3mV) make
these comparators ideal for low-power single-cell appli-
cations including power-management and power-moni-
toring systems.
The comparators are available as the standard products
listed in Table 1.
Table 1. Standard Products
Model
Output Type
AS1970/AS1972/AS1974
Push/Pull
AS1971/AS1973/AS1975
Open-Drain
The AS1970/AS1972/AS1974 push/pull output can sink
or source current.
The AS1971/AS1973/AS1975 open-drain output can be
pulled beyond VCC to a maximum of 5.5V > VEE. These
open-drain versions are ideal for logic-level translators
or bipolar-to-unipolar converters.
Large internal output drivers allow Rail-to-Rail output
swings with loads of up to 8mA.
The AS1970/AS1971 are available in a 5-pin SOT23
package. The AS1972/AS1973 are available in a 8-pin
MSOP package. The AS1974/AS1975 are available in a
14-pin TSSOP package.
Figure 1. Block Diagrams
2 Key Features
! CMOS Push/Pull Output Sinks and Sources 8mA
(AS1970/AS1972/AS1974)
! CMOS Open-Drain Output Voltage Extends Beyond
VCC (AS1971/AS1973/AS1975)
! Quiescent Supply Current: 8.5µA per Comparator
! Internal Hysteresis: 3mV
! 3V/5V Logic-Level Translation
! Single-Supply Operation: 2.5 to 5.5V
! Common-Mode Input Voltage Range Extends
250mV Above the Rails
! Low Propagation Delay: 300ns
! Minimized Overall Power Consumption
! Supply Current @1MHz Switching Frequency: 80µA
! No Phase Reversal for Overdriven Inputs
! Package Types:
- 5-pin SOT23 – AS1970/AS1971
- 8-pin MSOP – AS1972/AS1973
- 14-pin TSSOP – AS1974/AS1975
3 Applications
The devices are ideal for battery-powered systems,
mobile communication devices, zero-crossing detectors,
window comparators, level translators, threshold detec-
tors/discriminators, ground/supply-sensing applications,
IR receivers or any other space-limited application with
low power-consumption requirements.
IN+ +
IN- –
OUT
VCC
VEE
AS1970/AS1971
INA+
INA-
+
–
OUTA
INB+
INB-
+
–
OUTB
VCC AS1972/AS1973 VEE
INA+
INA-
INB+
INB-
INC+
INC-
IND+
IND-
VCC
+
–
+
–
+
–
+
–
AS1974/AS1975
OUTA
OUTB
OUTC
OUTD
VEE
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Revision 1.02
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1 page  
AS1970
Data Sheet - Electrical Characteristics
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Table 4. Electrical Characteristics (Continued)
Symbol
Parameter
Conditions
Min Typ Max Units
OUTx Rise Time
tRISE (AS1970/AS1972/AS1974 only)
VCC = 5V, CLOAD = 15pF
VCC = 5V, CLOAD = 50pF
32
50 ns
VCC = 5V, CLOAD = 200pF
80
VCC = 5V, CLOAD = 15pF
22
tFALL
OUTx Fall Time
VCC = 5V, CLOAD = 50pF
32 ns
VCC = 5V, CLOAD = 200pF
60
AS1970/AS1972/AS1974 only,
CLOAD = 15pF, 10mV Overdrive
400
AS1970/AS1972/AS1974 only,
CLOAD = 15pF, 100mV Overdrive
300
tPD- AS1971/AS1973/AS1975 only,
CLOAD = 15pF, RPULLUP = 5.1kΩ,
10mV Overdrive
Propagation Delay
AS1971/AS1973/AS1975 only, CLOAD =
15pF, RPULLUP = 5.1kΩ,
100mV Overdrive
400
300
ns
AS1970/AS1972/AS1974 only,
CLOAD = 15pF, 10mV Overdrive
420
tPD+
AS1970/AS1972/AS1974 only,
CLOAD = 15pF, 100mV Overdrive
270
tPU Power-Up Time
20 µs
1. Inferred from the VOS test. Both or either inputs can be driven 0.3V beyond either supply rail without output
phase reversal.
2. VOS is defined as the center of the hysteresis band at the input.
3. IB is defined as the average of the two input bias currents (IB-, IB+).
4. Guaranteed by design.
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5 Page 
AS1970
Data Sheet - Application Information
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4. Choose the trip point for VIN rising (VTHR) (see page 12). This is the threshold voltage at which the AS1970 -
AS1975 switches its output from low to high as VIN rises above the trip point. For this example, choose VTHR = 3V.
5. Calculate R2 as:
R2 = 1/[VTHR/(VREF x R1) - (1/R1) - (1/R3)]
Substituting the example values gives:
(EQ 5)
R2 = 1/[3.0V/(1.2V x 12kΩ) - (1/12kΩ) - (1/1.2MΩ)] = 8.05kΩ
In this example, a standard 8.2kΩ resistor should be used for R2.
6. Verify the trip voltages and hysteresis as:
VTHR = VREF x R1[(1/R1) + (1/R2) + (1/R3)]
VTHF = VTHR - (R1 x VCC/R3)
Hysteresis = VTHR - VTHF
(EQ 6)
(EQ 7)
(EQ 8)
Hysteresis (AS1971/AS1973/AS1975)
The AS1971/AS1973/AS1975 have 3mV internal hysteresis. Their open-drain outputs require an external pullup resis-
tor (Figure 19), and additional hysteresis can be generated using positive feedback.
Figure 19. Additional Hysteresis AS1971/AS1973/AS1975
R1
VIN
R2
VCC
R3
+ VCC
VEE
–
VREF
OUT
R4
Resistor Selection Example
For the circuit shown in Figure 19, the following steps can be used to calculate values for R1, R2, R3, and R4:
1. Select R3 according to one of:
R3 = VREF/500µA
R3 = (VREF - VCC)/500µA - R4
Use the smaller of the two resulting resistor values.
(EQ 9)
(EQ 10)
2. Choose the hysteresis band required (VHB). For this example, use 50mV.
3. Calculate R1 as:
R1 = (R3 + R4)(VHB/VCC)
(EQ 11)
4. Choose the trip point for VIN rising (VTHR) (see page 12). This is the threshold voltage at which the comparator
switches its output from low to high as VIN rises above the trip point.
5. Calculate R2 as:
R2 = 1/[VTHR /(VREF x R1) - (1/R1) - 1/(R3 + R4)]
6. Verify the trip voltages and hysteresis as follows:
(EQ 12)
VIN rising: VTHR = VREF x R1 x [1/R1 + 1/R2 + 1/(R3 + R4)]
VIN falling: VTHF = VREF x R1 x [1/R1 + 1/R2 + 1/(R3+R4)] - 1/(R3+R4) x VCC
Hysteresis = VTHR - VTHF
(EQ 13)
(EQ 14)
(EQ 15)
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| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet AS1970.PDF ] | |
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| Número de pieza | Descripción | Fabricantes |
| AS1970 | Low-Voltage Single/Dual/Quad Comparators | austriamicrosystems AG |
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| AS1972 | Low-Voltage Single/Dual/Quad Comparators | austriamicrosystems AG |
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