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SEMICONDUCTOR
ICL8211, ICL8212
Programmable Voltage Detectors
Description
The Harris ICL8211/8212 are micropower bipolar monolithic integrated circuits intended primarily for precise voltage detection and generation. These circuits consist of an accurate voltage reference, a comparator and a pair of output buffer/drivers. Specifically, the ICL8211 provides a 7mA current limited output sink when the voltage applied to the `THRESHOLD' terminal is less than 1.15V (the internal reference). The ICL8212 requires a voltage in excess of 1.15V to switch its output on (no current limit). Both devices have a low current output (HYSTERESIS) which is switched on for input voltages in excess of 1.15V. The HYSTERESIS output may be used to provide positive and noise free output switching using a simple feedback network.
April 1994
Features
* High Accuracy Voltage Sensing and Generation * Internal Reference 1.15V Typical * Low Sensitivity to Supply Voltage and Temperature Variations * Wide Supply Voltage Range Typ. 1.8V to 30V * Essentially Constant Supply Current Over Full Supply Voltage Range * Easy to Set Hysteresis Voltage Range * Defined Output Current Limit ICL8211 * High Output Current Capability ICL8212
Applications
* Low Voltage Sensor/Indicator * High Voltage Sensor/Indicator * Nonvolatile Out-of-Voltage Range Sensor/Indicator * Programmable Voltage Reference or Zener Diode * Series or Shunt Power Supply Regulator * Fixed Value Constant Current Source
Ordering Information
PART NUMBER ICL8211CPA ICL8211CBA ICL8211CTY ICL8211MTY (Note 1) ICL8212CPA ICL8212CBA ICL8212CTY ICL8212MTY (Note 1) NOTE: 1. Add /883B to part number if 883B processing is required TEMPERATURE RANGE 0oC to +70oC 0oC to +70oC 0oC to +70oC -55oC to +125oC PACKAGE 8 Lead Plastic DIP 8 Lead SOlC (N) 8 Pin Metal Can 8 Pin Metal Can 8 Lead Plastic DIP 8 Lead SOlC (N) 8 Pin Metal Can 8 Pin Metal Can
0oC to +70oC 0oC to +70oC 0oC to +70oC -55oC to +125oC
Pinouts
ICL8211 (PDIP, SOIC) TOP VIEW ICL8211 (CAN) TOP VIEW
HYSTERESIS NC HYSTERESIS THRESHOLD OUTPUT 1 2 3 4 8 7 6 5 V+ NC NC OUTPUT GROUND NC 3 4 GROUND 5 NC 2 6 NC THRESHOLD 1 8 7 V+
CAUTION: These devices are sensitive to electrostatic discharge. Users should follow proper I.C. Handling Procedures. Copyright
(c) Harris Corporation 1992
File Number
3184.1
7-161
ICL8211, ICL8212 Functional Diagram
VOLTAGE REFERENCE COMPARATOR OUTPUT BUFFERS 8 V+ Q3 Q2 Q4 Q16 Q17 Q18 R5 4.5k
2 R4 1M Q5 Q1 Q6 Q14 Q15 XXXX Q19 HYST
1.15V
VREF Q12 Q13
3 THRESHOLD
Q7 R1 20M
Q23
R3 360k
4 OUTPUT Q8 Q9 Q10 Q11 Q20 R6 100k
Q21
R2 30k 5 GROUND ICL8211 OPTION XXXXXX ICL8212 OPTION
7-162
Specifications ICL8211, ICL8212
Absolute Maximum Ratings
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to +30V Output Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to +30V Hysteresis Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . +0.5V to -10V Threshold Input Voltage . . . . . . . . . . . . . +30V to -5V with respect to GROUND and +0V to -30V with respect to V+ Current into Any Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30mA
Thermal Information
Thermal Resistance JA JC Plastic DIP Package . . . . . . . . . . . . . . . . 150oC/W Plastic SOIC Package . . . . . . . . . . . . . . . 180oC/W Metal Can . . . . . . . . . . . . . . . . . . . . . . . . 156oC/W 68oC/W Lead Temperature (Soldering, 10s). . . . . . . . . . . . . . . . . . . . . 300oC (SOIC - Lead Tips Only) Current into Any Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30mA
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
Operating Conditions
Operating Temperature Range ICL8211M/8212M . . . . . . . . . . . . . . . . . . . . . . . . -55oC to +125oC ICL8211C/8212C . . . . . . . . . . . . . . . . . . . . . . . . . . . 0oC to +70oC Storage Temperature Range. . . . . . . . . . . . . . . . . . -65oC to +150oC
Electrical Specifications
PARAMETER Supply Current
V+ = 5V, TA = +25oC Unless Otherwise Specified ICL8211 ICL8212 MAX 40 250 1.19 1.19 1.20 MIN 50 10 1.00 1.00 1.05 TYP 110 20 1.15 1.145 1.165 -0.5 MAX 250 40 1.19 1.19 1.20 UNITS A A V V V mV
SYMBOL I+
TEST CONDITIONS 2.0 < V+ < 30 VTH = 1.3V VTH = 0.9V
MIN 10 50 0.98 0.98 1.00 -
TYP 22 140 1.15 1.145 1.165 -0.8
Threshold Trip Voltage
VTH
IOUT = 4mA VOUT = 2V
V+ = 5V V+ = 2V V+ = 30V
Threshold Voltage Disparity Between Output & Hysteresis Output Guaranteed Operating Supply Voltage Range Minimum Operating Supply Voltage Range
VTHP
IOUT = 4mA IHYST = 7mA VOUT = 2V VHYST = 3V +25oC (Note 3) 0oC to +70oC (Note 3)
VSUPPLY
2.0 2.2 -
1.8 1.4 1.5 200 1.0
30 30 -
2.0 2.2 -
1.8 1.4 2.5 200 1.0
30 30 -
V V V V V ppm/oC mV
VSUPPLY
+25oC +125oC -55oC
Threshold Voltage Temperature Coefficient Variation of Threshold Voltage with Supply Voltage Threshold Input Current
VTH/T VTH/V+
IOUT = 4mA, VOUT = 2V V+ = 10% at V+ = 5V
ITH
VTH = 1.15V VTH = 1.00V
VTH = 0.9V VTH = 1.3V 4 -
100 5 0.17 7.0 -
250 10 1 0.4 12 0.1
15 -
100 5 0.17 35 -
250 10 1 0.4 0.1
nA nA A A A A V V mA mA A
Output Leakage Current
IOLK
VOUT = 30V
VOUT = 5V
VTH = 0.9V VTH = 1.3V
Output Saturation Voltage Max Available Output Current Hysteresis Leakage Current
VSAT
IOUT = 4mA
VTH = 0.9V VTH = 1.3V
IOH
(Notes 3 & 4) VOUT = 5V V+ = 10V, VHYST = GND
VTH = 0.9V VTH = 1.3V VTH = 1.0V
ILHYS
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ICL8211, ICL8212
Electrical Specifications
PARAMETER Hysteresis Sat Voltage V+ = 5V, TA = +25oC Unless Otherwise Specified (Continued) ICL8211 SYMBOL VHYS(MAX) TEST CONDITIONS IHYST = -7A, measured with respect to V+ VTH = 1.3V MIN TYP -0.1 MAX -0.2 MIN ICL8212 TYP -0.1 MAX -0.2 UNITS V
Max Available Hysteresis Current
IHYS (MAX)
VTH = 1.3V
-15
-21
-
-15
-21
-
A
Electrical Specifications
ICL8211MTY/8212MTY
V+ = 5V, TA = -55oC to +125oC ICL8211 ICL8212 MAX 100 350 1.30 1.30 30 400 20 0.5 15 0.2 0.3 MIN 0.80 0.80 2.8 9 TYP 350 100 MAX 350 100 1.30 1.30 30 400 20 0.5 0.2 0.3 UNITS A A V V V nA A A V V mA mA A V
PARAMETER Supply Current
SYMBOL I+
TEST CONDITIONS 2.8 < V+ < 30 VT = 1.3V VT = 0.8V
MIN -
TYP -
Threshold Trip Voltage
VTH
IOUT = 2mA VOUT = 2V (Note 5) VTH = 1.15V VOUT = 30V
V+ = 2.8V V+ = 30V
0.80 0.80 2.8 -
Guaranteed Operating Supply Voltage Range Threshold Input Current Output Leakage Current
VSUPPLY ITH IOLK
VTH = 0.8V VTH = 1.3V
3 -
Output Saturation Voltage Max Available Output Current Hysteresis Leakage Current Hysteresis Saturation Voltage Max Available Hysteresis Current NOTES:
VSAT
IOUT = 3mA
VTH = 0.8V VTH = 1.3V
IOH
(Notes 3 & 4) VOUT = 5V V+ = 10V VHYST = GND IHYST = -7A measured with respect to V+
VTH = 0.8 VTH = 1.3V VTH = 0.8V VTH = 1.3V
ILHYS VHYS(MAX)
IHYS (MAX)
VTH = 1.3V
10
-
-
10
-
-
A
1. The maximum output current of the ICL8211 is limited by design to 15mA under any operating conditions. The output voltage may be sustained at any voltage up to +30V as long as the maximum power dissipation of the device is not exceeded. 2. The maximum output current of the ICL8212 is not defined. And systems using the ICL8212 must therefore ensure that the output current does not exceed 30mA and that the maximum power dissipation of the device is not exceeded. 3. Threshold Trip Voltage is 0.80V(min) to 1.30V(mas). At IOUT = 3mA.
7-164
ICL8211, ICL8212 Typical Performance Curves
10,000 HYSTERESIS OUTPUT CURRENT (A) THRESHOLD INPUT CURRENT (nA) TA = +25oC V+ = +10V
(ICL8211 and ICL8212)
0 V+ = +5V VTH = 1.2V -5 VHYS = 4.5V (OR -0.5V WITH RESPECT TO V+ SUPPLY) -10
1,000 ICL8211 OR ICL8212
-20
100
-25 ICL8211 OR ICL8212 -30
10 0.0 1.1 1.15 1.2 2.0 3.0 6.0 8.0 10.0 -40 -20 0 +20 +40
o
+60
+80
THRESHOLD VOLTAGE (VTH) (IRREGULAR SCALE)
TEMPERATURE ( C)
FIGURE 1. THRESHOLD INPUT CURRENT AS A FUNCTION OF THRESHOLD VOLTAGE
FIGURE 2. HYSTERESIS OUTPUT SATURATION CURRENT AS A FUNCTION OF TEMPERATURE
Typical Performance Curves
150
(ICL8211 ONLY)
150 VTH = 0.9V SUPPLY CURRENT (A) 125 100 75 50 25 TA = +25oC V+ = +5V OUTPUTS OPEN CIRCUIT
125 SUPPLY CURRENT (A) 100
TA = +25oC OUTPUTS OPEN CIRCUIT
75
50
25 VTH = 1.3V 0 10 20 30 0 0.0 SUPPLY VOLTAGE 1.0 1.1 1.15 1.2 2.0 THRESHOLD VOLTAGE (VTH) (IRREGULAR SCALE) 4.0
FIGURE 3. SUPPLY CURRENT AS A FUNCTION OF SUPPLY VOLTAGE
150 125 SUPPLY CURRENT (A) 100 75 50 25 0 -55 -25 +5 +35 +65 +95 +125 TEMPERATURE oC VTH = 0.9V
FIGURE 4. SUPPLY CURRENT AS A FUNCTION OF THRESHOLD VOLTAGE
12 0 TA = +25oC V+ = +5V -5 VO = 0.5V VHYS = V+ - 0.25V -10 HYSTERESIS OUTPUT OUTPUT -15 -20 -25 8mV 0 1.12 1.13 1.14 1.15 1.16 1.17 THRESHOLD VOLTAGE -30 1.18
HYSTERESIS OUTPUT CURRENT (A)
10 OUTPUT CURRENT (mA) 8 6
VTH = 1.3V
4 2
FIGURE 5. SUPPLY CURRENT AS A FUNCTION OF TEMPERATURE
FIGURE 6. OUTPUT SATURATION CURRENTS AS A FUNCTION OF THRESHOLD VOLTAGE
7-165
ICL8211, ICL8212 Typical Performance Curves
OUTPUT 1.15 THRESHOLD VOLTAGE THRESHOLD VOLTAGE 1.17
(ICL8211 ONLY)
(Continued)
1.18 IO = 4mA, VO = 1V IHYS = -7A, VHYS = (V+ -2) V
1.16 OUTPUT 1.15 HYSTERESIS OUTPUT 1.14
1.14 HYSTERESIS OUTPUT
1.13
V+ = +5V IO = 1mA, VOUT = +5V IHYS = -7A, VHST = 0V -25 +5 +35 +65 TEMPERATURE (oC) +95 +125
-55
1.13 1 2 3 45 10 20 30 4050 SUPPLY VOLTAGE 100
FIGURE 7. THRESHOLD VOLTAGE TO TURN OUTPUTS "JUST ON" AS A FUNCTION OF TEMPERATURE
FIGURE 8. THRESHOLD VOLTAGE TO TURN OUTPUTS "JUST ON" AS A FUNCTION OF SUPPLY VOLTAGE
8
12
TA = +25oC V+ = +5V
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
9
7
VTH = 1.0V 6
6 V+ = +5V VTH = 1.1V VO = 1.0V 5 -55 -25 +5 +35 +65 +95 +125
VTH = 1.147V 3
0 0.1 TEMPERATURE (oC)
VTH = 1.152V 1.0 10.0 OUTPUT VOLTAGE 100.0
FIGURE 9. OUTPUT SATURATION CURRENT AS A FUNCTION OF TEMPERATURE
FIGURE 10. OUTPUT CURRENT AS A FUNCTION OF OUTPUT VOLTAGE
0 HYSTERESIS OUTPUT CURRENT (A) -5 -10 -15 -20 -25 -30 -35 -40 -10.00 VT = 1.18V TA = +25oC V+ = +10V VT = 1.144V VT = 1.143V
-1.00
-0.10
-0.01
HYSTERESIS OUTPUT VOLTAGE
FIGURE 11. HYSTERESIS OUTPUT CURRENT AS A FUNCTION OF HYSTERESIS OUTPUT VOLTAGE
7-166
ICL8211, ICL8212 Typical Performance Curves
150 TA = +25oC OUTPUTS OPEN CIRCUIT SUPPLY CURRENT - I+ (A)
(ICL8212 ONLY)
150 TA = +25oC V+ = +5V OUTPUTS OPEN CIRCUIT
125 SUPPLY CURRENT (A)
125
100
VTH = 1.3V
100
75
75
50
50
25 25 VTH = 0.9V 0 0 10 20 30 SUPPLY VOLTAGE 0 0.0 1.0 1.1 1.15 1.2 2.0 4.0 THRESHOLD VOLTAGE (VTH) (IRREGULAR SCALE)
FIGURE 12. SUPPLY CURRENT AS A FUNCTION OF SUPPLY VOLTAGE
FIGURE 13. SUPPLY CURRENT AS A FUNCTION OF THRESHOLD VOLTAGE
150 125 100 75 50 25 0 -55 -25 +5 +35 +65 +95 +125 TEMPERATURE (oC) V+ = 5V OUTPUTS OPEN CIRCUIT VTH = 1.3V OUTPUT CURRENT (mA)
30 25 20 15 10 5 OUTPUT 0 1.14 1.15 1.16 1.17 1.18 1.19 TA = V+ = 5V VOUT = 4V VHYS = V+ -0.25V HYSTERESIS OUTPUT +25oC
0 -5 -10 -15 -20 -25 -30 1.20 HYSTERESIS OUTPUT CURRENT (A) 100
SUPPLY CURRENT - I+ (A)
VTH = 0.9V
THRESHOLD VOLTAGE
FIGURE 14. SUPPLY CURRENT AS A FUNCTION OF TEMPERATURE
FIGURE 15. OUTPUT SATURATION CURRENTS AS A FUNCTION OF THRESHOLD VOLTAGE
1.17 IO = 1mA, VOUT = 5V IHYS = -7A, VHYS = 0V
1.18
1.17 THRESHOLD VOLTAGE 1.16 THRESHOLD VOLTAGE
1.16 BOTH OUTPUT AND HYSTERESIS OUTPUT
1.15
1.15
BOTH OUTPUT AND HYSTERESIS OUTPUT
1.14
TA = +25oC IOUT = 4mA, VOUT = 1V IHYS = -7A, VHYS = (V+ -2) V 1 2 3 45 10 20 30 4050
1.14 -55
1.13 -25 +5 +35 +65 +95 +125 TEMPERATURE (oC) SUPPLY VOLTAGE
FIGURE 16. THRESHOLD VOLTAGE TO TURN OUTPUTS "JUST ON" AS A FUNCTION OF TEMPERATURE
FIGURE 17. THRESHOLD VOLTAGE TO TURN OUTPUTS "JUST ON" AS A FUNCTION OF SUPPLY VOLTAGE
7-167
ICL8211, ICL8212 Typical Performance Curves
(ICL8212 ONLY) (Continued)
0.6 OUTPUT SAT. CURRENT (VO = 4.0V)
Detailed Description
The ICL8211 and ICL8212 use standard linear bipolar integrated circuit technology with high value thin film resistors which define extremely low value currents. Components Q1 through Q10 and R1, R2 and R3 set up an accurate voltage reference of 1.15V. This reference voltage is close to the value of the bandgap voltage for silicon and is highly stable with respect to both temperature and supply voltage. The deviation from the bandgap voltage is necessary due to the negative temperature coefficient of the thin film resistors (-5000 ppm per oC). Components Q2 through Q9 and R2 make up a constant current source; Q2 and Q3 are identical and form a current mirror. Q8 has 7 times the emitter area of Q9, and due to the current mirror, the collector currents of Q8 and Q9 are forced to be equal and it can be shown that the collector current in Q8 and Q9 is
IC (Q8 or Q9) = 1 R2 x kT q In7
OUTPUT SATURATION VOLTAGE
0.5
0.4 VOLTAGE SAT. CURRENT (IO = 10mA)
0.3
0.2
0.1
V+ = +5V VTH = 1.2V -25 +5 +35 +65 +95 +125
0 -55
TEMPERATURE (oC)
FIGURE 18. OUTPUT SATURATION VOLTAGE AND CURRENT AS A FUNCTION OF TEMPERATURE
40 TA = +25oC V+ = +5V VTH =1.25V OUTPUT CURRENT (mA) 30
or approximately 1A at +25oC
Where k = Boltzman's Constant q = Charge on an Electron and T = Absolute Temperature in oK
20 VTH = 1.158V 10
Transistors Q5, Q6, and Q7 assure that the VCE of Q3, Q4, and Q9 remain constant with supply voltage variations. This ensures a constant current supply free from variations. The base current of Q1 provides sufficient start up current for the constant source; there being two stable states for this type of circuit - either ON as defined above, or OFF if no start up current is provided. Leakage current in the transistors is not sufficient in itself to guarantee reliable startup. Q4 is matched to Q3 and Q2; Q10 is matched to Q9. Thus the IC and VBE of Q10 are identical to that of Q9 or Q8. To generate the bandgap voltage, it is necessary to sum a voltage equal to the base emitter voltage of Q9 to a voltage proportional to the difference of the base emitter voltages of two transistors Q8 and Q9 operating at two current densities.
Thus 1.5 = VBE (Q9 or Q10) + R3 R2 R3 R2 x kT q
VTH = 1.153V 0 0.1 1.0 10.0 OUTPUT VOLTAGE 30.0 100.0
FIGURE 19. OUTPUT CURRENT AS A FUNCTION OF OUTPUT VOLTAGE
0 HYSTERESIS OUTPUT CURRENT (A) -5 -10 VT = 1.153V -15 -20 -25 -30 -35 -40 -10.00 TA = +25oC V+ = +10V -1.00 -0.10 -0.01 HYSTERESIS OUTPUT VOLTAGE VT = 1.18V VT = 1.152V
which provides:
= 12 (approximately.)
The total supply current consumed by the voltage reference section is approximately 6A at room temperature. A voltage at the THRESHOLD input is compared to the reference 1.15V by the comparator consisting of transistors Q11 through Q17. The outputs from the comparator are limited to two diode drops less than V+ or approximately 1.1V. Thus the base current into the hysteresis output transistor is limited to about 500nA and the collector current of Q19 to 100A. In the case of the ICL8211, Q21 is proportioned to have 70 times the emitter area of Q20 thereby limiting the output current to approximately 7mA, whereas for the ICL8212
FIGURE 20. HYSTERESIS OUTPUT CURRENT AS A FUNCTION OF HYSTERESIS OUTPUT VOLTAGE
7-168
ICL8211, ICL8212
almost all the collector current of Q19 is available for base drive to Q21, resulting in a maximum available collector current of the order of 30mA. It is advisable to externally limit this current to 25mA or less. as TTL or CMOS using a single pullup resistor. There is a guaranteed TTL fanout of 2 for the ICL8211 and 4 for the ICL8212. A principal application of the ICL8211 is voltage level detection, and for that reason the OUTPUT current has been limited to typically 7mA to permit direct drive of an LED connected to the positive supply without a series current limiting resistor. On the other hand the ICL8212 is intended for applications such as programmable zener references, and voltage regulators where output currents well in excess of 7mA are desirable. Therefore, the output of the ICL8212 is not current limited, and if the output is used to drive an LED, a series current limiting resistor must be used. In most applications an input resistor divider network may be used to generate the 1.15V required for VTH. For high accuracy, currents as large as 50A may be used, however for those applications where current limiting may be desirable, (such as when operating from a battery) currents as low as 6mA may be considered without a great loss of accuracy. 6mA represents a practical minimum, since it is about this level where the device's own input current becomes a significant percentage of that flowing in the divider network.
V+ 1 2 VTH 3 VO VHYST RL2 VO2 VO1 4 6 5 CMOS OR TTL GATES 8 7 PULLUP RESISTOR
Applications
The ICL8211 and ICL8212 are similar in many respects, especially with regard to the setup of the input trip conditions and hysteresis circuitry. The following discussion describes both devices, and where differences occur they are clearly noted.
General Information
Threshold Input Considerations Although any voltage between -5V and V+ may be applied to the THRESHOLD terminal, it is recommended that the THRESHOLD voltage does not exceed about +6V since above that voltage the threshold input current increases sharply. Also, prolonged operation above this voltage will lead to degradation of device characteristics. The outputs change states with an input THRESHOLD voltage of approximately 1.15V. Input and output waveforms are shown in Figure 21 for a simple 1.15V level detector.
INPUT VOLTAGE (RECOMMENDED RANGE -5 TO +5V) V+ 1 2 VTH 3 4 8 7 6 5 RL1 (V+ MUST BE EQUAL OR EXCEED 1.8V)
FIGURE 22. OUTPUT LOGIC INTERFACE
INPUT 1 2 0 VTH 3 4 8 7 6 5
V+
1.15V
R2
V+ 0V V+ 0V ICL8212 OUTPUT ICL8211 OUTPUT V-
R1
FIGURE 21. VOLTAGE LEVEL DETECTION
FIGURE 23. INPUT RESISTOR NETWORK CONSIDERATIONS
The HYSTERESIS output is a low current output and is intended primarily for input threshold voltage hysteresis applications. If this output is used for other applications it is suggested that output currents be limited to 10A or less. The regular OUTPUT's from either the ICL8211 or ICL8212 may be used to drive most of the common logic families such
Case 1. High accuracy required, current in resistor network unimportant Set I = 50A for VTH = 1.15V R1 20k Case 2. Good accuracy required, current in resistor network important Set I = 7.5A for VTH = 1.15V R1 150k
7-169
ICL8211, ICL8212
INPUT 1 2 INPUT VOLTAGE R1 V3 4 8 7 6 5 V+
R2
The disadvantage of the simple detection circuits is that there is a small but finite input range where the outputs are neither totally `ON' nor totally `OFF'. The principle behind hysteresis is to provide positive feedback to the input trip point such that there is a voltage difference between the input voltage necessary to turn the outputs ON and OFF. The advantage of hysteresis is especially apparent in electrically noisy environments where simple but positive voltage detection is required. Hysteresis circuitry, however, is not limited to applications requiring better noise performance but may be expanded into highly complex systems with multiple voltage level detection and memory applicationsrefer to specific applications section. There are two simple methods to apply hysteresis to a circuit for use in supply voltage level detection. These are shown in Figure 27. The circuit of Figure 27A requires that the full current flowing in the resistor network be sourced by the HYSTERESIS output, whereas for circuit Figure 27B the current to be sourced by the HYSTERESIS output will be a function of the ratio of the two trip points and their values. For low values of hysteresis, circuit Figure 27B is to be preferred due to the offset voltage of the hysteresis output transistor. A third way to obtain hysteresis (ICL8211 only) is to connect a resistor between the OUTPUT and the THRESHOLD terminals thereby reducing the total external resistance between the THRESHOLD and GROUND when the OUTPUT is switched on.
Input voltage to change to output states (R1 + R2) = x 1.15V R1 FIGURE 24. RANGE OF INPUT VOLTAGE GREATER THAN +1.15 VOLTS
Setup Procedures For Voltage Level Detection Case 1. Simple voltage detection no hysteresis Unless an input voltage of approximately 1.15V is to be detected, resistor networks will be used to divide or multiply the unknown voltage to be sensed. Figure 25 shows procedures on how to set up resistor networks to detect INPUT VOLTAGES of any magnitude and polarity.
VREF (+VE) MAY BE ANY STABLE VOLTAGE VOLTAGE REFERENCE GREATER THAN 1.15V 1 2 3 4 8 7 6 5
V+
R2
R1
Practical Applications
Low Voltage Battery Indicator (Figure 28) This application is particularly suitable for portable or remote operated equipment which requires an indication of a depleted or discharged battery. The quiescent current taken by the system will be typically 35A which will increase to 7mA when the lamp is turned on. R3 will provide hysteresis if required. Nonvolatile Low Voltage Detector (Figure 29) In this application the high trip voltage VTR2 is set to be above the normal supply voltage range. On power up the initial condition is A. On momentarily closing switch S1 the operating point changes to B and will remain at B until the supply voltage drops below VTR1, at which time the output will revert to condition A. Note that state A is always retained if the supply voltage is reduced below VTR1 (even to zero volts) and then raised back to VNOM. Nonvolatile Power Supply Malfunction Recorde (Figure 30 and Figure 31) In many systems a transient or an extended abnormal (or absence of a) supply voltage will cause a system failure. This failure may take the form of information lost in a volatile semiconductor memory stack, a loss of time in a timer or even possible irreversible damage to components if a supply voltage exceeds a certain value. It is, therefore, necessary to be able to detect and store the fact that an out-of-operating range supply voltage condition has occurred, even in the case where a supply voltage may
Range of input voltage less than +1.15V Input voltage to change the output states R2VREF (R1 + R2) x 1.15 = R1 R1 FIGURE 25. INPUT RESISTOR NETWORK SETUP PROCEDURES
For supply voltage level detection applications the input resistor network is connected across the supply terminals as shown in Figure 26.
V+ 1 2 3 4 R1 VO 8 7 6 5 INPUT VOLTAGE OR SUPPLY VOLTAGE
R2
FIGURE 26. COMBINED INPUT AND SUPPLY VOLTAGES
Case 2. Use of the HYSTERESIS function
7-170
ICL8211, ICL8212
V+ R3 1 R2 2 3 4 R1 VO 8 7 6 5 150k R2 R3 (NOTE 1)
1 2 3 4 ICL8211
8 7 6 5 LED LAMP
Low trip voltage VTR1 = (R1 + R2) x 1.15 + 0.1V R1 (R1 + R2 + R3) R1 FIGURE 27A.
V+ RQ RS
NOTE 1. R3 OPTIONAL
FIGURE 28. LOW VOLTAGE BATTERY INDICATOR volts
High trip voltage VTR2 = x 1.15V
V+ S1
1 2 3 4 FIG 7
8 7 6 5 VO
R3
1 2
8 7 6 5 OUTPUT RL
R2
3 4
RP
R1
Low trip voltage RQRS + RP VTR1 = (RQ + RS) High trip voltage VTR2 = (RP + RQ) RP x 1.15V
1 x RP
x 1.15V
FIGURE 29A.
FIGURE 27B.
ICL8212 OUTPUT STATE
B OFF ON
ICL8211 OUTPUT STATE
OFF
ON
ON
OFF
ON A
OFF
VTR1 SUPPLY VOLTAGE
VTR2
VTR1
VNOM
VTR2
SUPPLY VOLTAGE
FIGURE 27C. FIGURE 27. TWO ATERNATIVE VOLTAGE DETECTION CIRCUITS EMPLOYING HYSTERESIS TO PROVIDE PAIRS OF WELL DEFINED TRIP VOLTAGES
FIGURE 29B. FIGURE 29. NON-VOLATILE LOW VOLTAGE INDICATOR
7-171
ICL8212 OUTPUT STATE
ICL8211 OUTPUT STATE
ICL8211, ICL8212
have dropped to zero. Upon power up to the normal operating voltage this record must have been retained and easily interrogated. This could be important in the case of a transient power failure due to a faulty component or intermittent power supply, open circuit, etc., where direct observation of the failure is difficult. A simple circuit to record an out of range voltage excursion may be constructed using an ICL8211, an ICL8212 plus a few resistors. This circuit will operate to 30V without exceeding the maximum ratings of the ICs. The two voltage limits defining the in range supply voltage may be set to any value between 2.0V and 30V. The ICL8212 is used to detect a voltage, V2, which is the upper voltage limit to the operating voltage range. The ICL8211 detects the lower voltage limit of the operating voltage range, V1. Hysteresis is used with the ICL8211 so that the output can be stable in either state over the operating voltage range V1 to V2 by making V3 - the upper trip point of the ICL8211 much higher in voltage than V2. The output of the ICL8212 is used to force the output of the ICL8211 into the ON state above V2. Thus there is no value of the supply voltage that will result in the output of the ICL8211 changing from the ON state to the OFF state. This may be achieved only by shorting out R3 for values of supply voltage between V1 and V2. Constant Current Sources (Figure 32) The ICL8212 may be used as a constant current source of value of approximately 25A by connecting the THRESHOLD terminal to GROUND. Similarly the ICL8211 will provide a 130A constant current source. The equivalent parallel resistance is in the tens of megohms over the supply voltage range of 2V to 30V. These constant current sources may be used to provide basing for various circuitry including differential amplifiers and comparators. See Typical Operating Characteristics for complete information. Programmable Zener Voltage Reference (Figure 33) The ICL8212 may be used to simulate a zener diode by connecting the OUTPUT terminal to the VZ output and using a resistor network connected to the THRESHOLD terminal to program the zener voltage
VZENER = (R1 + R2) R1 x 1.l5V.
V+ R3 R4 1 2 3 4 R5 ICL8212 8 7 6 5 R2 S1 RESET
1 2 3 4 ICL8211
8 7 6 5 OUTPUT R6
R1
FIGURE 30. NON-VOLATILE POWER SUPPLY MALFUNCTION RECORDER
OUTPUT ICL8211 ICL8212 DISCONNECTED
OUTPUT ICL8212
OUTPUT ICL8211 AS PER FIGURE 7
VNOM
VNOM
OFF
OFF
OFF
ON
ON
ON
V1 SUPPLY VOLTAGE
V2
V3
V2 SUPPLY VOLTAGE
V1
V2
SUPPLY VOLTAGE
FIGURE 31. OUTPUT STATES OF THE ICL8211 AND ICL8212 AS A FUNCTION OF THE SUPPLY VOLTAGE
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ICL8211, ICL8212
Since there is no internal compensation in the ICL8212 it is necessary to use a large capacitor across the output to prevent oscillation. Zener voltages from 2V to 30V may be programmed and typical impedance values between 300A and 25A will range from 4 to 7. The knee is sharper and occurs at a significantly lower current than other similar devices available.
V+ 1 8 7 6 5
This regulator may be used with lower input voltages than most other commercially available regulators and also consumes less power for a given output control current than any commercial regulator. Applications would therefore include battery operated equipment especially those operating at low voltages. High Supply Voltage Dump Circuit (Figure 35) In many circuit applications it is desirable to remove the power supply in the case of high voltage overload. For circuits consuming less than 5mA this may be achieved using an ICL8211 driving the load directly. For higher load currents it is necessary to use an external pnp transistor or darlington pair driven by the output of the ICL8211. Resistors R1 and R2 set up the disconnect voltage and R3 provides optional voltage hysteresis if so desired.
V+ R2 R3 1 2 3 4 R1 ICL8211 8 7 6 5 V+ CIRCUIT BEING PROTECTED V-
=
I 1 2 3 4 8 7 6 5
OR
2 3 4
I I = 25A (ICL8212) I = 130A (ICL8211)
FIGURE 32. CONSTANT CURRENT SOURCE APPLICATIONS
6 5 V+ ZENER VOLTAGE 4 3 V+ ICL 8212 VTH
150K R1 500K
V(a) V+ R2 VZENER R2 1 2 R3 3 4 R1 ICL8211 8 7 6 5 V+ CIRCUIT BEING PROTECTED VR4
IS
2 1
+ -
5F
OUT
0 0.01 0.1 1.0 SUPPLY CURRENT (mA) 10 100 V(b)
FIGURE 33. PROGRAMMABLE ZENER VOLTAGE REFERENCE
FIGURE 35. HIGH VOLTAGE DUMP CIRCUITS
Precision Voltage Regulator (Figure 34) The ICL8212 may be used as the controller for a highly stable series voltage regulator. The output voltage is simply programmed, using a resistor divider network R1 and R2. Two capacitors C1 and C2 are required to ensure stability since the ICL8212 is uncompensated internally.
V+ 1 UNREG2 ULATED DC SUPPLY 3 4 ICL8212 8 7 6 5 R1 C1 C2 R3 Q1 R2 V+
Frequency Limit Detector (Figure 36) Simple frequency limit detectors providing a GO/NO-GO output for use with varying amplitude input signals may be conveniently implemented with the ICL8211/8212. In the application shown, the first ICL8212 is used as a zero crossing detector. The output circuit consisting of R3, R4 and C2 results in a slow output positive ramp. The negative range is much faster than the positive range. R5 and R6 provide hysteresis so that under all circumstances the second ICL8212 is turned on for sufficient time to discharge C3. The time constant of R7 C3 Is much greater than R4 C2. Depending upon the desired output polarities for low and high input frequencies, either an ICL8211 or an ICL8212 may be used as the output driver. This circuit is sensitive to supply voltage variations and should be used with a stabilized power supply. At very low frequencies the output will switch at the input frequency. Switch Bounce Filter (Figure 37) Single pole single throw (SPST) switches are less costly and more available than single pole double throw (SPDT) switches.
VOUT =
R2 + R1 x 1.15V R1
FIGURE 34. PRECISION VOLTAGE REGULATOR
7-173
ICL8211, ICL8212
SPST switches range from push button and slide types to calculator keyboards. A major problem with the use of switches is the mechanical bounce of the electrical contacts on closure. Contact bounce times can range from a fraction of a millisecond to several tens of milliseconds depending upon the switch type. During this contact bounce time the switch may make and break contact several times. The circuit shown in Figure 37 provides a rapid charge up of C1 to close to the positive supply voltage (V1) on a switch closure and a corresponding slow discharge of C1 on a switch break. By proportioning the time constant of R1 C1 to approximately the manufacturer's bounce time the output as terminal #4 of the ICL8211/8212 will be a single transition of state per desired switch closure Low Voltage Power Disconnect (Figure 38) There are some classes of circuits that require the power supply to be disconnected if the power supply voltage falls below a certain value. As an example, the National LM199 precision reference has an on chip heater which malfunctions with supply voltages below 9V causing an excessive device temperature. The ICL8212 may be used to detect a power supply voltage of 9V and turn the power supply off to the LM199 heater section below that voltage. For further applications, see AN027 "Power Supply Design using the ICL8211 and ICL8212."
V+ 1 C1 INPUT R2 R1 4 R3 C2 C3 OUTPUT 5 4 5 4 5 2 3 ICL8212 8 7 6 A R5 3 R4 1 R6 2 ICL8212 8 7 6 B R7 1 2 3 ICL8211 OR ICL8212 #3 8 7 6 R6
TIME CONSTANT R3C2 < R4C2 R7C3 VARY R1 FOR OPTION ZERO CROSSING DETECTION VARY R4 TO SET DETECTION FREQUENCY
INPUT OFF OUTPUT STATE ICL8211 1.15V A ON TIME #2
INDETERMINATE BELOW FO ON OUTPUT STATE ICL8212 ON OFF FO FREQUENCY V500k 1 2 RL 3 4 56k VO ICL8212 8 7 6 5 3.9k LM199 4.7k OUTPUT REFERENCE
1.15V B
FIGURE 36. FREQUENCY LIMIT DETECTOR
V+ R4 R2 100 1 2 3 4 R3 R1 C1 ICL8211 OR ICL8212 8 7 6 5
FIGURE 37. SWITCH BOUNCE FILTER
FIGURE 38. LOW VOLTAGE POWER SUPPLY DISCONNECT
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