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MIC841/2
Micrel
MIC841/842
Comparator with Reference
General Description
The MIC841 and MIC842 are micropower, precision voltage comparators with an on-chip voltage reference. Both devices are intended for voltage monitoring applications. External resistors are used to set the voltage monitor threshold. When the threshold is crossed, the outputs switch polarity. The MIC842 incorporates a voltage reference and comparator with fixed internal hysteresis; two external resistors are used to set the switching threshold voltage. The MIC841 provides a similar function with user adjustable hysteresis; this part requires three external resistors to set the upper and lower thresholds (the difference between the threshold voltages being the hysteresis voltage). Both the MIC841 and MIC842 are available with push-pull or open-drain output stage. The push-pull output stage is configured either active high or active low; the open-drain output stage is only configured active high. Supply current is extremely low (1.5A, typical), making it ideal for portable applications. The MIC841/2 is supplied in Micrel's TeenyTM 5-lead SC-70 package. Data sheets and support documentation can be found on Micrel's web site at www.micrel.com.
TeenyTM
Features
* Optimized for PDAs, cellular telephones, pagers, and other battery-powered devices * Output can be pulled up to 6V regardless of supply voltage (841NBC5 only) * High 1.25% voltage threshold accuracy * Built in hysteresis for noise suppression (MIC842) * Extremely low 1.5A typical supply current * Immune to brief input transients * TeenyTM 5-lead SC-70 package
Applications
* * * * * * PDAs Pagers Cordless phones Consumer electronics Embedded controllers Personal electronics
Typical Application
VIN VDD MIC841 R1
5 3
VIN VDD
4
VDD LTH HTH
OUT GND
VOUT VLTH > V HTH VREF = 1.24V 1.5V V DD 5.5V
MIC842 R1
5
R2
1
2
VDD INP
OUT GND
4
VOUT VREF = 1.24V 1.5V VDD 5.5V
1
2
R3
R2
Threshold Detection with Hysteresis Set by a Third External Resistor
Threshold Detector with Internal Fixed Hysteresis
TeenyTM is a trademark of Micrel, Inc. Micrel, Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
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MIC841/2
MIC841/2
Micrel
Ordering Information
Part Number MIC841HBC5 MIC841LBC5 MIC841NBC5 MIC842HBC5 MIC842LBC5 MIC842NBC5 MIC841HYC5 MIC841LYC5 MIC841NYC5 MIC842HYC5 MIC842LYC5 MIC842NYC5 Marking B13 B14 B15 B16 B17 B18 B13 B14 B15 B16 B17 B18 Hysteresis Adjustment External External External Internal Internal Internal External External External Internal Internal Internal Output Stage Push Pull Push Pull Open Drain Push Pull Push Pull Open Drain Push Pull Push Pull Open Drain Push Pull Push Pull Open Drain Output Function Active High Active Low Active High Active High Active Low Active High Active High Active Low Active High Active High Active Low Active High Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package SC-70-5 SC-70-5 SC-70-5 SC-70-5 SC-70-5 SC-70-5 SC-70-5 Pb-Free SC-70-5 Pb-Free SC-70-5 Pb-Free SC-70-5 Pb-Free SC-70-5 Pb-Free SC-70-5 Pb-Free
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MIC841/2
Micrel
Pin Configuration
LTH GND HTH
3 2 1
NC GND INP
3 2 1
Bxx
4 5 4
Bxx
5
OUT
VDD
OUT
VDD
MIC841 SC-70-5 (C5)
MIC842 SC-70-5 (C5)
Pin Description MIC841
Pin Number 1 Pin Name HTH Pin Function High-Voltage Threshold (Input): Analog input to a comparator. This is the voltage input assigned to detect a high-voltage condition. When the level on this pin exceeds VREF, OUT is asserted and the condition is latched until VLTH < VREF. Ground. Low-Voltage Threshold (Input): Analog input to a comparator. This is the voltage input assigned to detect a low voltage condition. When the level on this pin falls below VREF, OUT is de-asserted and the condition is latched until VHTH > VREF. Output: Active-high, open-drain output. This output is de-asserted and latched when VLTH VREF. Output: Push-pull output. This output is de-asserted and latched when VLTH < VREF, indicating a low voltage condition. This state remains latched until VHTH > VREF. Output: Push-pull output. This output is asserted and latched when VLTH < VREF, indicating a low voltage condition. This state remains latched until VHTH > VREF. Power Supply (Input): Independent supply input for internal circuitry.
2 3
GND LTH
4
OUT ("N" Version)
OUT ("H" Version)
OUT ("L" Version)
5
VDD
Pin Description MIC842
Pin Number 1 2 3 4 Pin Name INP GND NC OUT ("N" Version) Pin Function Input: Analog input to the comparator. When VINP > VREF + VHYST, VOUT is asserted, and the condition is held until VINP < VREF. Ground. No Connect. Output: Active-high, open-drain output. This output is de-asserted when VINP < VREF, indicating a low voltage input. The output is asserted when VINP > VREF + VHYST. Output: Push-pull output. This output is de-asserted and latched when VINP < VREF, indicating a low voltage condition. This state remains latched until VINP > VREF + VHYST. Output: Push-pull output. This output is asserted and latched when VINP < VREF, indicating a low voltage condition. This state remains latched until VINP > VREF + VHYST. Power Supply (Input): Independent supply input for internal circuitry.
OUT ("H" Version)
OUT ("L" Version)
5
VDD
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MIC841/2
MIC841/2
Micrel
Absolute Maximum Ratings(1)
Supply Voltage (VDD) ..................................... -0.3V to +7V Input Voltage (VINP) ...................................................... +7V Output Current (IOUT) ................................................. 20mA Storage Temperature (TS) ....................... -65C to +150C ESD Rating, Note 3 ...................................................... 1kV
Operating Ratings(2)
Supply Voltage (VDD) .................................. +1.5V to +5.5V Input Voltage (VINP) ......................................... -0.3V to 6V Ambient Temperature Range (TA) ............. -40C to +85C Junction Temperature (TJ) ....................... Internally Limited Package Thermal Resistance (JA) ...................... 450C/W
Electrical Characteristics(4)
1.5V VDD 5.5V; TA = +25C, bold values indicate -40C TA +85C; unless noted. Symbol IDD IINP VREF VHYST tD VOUT (Note 6) Output Voltage-High Parameter Supply Current Input Leakage Current Reference Voltage 0C to 85C -40C to 85C Hysteresis Voltage, (Note 5) Propagation Delay MIC842 only VINP = 1.352V to 1.128V VINP = 1.143V to 1.367V Output Voltage-Low ISINK = 1.6mA, VDD 1.6V ISINK = 100A, VDD 1.2V ISOURCE = 500A, VDD 1.6V ISOURCE = 50A, VDD 1.2V
Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. 4. Specification for packaged product only. 5. VHTH = VREF + VHYST. 6. VDD operating range is 1.5V to 5.5V. Output is guaranteed to be de-asserted down to VDD = 1.2V.
Condition output not asserted
Min
Typ 1.5 0.005
Max 3 10 1.256 1.261 35
Units A nA V V mV s s
1.225 1.219 8
1.240 1.240 20 12 8 0.05 0.005 0.99VDD 0.99VDD
0.3 0.4
V V V V
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Block Diagrams
VDD
5
VIN
VDD
5
VDD
VIN Low-Voltage Detect
VDD
INP
LTH VLTH
3
High-Voltage Detect OUT
4
VTH
RQ High-Voltage Detect
4
1
OUT
HTH VHTH
1
SQ
1.24V Bandgap Reference
1.24V Bandgap Reference MIC841H
2
MIC842H
2
GND
GND
VDD
5
VIN Low-Voltage Detect LTH VLTH
3
VDD
VIN
VDD
5
VDD
INP
RQ High-Voltage Detect
4
High-Voltage Detect OUT
4
OUT
VTH
1
HTH VHTH
1
SQ
1.24V Bandgap Reference
1.24V Bandgap Reference MIC841L
2
MIC842L
2
GND
GND
VDD
5
VIN Low-Voltage Detect LTH VLTH
3
VDD
VIN
VDD
5
VDD
INP
RQ High-Voltage Detect SQ
4
High-Voltage Detect OUT
4
OUT
VTH
1
HTH VHTH
1
1.24V Bandgap Reference
1.24V Bandgap Reference MIC841N
2
MIC842N
2
GND
GND
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MIC841/2
MIC841/2
Micrel
Once the desired trip points are determined, set the VIN(HI) threshold first. For example, use a total of 1M = R1 + R2 + R3. For a typical single-cell lithium ion battery, 3.6V is a good "high threshold" because at 3.6V the battery is moderately charged. Solving for R3: 1M VIN(HI) = 3.6V = 1.24 R3
R3 = 344k Once R3 is determined, the equation for VIN(LO) can be used to determine R2. A single lithium-ion cell, for example, should not be discharged below 2.5V. Many applications limit the drain to 3.1V. Using 3.1V for the VIN(LO) threshold allows calculation of the two remaining resistor values.
Applications Information
Output The MIC841N and MIC842N outputs are an open-drain MOSFET, so most applications will require a pull-up resistor. The value of the resistor should not be too large or leakage effects may dominate. 470k is the maximum recommended value. Note that the output of "N" version may be pulled up as high as 6V regardless of the ICs supply voltage. The "H" and "L" versions of the MIC841 and MIC842 have a push-pull output stage, with a diode clamped to VDD. Thus, the maximum output voltage of the "H" and "L" versions is VDD. See "Electrical Characteristics." When working with large resistors on the input to the devices, a small amount of leakage current can cause voltage offsets that degrade system accuracy. The maximum recommended total resistance from VIN to ground is 3M. The accuracy of the resistors can be chosen based upon the accuracy required by the system. The inputs may be subjected to voltages as high as 6V steady-state without adverse effects of any kind regardless of the ICs supply voltage. This applies even if the supply voltage is zero. This permits the situation in which the IC's supply is turned off, but voltage is still present on the inputs. See "Electrical Characteristics." Programming the MIC841 Thresholds The low-voltage threshold is calculated using: VIN(LO) R1 + R2 + R3 = VREF R2 + R3
1M VIN(LO) = 3.1V = 1.24 R2 + 344k
R2 = 56k
1M - (R2 - R3) = R1
R1 = 600k The accuracy of the resistors can be chosen based upon the accuracy required by the system.
Programming the MIC842 Thresholds The voltage threshold is calculated using:
R1 + R2 VIN(LO) = VREF R2
The high-voltage threshold is calculated using: R1 + R2 + R3 VIN(HI) = VREF R3 where, for both equations:
VREF = 1.240V
where:
VREF = 1.240V
VIN
MIC842N R1
5
In order to provide the additional criteria needed to solve for the resistor values, the resistors can be selected such that they have a given total value, that is, R1 + R2 + R3 = RTOTAL. A value such as 1M for RTOTAL is a reasonable value because it draws minimum current but has no significant effect on accuracy.
VIN VDD
470k
4
VDD INP
OUT GND
VOUT
1
2
R2
Figure 2. MIC842 Example Circuit
MIC841N
5 3 1
R1
604k 1% 56k 1% 340k 1%
VDD LTH HTH
OUT GND
4
470k VOUT
2
R2
R3
In order to provide the additional criteria needed to solve for the resistor values, the resistors can be selected such that they have a given total value, that is, R1 + R2 = RTOTAL. A value such as 1M for RTOTAL is a reasonable value because it draws minimum current but has no significant effect on accuracy.
Figure 1. MIC841 Example Circuit
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Input Transients The MIC841/2 is inherently immune to very short negativegoing "glitches." Very brief transients may exceed the VIN(LO) threshold without tripping the output. As shown in Figure 3, the narrower the transient, the deeper the threshold overdrive that will be ignored by the MIC841/2. The graph represents the typical allowable transient duration for a given amount of threshold overdrive that will not generate an output.
MAX. TRANSIENT DURATION (s)
Micrel
140 120 100 80 60 40 20 0 1
Input Transient Response
10
100
1000
RESET COMP. OVERDRIVE, VREF-VLTH (mV)
Figure 3. Input Transient Response
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MIC841/2
MIC841/2
Micrel
Package Information
0.65 (0.0256) BSC
1.35 (0.053) 2.40 (0.094) 1.15 (0.045) 1.80 (0.071) 2.20 (0.087) 1.80 (0.071) DIMENSIONS: MM (INCH) 1.00 (0.039) 1.10 (0.043) 0.80 (0.032) 0.80 (0.032) 0.18 (0.007) 0.10 (0.004)
0.30 (0.012) 0.15 (0.006)
0.10 (0.004) 0.00 (0.000)
0.30 (0.012) 0.10 (0.004)
SC-70 (C5)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
USA
+ 1 (408) 944-0800
FAX
+ 1 (408) 474-1000
WEB
http://www.micrel.com
The information furnished by Micrel in this datasheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 2004 Micrel, Incorporated.
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