MICREL MIC833_02

MIC833
Micrel
MIC833
Comparator and Reference with Adj. Hystersis
Final Information
General Description
Features
The MIC833 is a micropower precision dual voltage comparator with an on-chip reference and latch.
• Optimized for PDAs, cellular telephones, pagers,
and other battery-powered devices
• Inputs and output can pulled up to 6V
regardless of supply voltage
• Independently adjustable high- and
low-voltage thresholds
• High ±1.5% voltage threshold accuracy
• Extremely low 1µA typical supply current
• Immune to brief input transients
• 5-lead SOT-23 package
High- and low-voltage thresholds are adjusted independently, allowing for wide hysteresis. Three external resistors
determine the threshold voltages. Voltage detection thresholds are accurate to 1.5%.
Supply current is extremely low (1µA, typical), making it ideal
for portable applications.
The MIC833 is supplied in Micrel’s IttyBitty™ 5-lead SOT-235 package.
See the MIC2778 for applications requiring an output delay.
Applications
•
•
•
•
•
•
PDAs
Pagers
Cordless phones
Consumer electronics
Embedded controllers
Personal electronics
Ordering Information
Part Number
Marking
Accuracy
Temperature Range
Package
MIC833BM5
B11
1.5%
–40°C to +85°C
SOT-23-5
Typical Application
VIN VDD
VPULL-UP
MIC833
R1
5
3
R2
1
VDD
OUT
4
LTH
HTH
GND
R3
2
RPU
VOUT
VLTH > VHTH
VREF = 1.24V
VLTH(max) = VHTH(max) = 6V
VPULL-UP(max) = 6V
1.5V ≤ VDD ≤ 5.5V
IttyBitty™ is a trademark of Micrel, Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
September 2001
1
MIC833
MIC833
Micrel
Pin Configuration
LTH GND HTH
3
2
1
4
5
OUT
VDD
SOT-23-5 (M5)
Pin Description
Pin Number
Pin Name
1
HTH
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.
2
GND
Ground
3
LTH
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.
4
OUT
Output: Active-high, open-drain output. This output is de-asserted and
latched when VLTH <VREF, indicating a low voltage condition. This state
remains latched until VHTH > VREF.
5
VDD
Power Supply (Input): Independent supply input for internal circuitry.
MIC833
Pin Function
2
September 2001
MIC833
Micrel
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (VDD) ..................................... –0.3V to +7V
Input Voltages (VLTH, VHTH) .......................................... +7V
Output Current (IOUT) ................................................. 20mA
Storage Temperature (TS) ....................... –65°C to +150°C
ESD Rating, Note 3 ...................................................... 2kV
Supply Voltage (VDD) .................................. +1.5V to +5.5V
Input Voltage (VLTH, VHTH) ............................ –0.3V to +6V
Ambient Temperature Range (TA) ............. –40°C to +85°C
Junction Temperature (TJ) ....................... Internally Limited
Package Thermal Resistance (θJA) ...................... 260°C/W
Electrical Characteristics
1.5V ≤ VDD ≤ 5.5V; TA = +25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Symbol
Parameter
Condition
IDD
Supply Current
outputs not asserted
ILTH, IHTH
Input Leakage Current
VREF
Reference Voltage
tD
Propagation Delay
VOUT
Min
1.221
Output Voltage-Low, Note 4
Typ
Max
Units
1
2
µA
0.005
10
nA
1.240
1.259
V
VLTH = 1.352V to 1.128V
5
µs
VHTH = 1.128V to 1.352V
5
µs
OUT de-asserted, ISINK = 1.6mA, VDD ≥ 1.6V
0.3
V
OUT de-asserted, ISINK = 100µA, VDD ≥ 1.2V
0.4
V
Note 1.
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
Note 4.
VDD operating range is 1.5V to 5.5V. output is guaranteed to be held low down to VDD = 1.2V.
Functional Diagram
Note A
VHI
VIN
V
(Note B) LO
Note A
VPULL-UP
VOUT
0V
Note A. Brief transients are ignored by the MIC833. See “Applications Information.”
Note B. VLTH > VLO >VREF.
Timing Diagram
VLTH
VREF + 100mV
Inputs
VREF
VREF – 100mV
VHTH
tD
tD
VPULL-UP
VOUT
0V
September 2001
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MIC833
MIC833
Micrel
Block Diagram
VDD
+1.5V to +5.5V
5
VDD
VIN
Low-Voltage
Detect
LTH
VLTH
3
R Q
High-Voltage
Detect
HTH
VHTH
OUT
4
S Q
1
1.24V
Bandgap
Reference
MIC833
2
GND
Trip Points
Input voltage is monitored by the comparators via a voltage
divider network. The divided voltage is compared to an
internal reference voltage. When the voltage at the LTH input
pin drops below the internal reference voltage, the output
pulls low. Because of the voltage divider, the voltage at HTH
is assured to be below the reference voltage.
Functional Description
The MIC833 monitors a voltage and detects when it is below
or above two independently programmed levels.
Voltage Low Output
The output (OUT) is an active-high, open-drain output which
sinks current when the MIC833 detects a low input voltage at
its LTH input. This condition is latched until the HTH input is
presented with a voltage higher than the internal VREF
(+1.24V).
MIC833
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September 2001
MIC833
Micrel
drain to 3.1V. Using 3.1V for the VIN(lo) threshold allows
calculation of the two remaining resistor values.
Applications Information
Output
Since the MIC833 output is an open-drain MOSFET, most
applications will require a pull-up resistor. The value of the
resistor should not be too large or leakage effects may
dominate. 470kΩ is the maximum recommended value. Note
that the output may be pulled up as high as 6V regardless of
IC supply voltage. See “Electrical Characteristics.”
 1MΩ 
VIN(lo) = 3.1V = 1.24 

 R2 + 344k 
R2 = 56kΩ
1MΩ − (R2 − R3) = R1
R1 = 600kΩ
The accuracy of the resistors can be chosen based upon the
accuracy required by the system.
Programming the Thresholds
The low-voltage threshold is calculated using:
 R1 + R2 + R3 
VIN(lo) = VREF 

 R2 + R3 
The inputs may be subjected to voltages as high as 6V steady
state without adverse effects of any kind, regardless of the IC
supply voltage. This applies even if the supply voltage is zero.
This permits the situation in which the IC supply is turned off,
but voltage is still present on the inputs. See “Electrical
Characteritics.”
The high-voltage threshold is calculated using:
 R1 + R2 + R3 
VIN(hi) = VREF 



R3
Input Transients
The MIC833 is inherently immune to very short negativegoing “glitches.” Very brief transients may exceed the VIN(lo)
threshold without tripping the output.
where, for both equations:
VREF = 1.240V
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 1MΩ for RTOTAL is a reasonable value
because it draws minimum current but has no significant
effect on accuracy.
As shown in Figure 2, the narrower the transient, the deeper
the threshold overdrive that will be ignored by the MIC833.
The graph represents the typical allowable transient duration
for a given amount of threshold overdrive that will not toggle
the output.
VIN
R1
MAX. TRANSIENT DURATION (µs)
When working with large resistors, a small amount of leakage
current can cause voltage offsets that degrade system accuracy. The maximum recommended total resistance from VIN
to ground is 3MΩ.
VDD
604k
1%
R2
56k
1%
R3
340k
1%
MIC833
5
3
1
VDD
OUT
4
470k
VOUT
LTH
HTH
GND
2
Input Transient
Response
140
120
100
80
60
40
20
0
1
10
100
1000
RESET COMP. OVERDRIVE, VREF–VLTH (mV)
Figure 2. Input Transient Response
Initialization Behavior
When the MIC833 is powered up, the comparators and latch
become active before the reference voltage reaches its final
value. In most applications, this presents no problems. However, the user should be aware of this: when applying power
to the part, if the input voltage is between the two thresholds,
the output of the part will be high because input HTH will have
been higher than the 1.24V reference during initialization.
Figure 1. Example Circuit
Once the desired trip points are determined, set the VIN(hi)
threshold first.
For example, use a total of 1MΩ = 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:
VIN(hi)
It is not very likely the part would be powered up in this state;
it is more likely the same power supply will power the part and
develop its inputs. However, if the above-described condition
should occur, the next HTH threshold crossing would not be
processed; that is, the latch would have been already set. The
next valid input condition would have to be a crossing of the
LTH threshold, which resets the latch, after which “normal”
operation is restored.
 1MΩ 
= 3.6V = 1.24 

 R3 
R3 = 344kΩ
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
September 2001
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MIC833
MIC833
Micrel
Example Application
The battery charger of Figure 3 uses the MIC833 to detect a
low-battery voltage condition (VDIS) and enables a constantcurrent source (ICHG). Charging current is enabled until a
charged-battery voltage condition (VCHG) is detected; at
which time the charging-current source is disabled.
The circuitry of Figure 3 is deliberately generalized to imply
flexibility of application. Depending on the application, it may
not be possibly to power the MIC833 from the charger supply
voltage, see Note 2. It may be necessary to provide a
separate voltage regulator, or a resistive voltage divider to
reduce the VDD applied to the MIC833. The part can be
supplied by the battery voltage (VBAT) if this voltage is never
lower than 1.5V, the minimum operating VDD of the part.
Diode D1 was added to Figure 3 to ensure the disabled
current source does not draw battery current. Whether or not
D1 is required is a function of the output stage of the current
source and how it is disabled.
Charger
Supply
Voltage
Voltage thresholds, VDIS and VCHG, are programmed as
described in the appropriate above paragraph.
Constant-Current
Source
Note 1
IN
OUT
D1
EN
GND
Battery
R4
100k
Note 2
VBATT
(to load)
MIC833
OUT
VDD
LTH
HTH
VDIS
R2
0.1µF
GND
VCHG
R3
Note 1. D1 may not be required.
It is shown here to
indicate the disabled
current source should
not load the battery.
Note 2. VDD of the MIC833 is
limited to 5.5V maximum.
The part can be powered
by VBAT if the battery is
never discharged below
VDD(min) = 1.5V
Figure 3. Battery Charger
MIC833
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September 2001
MIC833
Micrel
Package Information
1.90 (0.075) REF
0.95 (0.037) REF
1.75 (0.069)
1.50 (0.059)
3.00 (0.118)
2.60 (0.102)
DIMENSIONS:
MM (INCH)
3.02 (0.119)
2.80 (0.110)
0.50 (0.020)
0.35 (0.014)
1.30 (0.051)
0.90 (0.035)
0.20 (0.008)
0.09 (0.004)
10°
0°
0.15 (0.006)
0.00 (0.000)
0.60 (0.024)
0.10 (0.004)
5-Pin SOT (M)
September 2001
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MIC833
MIC833
Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
USA
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 2001 Micrel Incorporated
MIC833
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September 2001