April 2000
1
MIC834
MIC834
Micrel
MIC834
Comparator with Reference
Advance Information
Typical Application
INP
OUT
VDD
GND
MIC834
R
PU
V
IN
R1
R2
V
OUT
V
DD
V
PULL-UP
V
REF
= 1.24V
V
INP(max)
= 6V
V
PULL-UP(max)
= 6V
1.5V
V
DD
5.5V
4
2
1
5
Features
Optimized for PDAs, cellular telephones, pagers,
and other battery-powered devices
Input and output can be pulled up to 6V
regardless of supply voltage
High
1% voltage threshold accuracy
Built in hysteresis for noise suppression
Extremely low 1.5
A typical supply current
Immune to brief input transients
5-lead SOT-23 package
Applications
PDAs
Pagers
Cordless phones
Consumer electronics
Embedded controllers
Personal electronics
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
General Description
The MIC834 is a micropower, precision voltage comparator
with an on-chip voltage reference.
The threshold is adjusted by the choice of two external
resistors. Voltage detection threshold is accurate to 1%.
Supply current is extremely low (1.5
A, typical), making it
ideal for portable applications.
The MIC834 is supplied in Micrel's IttyBittyTM 5-lead SOT-23-
5 package.
IttyBittyTM is a trademark of Micrel, Inc.
Ordering Information
Part Number
Marking
Accuracy
Temperature Range
Package
MIC834BM5
B12
1%
40
C to +85
C
SOT-23-5
MIC834
Micrel
MIC834
2
April 2000
Pin Description
Pin Number
Pin Name
Pin Function
1
INP
Input: Analog input to the comparator. When V
INP
> V
REF
+ V
HYST
, V
OUT
is
asserted to a logic-high level output.
2
GND
Ground
3
NC
No Connect
4
OUT
Output: Active-high, open-drain output. This output is de-asserted when
V
INP
< V
REF
, indicating a low voltage input. The output is asserted when
V
INP
> V
REF
+ V
HYST.
5
VDD
Power Supply (Input): Independent supply input for internal circuitry.
Pin Configuration
INP
VDD
OUT
NC
1
3
4
5
2
GND
SOT-23-5 (M5)
April 2000
3
MIC834
MIC834
Micrel
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
DD
) ..................................... 0.3V to +7V
Input Voltage (V
INP
) ...................................................... +7V
Output Current (I
OUT
) ................................................. 20mA
Storage Temperature (T
S
) ....................... 65
C to +150
C
ESD Rating, Note 3 ...................................................... 2kV
Operating Ratings
(Note 2)
Supply Voltage (V
DD
) .................................. +1.5V to +5.5V
Input Voltage (V
INP
) ......................................... 0.3V to 6V
Ambient Temperature Range (T
A
) ............. 40
C to +85
C
Junction Temperature (T
J
) ....................... Internally Limited
Package Thermal Resistance (
JA
) ...................... 260
C/W
Electrical Characteristics
1.5V
V
DD
5.5V; T
A
= +25
C, bold values indicate 40
C
T
A
+85
C; unless noted
Symbol
Parameter
Condition
Min
Typ
Max
Units
I
DD
Supply Current
output not asserted
1.5
3
A
I
INP
Input Leakage Current
0.005
10
nA
V
REF
Reference Voltage
1.228
1.240
1.252
V
V
HYST
Hysteresis Voltage, Note 4
10
23
35
mV
t
D
Propagation Delay
V
INP
= 1.352V to 1.128V
12
s
V
INP
= 1.143V to 1.367V
8
s
V
OUT
Output Voltage-Low, Note 5
OUT de-asserted, I
SINK
= 1.6mA, V
DD
1.6V
0.05
0.3
V
OUT de-asserted, I
SINK
= 100
A, V
DD
1.2V,
0.005
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.
V
HTH
= V
REF
+ V
HYST
.
Note 5.
V
DD
operating range is 1.5V to 5.5V. Output is guaranteed to be held low down to V
DD
= 1.2V.
Functional Diagram
V
HTH
V
IN
(Note A)
0V
V
REF
Note B
Note B
V
PULL-UP
V
OUT
0V
t
D
t
D
Note A.
V
IN
here represents the attenuated input voltage, as applied to the INP pin; i.e., V
INP
.
Note B.
Brief transients are ignored by the MIC834. See "Applications Information."
MIC834
Micrel
MIC834
4
April 2000
Functional Description
The MIC834 monitors the input voltage and detects when it
is higher than a programmed level (plus V
HYST
). This condi-
tion asserts the active-high output. An external pull-up resis-
tor is used to produce a logic-one output. When the input
voltage falls below the programmed threshold (V
INP
< V
REF
),
the output stage is on.
Voltage Low Output
The voltage-low output (OUT) is an active-high, open-drain
output which sinks current when the MIC834 detects a low
input voltage.
Block Diagram
GND
V
IN
OUT
1.24V
Bandgap
Reference
High-Voltage
Detect
INP
V
TH
MIC834
4
2
1
5
VDD
V
DD
Trip Points
Input voltage is monitored by a comparator via a voltage
divider network. The divided voltage is compared to an
internal reference voltage. When the voltage at the input pin
INP exceeds the internal reference voltage (plus V
HYST
), the
output is pulled high by an external resistor.
V
HYST
is typically 23mV, and is added to the programmed
threshold voltage for positive-going inputs. Decreasing in-
puts trip at the user-programmed threshold voltage.
The tolerance of the switching threshold on the falling edge
is equal to the tolerance of just the voltage reference. The
tolerance of the switching threshold on the rising edge is
equal to the tolerance of the voltage reference
plus the
tolerance of the hysteresis voltage.
April 2000
5
MIC834
MIC834
Micrel
INP
OUT
VDD
GND
MIC834
470k
V
IN
R1
R2
V
OUT
4
2
1
5
Figure 1. Example Circuit
Input Transients
The MIC834 is inherently immune to very short negative-
going "glitches." Very brief transients may exceed the V
IN(lo)
threshold without tripping the output.
As shown in Figure 2, the narrower the transient, the deeper
the threshold overdrive that will be ignored by the MIC834.
The graph represents the typical allowable transient duration
for a given amount of threshold overdrive that will not gener-
ate an output.
0
20
40
60
80
100
120
140
1
10
100
1000
MAX. TRANSIENT DURATION (
s)
RESET COMP. OVERDRIVE, V
REF
V
LTH
(mV)
Input Transient
Response
Figure 2. Input Transient Response
Applications Information
Output
Since the MIC834 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. 470k
is the maximum recommended value. Note
that the output may be pulled up as high as 6V regardless of
the IC's supply voltage. See "Electrical Characteristics."
Programming the Threshold
The voltage threshold is calculated using:
V
V
R1 R2
R2
IN(lo)
REF
=
+
where:
V
1.240V
REF
=
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 = R
TOTAL
. A
value such as 1M
for R
TOTAL
is a reasonable value because
it draws minimum current but has no significant effect on
accuracy.
When working with large resistors, a small amount of leakage
current can cause voltage offsets that degrade system accu-
racy. The maximum recommended total resistance from V
IN
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
IC's 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."
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