MIC834
Micrel
MIC834
Comparator with Reference
Final Information
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 1.5%.
Supply current is extremely low (1.5µA, typical), making it
ideal for portable applications.
The MIC834 is supplied in Micrel’s IttyBitty™ 5-lead SOT-23-
5 package.
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
±1.5%
voltage threshold accuracy
• Built in hysteresis for noise suppression
• Extremely low 1.5µA typical supply current
• Immune to brief input transients
• 5-lead SOT-23 package
Applications
•
•
•
•
•
•
PDAs
Pagers
Cordless phones
Consumer electronics
Embedded controllers
Personal electronics
Ordering Information
Part Number
MIC834BM5
Marking
B12
Accuracy
1.5%
Temperature Range
–40°C to +85°C
Package
SOT-23-5
Typical Application
V
IN
V
DD
MIC834
R1
5
V
PULL-UP
R
PU
4
VDD
INP
OUT
GND
V
OUT
V
REF
= 1.24V
V
INP(max)
= 6V
V
PULL-UP(max)
= 6V
1.5V
≤
V
DD
≤
5.5V
1
2
R2
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
MIC834
MIC834
Micrel
Pin Configuration
NC GND INP
3
2
1
4
5
OUT
VDD
SOT-23-5 (M5)
Pin Description
Pin Number
1
2
3
4
Pin Name
INP
GND
NC
OUT
Pin Function
Input: Analog input to the comparator. When V
INP
> V
REF
+ V
HYST
, V
OUT
is
asserted to a logic-high level output.
Ground
No Connect
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.
Power Supply (Input): Independent supply input for internal circuitry.
5
VDD
MIC834
2
September 2001
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 (θ
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
I
DD
I
INP
V
REF
V
HYST
t
D
V
OUT
Parameter
Supply Current
Input Leakage Current
Reference Voltage
Hysteresis Voltage,
Note 4
Propagation Delay
V
INP
= 1.352V to 1.128V
V
INP
= 1.143V to 1.367V
Output Voltage-Low,
Note 5
OUT de-asserted, I
SINK
= 1.6mA, V
DD
≥
1.6V
OUT de-asserted, I
SINK
= 100µA, V
DD
≥
1.2V,
Note 1.
Note 2.
Note 3.
Note 4.
Note 5.
Exceeding the absolute maximum rating may damage the device.
The device is not guaranteed to function outside its operating rating.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
V
HTH
= V
REF
+ V
HYST
.
V
DD
operating range is 1.5V to 5.5V. Output is guaranteed to be held low down to V
DD
= 1.2V.
Condition
output not asserted
Min
Typ
1.5
0.005
Max
3
10
1.259
35
Units
µA
nA
V
mV
µs
µs
1.221
10
1.240
23
12
8
0.05
0.005
0.3
0.4
V
V
Functional Diagram
V
IN
(Note A)
V
HTH
V
REF
0V
V
PULL-UP
V
OUT
0V
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.”
Note B
Note B
t
D
t
D
September 2001
3
MIC834
MIC834
Micrel
Block Diagram
V
IN
V
DD
5
VDD
INP
V
TH
1
High-Voltage
Detect
OUT
4
1.24V
Bandgap
Reference
MIC834
2
GND
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.
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.
MIC834
4
September 2001
MIC834
Micrel
V
IN
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. 470kΩ 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:
R1
+
R2
V
IN(lo)
=
V
REF
R2
where:
V
REF
=
1.240V
MIC834
R1
5
470k
4
VDD
INP
OUT
GND
V
OUT
1
2
R2
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.
MAX. TRANSIENT DURATION (µs)
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 1MΩ 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 3MΩ. 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.”
140
120
100
80
60
40
20
0
1
Input Transient
Response
10
100
1000
RESET COMP. OVERDRIVE, V
REF
–V
LTH
(mV)
Figure 2. Input Transient Response
September 2001
5
MIC834
嵌入式系统
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