Datasheet MIC833BM5 Datasheet (MICREL)

MIC833 Micrel

MIC833

Comparator and Reference with Adj. Hystersis

Advance Information

General Description

The MIC833 is a micropower precision dual voltage com­parator with an on-chip reference and latch.

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%.

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.

Ordering Information

Features

• 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% voltage threshold accuracy

• Extremely low 1µA typical supply current

• Immune to brief input transients

• 5-lead SOT-23 package

Applications

•PDAs

• Pagers

• Cordless phones

• Consumer electronics

• Embedded controllers

• Personal electronics

Typical Application

Part Number Marking Accuracy Temperature Range Package

MIC833BM5 B11 1% –40°C to +85°C SOT-23-5

V

R1

R2

R3

V

IN

DD

MIC833

5
3

LTH

1

HTH

OUTVDD

GND

V

PULL-UP

4

2

R

PU

V

LTH

V

REF

V

LTH(max)

V

PULL-UP(max)

1.5V ≤ V

V

OUT

> V

HTH

= 1.24V

= V

DD

HTH(max)

= 6V

≤ 5.5V

= 6V

IttyBitty™ is a trademark of Micrel, Inc.

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 [phone] • fax + 1 [phone] • http://www.micrel.com

January 2000 1 MIC833

MIC833 Micrel

Pin Configuration

GND

2

HTH

13

LTH

45

VDDOUT

SOT-23-5 (M5)

Pin Description

Pin Number Pin Name Pin Function

1 HTH High-Voltage Threshold (Input): Analog input to a comparator. This is the

2 GND Ground
3 LTH Low-Voltage Threshold (Input): Analog input to a comparator. This is the

4 OUT Output: Active-high, open-drain output. This output is de-asserted and

5 VDD Power Supply (Input): Independent supply input for internal circuitry.

voltage input assigned to detect a high-voltage condition when the level on
this pin exceeds V
V

LTH

< V

REF

.

, OUT is asserted and the condition is latched until

REF

voltage input assigned to detect a low voltage condition. When the level on
this pin falls below V
until V

latched when V

HTH

> V

REF

LTH

remains latched until V

, OUT is de-asserted and the condition is latched

REF

.

<V

, indicating a low voltage condition. This state

REF

HTH

> V

REF

.

MIC833 2 January 2000

MIC833 Micrel

Absolute Maximum Ratings (Note 1)

Supply Voltage (V
Input Voltages (V
Output Current (I

Storage Temperature (TS) ....................... –65°C to +150°C

ESD Rating, Note 3 ......................................................2kV

) ..................................... –0.3V to +7V

DD

, V

LTH

OUT

)..........................................+7V

HTH

).................................................20mA

Operating Ratings (Note 2)

Supply Voltage (V
Input Voltage (V
Ambient Temperature Range (T

Junction Temperature (TJ) ....................... Internally Limited

Package Thermal Resistance (θ

) .................................. +1.5V to +5.5V

DD

, V

LTH

) ............................ –0.3V to +6V

HTH

) .............–40°C to +85°C

A

) ......................260°C/W

JA

Electrical Characteristics

1.5V ≤ VDD ≤ 5.5V; TA = +25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Symbol Parameter Condition Min Typ Max Units

I

DD

I

LTH, IHTH

V

REF

t

D

V

OUT

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.

Supply Current outputs not asserted 1 2 µA
Input Leakage Current 0.005 10 nA
Reference Voltage 1.228 1.240 1.252 V
Propagation Delay V

Output Voltage-Low, Note 4 OUT de-asserted, I

= 1.352V to 1.128V 5 µs

LTH

V

= 1.128V to 1.352V 5 µs

HTH

= 1.6mA, VDD ≥ 1.6V 0.3 V

SINK

OUT de-asserted, I

= 100µA, VDD ≥ 1.2V 0.4 V

SINK

Functional Diagram

V

IN

V

V

PULL-UP

HI

LO

V

(Note B)

V

OUT

0V

Note A. Brief transients are ignored by the MIC833. See “Applications Information.”
Note B. V

> VLO >V

LTH

REF

.

Note A

Note A

Timing Diagram

V

LTHVHTH

Inputs

V

OUT

V

REF

V

REF

+ 100mV

V

REF

– 100mV

V

PULL-UP

0V

t

D

t

D

January 2000 3 MIC833

MIC833 Micrel

Block Diagram

V

DD

+1.5V to +5.5V

VDD

V

IN

Low-Voltage

Detect

5

LTH

HTH

LTH

HTH

3

High-Voltage

Detect

1

1.24V
Bandgap
Reference

2

GND

V

V

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 V
(+1.24V).

REF

RSQ

Q

MIC833

4

OUT

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.

MIC833 4 January 2000

MIC833 Micrel

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.”

Programming the Thresholds

The low-voltage threshold is calculated using:

R1 R2 R3

++

VV

=

IN(lo) REF






R2 R3

+

The high-voltage threshold is calculated using:

R1 R2 R3

++

VV

=

IN(hi) REF






R3

where, for both equations:

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 + R3 = R
A value such as 1MΩ for R
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 accu­racy. The maximum recommended total resistance from V
to ground is 3MΩ.

V

V

IN

DD

R1

R2

R3

604k
1%

56k
1%

340k
1%

5
3
1

MIC833

LTH
HTH











is a reasonable value

TOTAL

470k

OUTVDD

GND

4

2

V

OUT

TOTAL

drain to 3.1V. Using 3.1V for the V

threshold allows

IN(lo)

calculation of the two remaining resistor values.

1M

Ω

V 3.1V 1.24

==

IN(lo)






R2 344k

+






R2 56k=Ω

1M R2 R3 R1Ω− −

()

=

R1 600k=Ω

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
supply voltage. This applys 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.”

Input Transients

The MIC833 is inherently immune to very short negative­going “glitches.” Very brief transients may exceed the V
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 MIC833.
The graph represents the typical allowable transient duration
for a given amount of threshold overdrive that will not toggle
the output.

Input Transient

140

IN

120
100

80
60
40
20

0

MAX. TRANSIENT DURATION (µs)

1 10 100 1000

RESET COMP. OVERDRIVE, V

Response

REF–VLTH

(mV)

Figure 2. Input Transient Response

IN(lo)

Initialization Behavior

Figure 1. Example Circuit

Once the desired trip points are determined, set the V

IN(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:

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
the output of the part will be

between

high

because input HTH will have

the two thresholds,

been higher than the 1.24V reference during initialization.
It is not very likely the part would be powered up in this state;

1M

Ω



V 3.6V 1.24

==

IN(hi)











R3

R3 344k=Ω

Once R3 is determined, the equation for V

can be used

IN(lo)

to determine R2. A single lithium-ion cell, for example, should
not be discharged below 2.5V. Many applications limit the

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.

January 2000 5 MIC833

MIC833 Micrel

Example Application

The battery charger of Figure 3 uses the MIC833 to detect a
low-battery voltage condition (V
current source (I

). Charging current is enabled until a

CHG

charged-battery voltage condition (V

) and enables a constant-

DIS

) is detected; at

CHG

which time the charging-current source is disabled.
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

Constant-Current

Source

OUT

IN

GND

EN

Note 1

D1

Battery

V

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 (V

) if this voltage is never

BAT

lower than 1.5V, the minimum operating VDD of the part.
Voltage thresholds, V

DIS

and V

, are programmed as

CHG

described in the appropriate above paragraph.

Note 2

MIC833

VDD

OUT

V

DIS

R2

CHG

R3

HTH

GND

100k

0.1µFLTH

R4

V

BATT

(to load)

Note 1. D1 may not be required.

It is shown here to
indicate the disabled
current source should
not load the battery.

Figure 3. Battery Charger

Note 2. V

of the MIC833 is

DD

limited to 5.5V maximum.
The part can be powered
by V

BAT

never discharged below
V

DD(min)

if the battery is
= 1.5V

MIC833 6 January 2000

MIC833 Micrel

Package Information

1.90 (0.075) REF

0.95 (0.037) REF

3.02 (0.119)

2.80 (0.110)

0.50 (0.020)

0.35 (0.014)

1.75 (0.069)

1.50 (0.059)

1.30 (0.051)

0.90 (0.035)

0.15 (0.006)

0.00 (0.000)

5-Pin SOT (M)

3.00 (0.118)

2.60 (0.102)

10°

0°

DIMENSIONS:

MM (INCH)

0.20 (0.008)

0.09 (0.004)

0.60 (0.024)

0.10 (0.004)

January 2000 7 MIC833

MIC833 Micrel

MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL + 1 [phone] FAX + 1 [phone] WEB 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.

© 2000 Micrel Incorporated

MIC833 8 January 2000