MIC2778-2YM5-TR Datasheet MIC2778-1YM5-TR, MIC2778-2YM5-TR, MIC2778-1BM5-TR | P1-P3

January 2005 1 M9999-011405

MIC2778 Micrel

MIC2778

Voltage Monitor with Adjustable Hysteresis

General Description

The MIC2778 is a voltage monitor—uniquely designed to

detect two separate voltage thresholds—combined with a

delay generator and logic. It is designed for monitoring the

battery supply of portable digital systems, particularly PDAs,

pagers, and cellular telephones.

High- and low-voltage thresholds can be adjusted inde-

pendently, allowing for wide hysteresis. Voltage detection

thresholds are accurate to 2%.

If the battery voltage falls below the low-voltage threshold,

the output (RST) is asserted and latched, preventing system

operation until the battery is replaced or recharged. Internal

logic prevents the output from chattering due to battery

recovery or load removal. The output is asserted for 140ms

(minimum) when a fresh battery is inserted. For applications

not requiring built-in delay, see MIC841.

The IC’s power supply input is separate from the detector

inputs, allowing the MIC2778 to be powered from a down-

stream supply, such a boost converter. Supply current is

extremely low (1µA, typical), making it ideal for portable

applications.

A high-precision 1% grade is available. The MIC2778 is sup-

plied in Micrel’s IttyBitty™ 5-lead SOT-23-5 package.

Typical Application

HTH

R STVDD

LTH

GND

MIC2778

604k

56k

340k

E N

OUT

B Y P

GND

MIC5207-3.0BM5

100k

Li-Ion

Cell

470pF

OU T

3.0V

4.7µF

BAT(hi)

= 3.6V

BAT(lo)

= 3.1V

Cellular Telephone Battery Monitor

Features

• Optimized for PDAs, cellular telephones, pagers,

and other battery-powered devices

• Independently adjustable high- and

low-voltage thresholds

• Internal logic prevents battery-voltage-ﬂuctuation chatter

• High ±2% voltage threshold accuracy; 1% available

• Built in 140ms (minimum) delay deglitches output

• Extremely low 1µA typical supply current

• For applications not requiring built-in delay, see MIC841

• Immune to brief power supply transients

• 5-lead SOT-23 package

Applications

• PDAs

• Pagers

• Cordless phones

• Consumer electronics

• Embedded controllers

• Personal electronics

Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

IttyBitty™ is a trademark of Micrel, Inc.

Ordering Information

Part Number Accurary Temperature Range Package

Standard Marking Pb-Free Marking

MIC2778-2BM5 UFB MIC2778-2YM5 UFB* 2% -40°C to +85°C SOT-23-5

MIC2778-1BM5 UFA MIC2778-1YM5 UFA* 1% -40°C to +85°C SOT-23-5

* Underscore indicates a Pb-Free part.

MIC2778 Micrel

M9999-011405 2 January 2005

Pin Description

Pin Number Pin Name Pin Function

1 HTH

High-Voltage Theshold (Input): Analog input to a comparator. When the level

on this pin initially rises above V

REF

, the delay generator cycles and the RST

remains low for a minimum of 140ms.

2 GND Ground

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

voltage monitor input assigned to detect a low voltage condition. When

the level on this pin falls below V

REF

, RST is asserted and the condition is

latched until V

HTH

> V

REF

RST Reset (Output): Active-low, open-drain output. This output is asserted and

latched when V

LTH

REF

, indicating a low voltage condition. This state

remains latched until V

HTH

> V

REF

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

Pin Conﬁguration

HTH

VDDR S

LTH

4 5

GND

SOT-23-5 (M5)

January 2005 3 M9999-011405

MIC2778 Micrel

Absolute Maximum Ratings (Note 1)

Supply Voltage (V

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

Input Voltages (V

, V

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

RST Output Current (I

RST

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

Storage Temperature (T

) ........................ –65°C to +150°C

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

Operating Ratings (Note 2)

Supply Voltage (V

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

Input Voltages (V

RST

, V

LTH

, V

HTH

) ................–0.3V to +6.0V

Ambient Temperature Range (T

) .............. –40°C to +85°C

Package Thermal Resistance ................................

256°C/W

Electrical Characteristics

1.5V ≤ V

≤ 5.5V; T

= +25°C, bold values indicate –40°C ≤ T

≤ +85°C; unless noted

Symbol Parameter Condition Min Typ Max Units

Supply Current RST not asserted 1 2

µA

LTH,

HTH

Input Leakage Current 5 pA

REF

Reference Voltage 1.240 V

MIC2778-2

1.215 1.265 V

MIC2778-1

1.228 1.252 V

Propagation Delay V

LTH

= V

REF(max)

+100mV to 5 µs

REF(min)

– 100mV

RESET

Reset Pulse Width 140 420 ms

RST

Voltage-Low Reset RST asserted, I

SINK

= 1.6mA, V

≥ 1.6V 0.3 V

RST asserted, I

SINK

= 100µA, V

≥ 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. V

operating range is 1.5V to 5.5V. Output is guaranteed to be held low down to V

= 1.2V.

Timing Diagram

HTH

BATT

LTH

RSTH

RSTL

RST

Propagation delays not shown for clarity.

Note A. The MIC2778 ignores very brief transients.

See “Applications Information” for details.

P1-P3 P4-P6

MIC2778-2YM5-TR

Mfr. #:

Buy MIC2778-2YM5-TR

Manufacturer:

Microchip Technology / Micrel

Description:

Supervisory Circuits V-Supervisor w/Adj. Hysteresis, Open-Drain Ouput, 2% Accuracy

Lifecycle:

New from this manufacturer.

Delivery:

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MIC2778-2YM5-TR

MIC2778-2YM5-TR

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