MIC2775-44YM5TR - Micrel, Inc.

June 2009 1 MIC2775

MIC2775 Micrel, Inc.

MIC2775

Micro-Power Voltage Supervisor

General Description

The MIC2775 is a power supply supervisor that provides

under-voltage monitoring, manual reset capability, and

power-on reset generation in a compact 5-pin SOT package.

Features include an under-voltage detector, a delay genera-

tor, a manual reset input, and both active-high and active-low

reset outputs. The under-voltage detector compares VDD

against a xed threshold. Ten factory-programmed thresholds

are available.

The reset outputs are asserted for no less than 140ms at

power-on and any time the input voltage drops below the

reference voltage. It remains asserted for the timeout period

after the input voltage subsequently rises back above the

threshold boundary. A reset can be generated at any time

by asserting the manual reset input, /MR. This reset output

will remain active at least 140ms after the release of /MR.

The /MR input can also be used to daisy-chain the MIC2775

onto existing power monitoring circuitry or other supervisors.

Hysteresis is included to prevent chattering due to noise.

Typical supply current is a low 3.5µA.

Typical Application

RST

/RST

VDD

/MR

GND

MIC2775-17

VDD

OTHER

LOGIC

/RESET

GND

MICROPROCESSOR

Manual

Reset

1.8V

Features

• Monitors power supply for under-voltage conditions

• Choice of factory-programmed thresholds

• Generates 140ms (minimum) power-on RESET pulse

• Manual reset capability

• Both active-high and active-low RESET outputs

• /RST output valid down to 1.2V

• Ultra-low supply current, 3.5µA typical

• Rejects brief input transients

• No external components

• Pin compatible upgrade for MAX825

• IttyBitty™ 5-pin SOT-23 package

Applications

• Monitoring processor core and input/output voltages

• Computer systems

• PDAs, hand-held PCs

• Embedded controllers

• Telecommunications systems

• Power supplies

Micrel, Inc. • 2180Fortune 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 Junction Temp. Range Package

Standard Marking Pb-Free Marking

MIC2775-XXBM5 UJXX MIC2775-XXYM5 UJXX –40ºC to +85ºC SOT-23-5

MIC2775 Micrel, Inc.

MIC2775 2 June 2009

Pin Conguration

/RST

VDD/MR

RST

GND

SOT-23-5 (M5)

Standard Voltage Options*

Voltage Typical Nominal Threshold

Code Application (VDD) Voltage (VTH)

46 5.0V ±5% 4.68

44 5.0V ±10% 4.43

31 3.3V ±5% 3.09

29 3.3V ±10% 2.93

28 3.0V ±5% 2.81

26 2.85V ±5% 2.67

25 2.70V ±5% 2.53

23 2.5V ±5% 2.34

22 2.4V ±5% 2.25

17 1.8V ±5% 1.69

*There are ten standard versions available with an order increment of 3000 pieces. Samples of standard versions are

normally available from stock. Contact factory for information on non-standard versions. Available in tape-and-reel only.

Pin Description

Pin Number Pin Name Pin Function

1 /RST Digital (Output): Asserted low whenever VDD falls below the reference volt-

age. It will remain asserted for no less than 140ms after VDD returns above

the threshold limit.

2 GND Ground

3 RST Digital (Output): Asserted high whenever VDD falls below the reference volt-

age. It will remain asserted for no less than 140ms after VDD returns above

the threshold limit.

4 /MR Digital (Input): Driving this pin low initiates an immediate and unconditional

reset. Assuming VDD is above the threshold when /MR is released (returns

high), the reset output will be de-asserted no less than 140ms later. /MR

may be driven by a logic signal or a mechanical switch. /MR has an internal

pull-up to VDD and may be left open if unused.

5 VDD Analog (Input): Power supply input and the voltage being monitored.

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MIC2775 Micrel, Inc.

Absolute Maximum Ratings (Note 1)

Supply Voltage (VDD) .......................................–0.3V to +7V

Input Voltage (V/MR) ........................................–0.3V to +7V

RST, (/RST) Current ................................................... 20mA

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

ESD Rating, Note 3 .................................................... 1.5kV

Operating Ratings (Note 2)

Supply Voltage (VDD) .................................. +1.5V to +5.5V

Input Voltage (V/MR) .....................................–0.3V to +6.0V

Ambient Temperature Range (TA) .............. –40°C to +85°C

Package Thermal Resistance (θJA) ....................... 256°C/W

Electrical Characteristics

Note 5; TA = +25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted

Symbol Parameter Condition Min Typ Max Units

IDD Supply Current VDD = VTH +1.6%, /MR, RST, /RST 3.5 µA

open, Note 5

VDD VOLTAGE THRESHOLD

Under-Voltage Threshold On VDD

VTH–1.5%

VTH+1.5%

VHYST Hysteresis Voltage 1 %

RST, /RST OUTPUTS

tPROP Propagation Delay VDD = VTH + 1.5% + 100mV to 20 µs

DD = VTH – 1.5% - 100 mV

tRST Reset Pulse Width 140 280 ms

VOL RST or /RST Output Voltage Low ISINK = 1.6mA; 0.3 V

DD ≥ 1.6V

SINK = 100µA; 0.3 V

DD ≥ 1.2V; Note 4

VOH RST or /RST Output Voltage High ISOURCE = 500µA; 0.8VDD V

DD ≥ 1.5V

SOURCE = 10µA; 0.8VDD V

DD ≥ 1.2V; Note 4

/MR INPUT

VIH Input High Voltage 0.7VDD V

VIL Input Low Voltage 0.3VDD V

tPROP Propagation Delay From V/MR < (VIL –100mV) 5 µs

tMIN Minimum Input Pulse Width Reset Occurs, V/MR < VIL 33 ns

IPU Internal Pull-up Current 100 nA

IIN Input Current, /MR V/MR < VIL 100 nA

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

DD operating range is 1.5V to 5.5V. Output is guaranteed to be asserted down to VDD = 1.2V.

Note 5. V

DD equals nominal “ Typical Application (VDD)” as shown in “Standard Voltage Options Table.”

MIC2775 Micrel, Inc.

MIC2775 4 June 2009

Timing Diagram

V/MR

VIH

VIL

VTH

VDD

V/RST

(ACTIVE LOW)

VOH

VOL

VRST

(ACTIVE HIGH)

VOH

VOL

tRST tRST

> tMIN

tRST

VHYST

Propagation delays not shown for clarity.

Note A. The MIC2775 ignores very brief transients.

See “Applications Information” for details.

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MIC2775 Micrel, Inc.

Functional Diagram

GND

VDD

/MR MIC2775

VREF

RST

/RST

Delay

Line

One Shot

VDD

IPU

Functional Description

VDD Input

The VDD pin is both the power supply terminal and a monitored

input voltage. The voltage at this pin is continually compared

against the internal reference. The trip-point at which a reset

occurs is factory programmed. A reset is triggered if and

when VDD falls below the trip-point. Hysteresis is employed

to prevent chattering due to noise. The comparator on the

VDD input is relatively immune to very brief negative-going

transients.

RST, /RST Reset Outputs

Typically, the MIC2775 is used to monitor the power supply

of intelligent circuits such as microcontrollers and micropro-

cessors. By connecting the appropriate reset output of a

MIC2775 to the reset input of a µC or µP, the processor will

be properly reset at power-on and during power-down and

brown-out conditions. In addition, asserting /MR, the manual

reset input, will activate the reset function.

The reset outputs are asserted any time /MR is asserted or

if VDD drops below the threshold voltage. The reset outputs

remain asserted for tRST(min) after VDD subsequently returns

above the threshold boundary and/or /MR is released. A reset

pulse is also generated at power-on. Hysteresis is included

in the comparator to prevent chattering of the outputs due

to noise.

/MR, Manual Reset Input

The ability to initiate a reset via external logic or a manual

switch is provided in addition to the MIC2775’s automatic su-

pervisory functions. Driving the /MR input to a logic low causes

an immediate and unconditional reset to occur. Assuming

VDD is within tolerance when /MR is released (returns high),

the reset outputs will be de-asserted no less than tRST later.

/MR may be driven by a logic signal or mechanical switch.

Typically, a momentary push-button switch is connected

such that /MR is shorted to ground when the switch contacts

close. The switch may be connected directly between /MR

and GND. /MR has an internal 100nA pull-up current to VDD

and may be left open if unused.

MIC2775 Micrel, Inc.

MIC2775 6 June 2009

Application Information

Ensuring Proper Operation at Low Supply

At levels of VDD below 1.2V, the MIC2775’s /RST output can-

not turn on sufciently to produce a valid logic-low on /RST.

In this situation, circuits driven by /RST could be allowed to

oat, causing undesired operation. (In most cases, however,

it is expected that the circuits driven by the MIC2775 will be

similarly inoperative at VDD ≤ 1.2V.)

If a given application requires that /RST be valid below VDD

= 1.2V, this can be accomplished by adding a pull-down re-

sistor to the /RST output. A value of 100kΩ is recommended

as this is usually an acceptable compromise of quiescent

current and pull-down current. The resistor’s value is not

critical, however. See Figure 1.

/RST

RST

VDD

/MR

Manual

Reset

GND

MIC2775-XX

/RESET

VCC

GND

VCC MICROPROCESSOR

100k

Figure 1. MIC2775 Valid /Reset Below 1.2V

The statements above also apply to the MIC2775’s RST

output. That is, to ensure valid RST signal levels at VDD <

1.2V, a pull-up resistor (as opposed to a pull-down) should

be added to the RST output. A value of 100kΩ is typical for

this application as well. See Figure 2.

/RST

RST

VDD

/MR GND

MIC2775-XX

/RESET

VCC

GND

VCC

Manual

Reset

MICROPROCESSOR

100k

Figure 2. MIC2775 Valid Reset Below 1.2V

Transient response

The MIC2775 is inherently immune to very short negative-

going “glitches.” Very brief transients may exceed the voltage

threshold without tripping the output.

As shown in Figure 3, in general the narrower the transient,

the deeper the threshold overdrive that will be ignored by

the MIC2775. The graph represents the typical allowable

transient duration for a given amount of threshold overdrive

that will not generate a reset.

100

0 500 1000 1500 2000

RESET COMP. OVERDRIVE, V

REF

–V

(mV)

Typical V

TransientResponse

Figure 3. Typical VDD Transient Response

June 2009 7 MIC2775

MIC2775 Micrel, Inc.

Package Information

SOT-23-5 (M5)

MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA

t e l + 1 (408) 944-0800 f a x + 1 (408) 474-1000 w e b http://www.micrel.com

This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.

Micrel reserves the right to change circuitry and specications at any time without notication to the customer.

Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can

reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into

the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a signicant injury to the user. A Purchaser's

use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify

Micrel for any damages resulting from such use or sale.