MAX824ZEXK [MICREL]

Voltage Supervisor with Watchdog Timer and Manual Reset;


型号：	MAX824ZEXK
厂家：	MICREL SEMICONDUCTOR
描述：	Voltage Supervisor with Watchdog Timer and Manual Reset
文件：	总14页 (文件大小：957K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

MAX823/4/5

Voltage Supervisor with Watchdog Timer

and Manual Reset

Revision 1.0

Features

General Description

 Precision 1.665V to 4.625V power supply monitor

 ±0.5% threshold accuracy at TA = +25°C

 ±1.5% threshold accuracy from TA = –40°C to +125°C

 3.8µA supply current (S,R,T,W,Y,Z options)

 4.8µA supply current (L,M options)

 Manual reset input (MAX823/5)

 140ms (min.) reset timeout period

 1.6s (typ.) watchdog timeout period

The MAX823/4/5 voltage supervisory circuits combine

low-current, manual reset input, watchdog timer, active-

high and active-low push-pull outputs. The reset outputs

are asserted and held when the supply voltage falls below

the factory-programmed threshold voltage, when the /MR

pin is pulled low, or if the watchdog times out. Reset is

asserted for the reset timeout delay after the supply

voltage increases above the rising threshold voltage or

when manual reset input is asserted high.

 Active-high and active-low push-pull outputs

 Guaranteed reset output valid to VCC = 1V

 40°C to +125°C junction temperature range

 5-pin SOT23 & SC70 packages

The MAX823/4/5 features an integrated pull-up resistor on

the /MR pin. An active-low push-pull reset output (/RESET)

and an active-high reset output (RESET) provide flexibility

when interfacing with various microcontrollers, PMICs, or

load switches. The watchdog input can be left

unconnected for applications that do not require watchdog

monitoring.

 8x lower watchdog input current than competition

Applications

The MAX823/4/5 consumes a quiescent current of only

3.8µA and is offered in standard SOT23-5 and SC70-5

packages. It is rated for the –40°C to +125°C temperature

range.

 Computers and Controllers

 Embedded Controllers

 Intelligent Instruments

 Automotive Systems

Datasheets and support documentation are available on

Micrel’s web site at: www.micrel.com.

 Critical µP Monitoring

 Portable/ Battery-Powered Equipment

Typical Application

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

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

FUNCTION

MAX823

MAX824

MAX825

Active-Low Reset



Active-High Reset

Watchdog Input

−



−



−



Manual Reset Input



Ordering Information⁽¹⁾

V_RST: Nominal Threshold

Voltage (V)

Part Number

Top Marking

X3L

Package

MAX823LEUK

MAX823MEUK

MAX823REUK

MAX823SEUK

MAX823TEUK

MAX823WEUK

MAX823YEUK

MAX823ZEUK

MAX823LEXK

MAX823MEXK

MAX823REXK

MAX823SEXK

MAX823TEXK

MAX823WEXK

MAX823YEXK

MAX823ZEXK

4.625

4.375

2.625

2.925

3.075

1.665

2.188

2.315

4.625

4.375

2.625

2.925

3.075

1.665

2.188

2.315

SOT23-5

SC70-5

X3M

X3R

X3S

X3T

X3W

X3Y

X3Z

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Ordering Information (Continued)⁽¹⁾

V_RST: Nominal Threshold

Voltage (V)

Part Number

Top Marking

Package

MAX824LEUK

MAX824MEUK

MAX824REUK

MAX824SEUK

MAX824TEUK

MAX824WEUK

MAX824YEUK

MAX824ZEUK

MAX824LEXK

MAX824MEXK

MAX824REXK

MAX824SEXK

MAX824TEXK

MAX824WEXK

MAX824YEXK

MAX824ZEXK

X4L

X4M

X4R

X4S

X4T

X4W

X4Y

X4Z

4.625

4.375

2.625

2.925

3.075

1.665

2.188

2.315

4.625

4.375

2.625

2.925

3.075

1.665

2.188

2.315

SOT23-5

SC70-5

V_RST: Nominal Threshold

Voltage (V)

Part Number

Top Marking

Package

MAX825LEUK

MAX825MEUK

MAX825REUK

MAX825SEUK

MAX825TEUK

MAX825WEUK

MAX825YEUK

MAX825ZEUK

MAX825LEXK

MAX825MEXK

MAX825REXK

MAX825SEXK

MAX825TEXK

MAX825WEXK

MAX825YEXK

MAX825ZEXK

Note:

X5L

X5M

X5R

X5S

X5T

X5W

X5Y

X5Z

4.625

4.375

2.625

2.925

3.075

1.665

2.188

2.315

4.625

4.375

2.625

2.925

3.075

1.665

2.188

2.315

SOT23-5

SC70-5

1. All devices are available in tape-and-reel only. Contact Micrel for tape-and-reel options.

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Pin Configuration

MAX823

MAX824

SOT23(EUK) &SC70(EXK)

Top View

MAX825

SOT23(EUK) &SC70(EXK)

Top View

SOT23(EUK) &SC70(EXK)

Top View

Pin Description

Pin Number

MAX823

Pin Number

MAX824

Pin Number

MAX825

Pin Name Pin Function

Active-Low Reset Output. Pulses low for 200ms when triggered, and

remains low whenever V_CCis below the reset threshold or when /MR is

a logic low. It remains low for 200ms after one of the following occurs:

V_CCrises above the reset threshold, the watchdog triggers a reset, or

/MR goes low to high.

/RESET

GND

Ground.

Active-High Reset Output. Pulses high for 200ms when triggered, and

remains high whenever V_CCis below the reset threshold or when /MR

is a logic low. It remains high for 200ms after one of the following

occurs: V_CCrises above the reset threshold, the watchdog triggers a

reset, or /MR goes low to high. RESET is the inverse of /RESET.

RESET

Watchdog Input. If WDI remains either high or low for longer than the

watchdog timeout period, the internal watchdog timer runs out and a

reset is triggered. The internal watchdog timer clears whenever reset

is asserted, or whenever WDI sees a rising or falling edge. If WDI is

left unconnected or is connected to a three-stated buffer output, the

watchdog feature is disabled.

WDI

/MR

Manual Reset Input. A logic low on /MR asserts reset. Reset remains

asserted as long as /MR is held low and for 200ms after /MR returns

high. The active-low input has an internal 52kΩ pull-up resistor. It can

be driven from a CMOS logic line or shorted to ground with a switch.

Leave open or connect to VCC if unused.

Supply Voltage Pin. VCC is the input to the supply voltage monitor.

When the supply voltage falls below the reset threshold voltage, reset

outputs (/RESET and RESET) are triggered immediately. When the

supply voltage rises above the reset threshold plus hysteresis voltage,

the reset outputs remain asserted for the duration of the reset timeout

period. An optional 0.1µF bypass capacitor mounted close to VCC

provides additional transient immunity.

VCC

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Absolute Maximum Ratings⁽²⁾

Operating Ratings⁽³⁾

Supply Voltage (V_CC).................................... +1.0V to +5.5V

Watchdog Input (WDI)...........................................0V to V_CC

Junction Temperature (T_J) ........................–40°C to +125°C

Junction Thermal Resistance

Supply Voltage (V_CC).................................... 0.3V to 6.0V

/MR, WDI, RESET, /RESET.................. 0.3V to V_CC+0.3V

Input Current (All Pins except RESET, /RESET)........20mA

Output Current (RESET, /RESET)..............................20mA

Junction Temperature (T_J) ........................40°C to +150°C

Storage Temperature (Ts).........................65°C to +150°C

ESD Rating⁽⁴⁾(Human Body Model)(MAX823/4/5) ........3kV

5-Pin SOT23....................................................215°C/W

5-Pin SC70 ......................................................250°C/W

Electrical Characteristics⁽⁵⁾

V_CC= 4.7V to 5.5V for MAX823/4/5L, V_CC= 4.5V to 5.5V for MAX823/4/5M, V_CC= 3.15V to 3.6V for MAX823/4/5T, V_CC= 3.0V to 3.6V

for MAX823/4/5S, V_CC= 2.7V to 3.6V for MAX823/4/5R, V_CC= 2.38V to 2.75V for MAX823/4/5Z, V_CC= 2.25V to 2.75V for

MAX823/4/5Y, V_CC= 1.75V to 2.0V for MAX823/4/5W; T_J= +25˚C, bold values⁽⁶⁾indicate –40˚C ≤ T_J≤ +125˚C, unless otherwise noted.

Parameter

Condition

Min.

Typ.

Max.

Units

Power Suppy Input

1.0

5.5

Supply Voltage (V_CC

)

L/M (WDI and /MR unconnected)

4.8

3.8

µA

Supply Current (I_VCC

)

8.4

T/S/R/Z/Y/W (WDI and /MR unconnected)

Reset Threshold Voltage

4.602

4.556

4.353

4.309

3.060

3.029

2.910

2.881

2.612

2.586

2.303

2.280

2.177

2.155

1.657

1.640

4.625

4.375

3.075

2.925

2.625

2.315

2.188

1.665

4.648

4.694

4.397

4.441

3.090

3.121

2.940

2.969

2.638

2.664

2.327

2.350

2.199

2.221

1.673

1.690

L (falling) T_A= 25C

L (falling) 40C  T_A +125C

M (falling) T_A= 25C

M (falling) –40C  T_A +125C

T (falling) T_A= 25C

T (falling) –40C  T_A +125C

S (falling) T_A= 25C

S (falling) –40C  T_A +125C

R (falling) T_A= 25C

Reset Threshold Voltage

(V_RST

)

R (falling) –40C  T_A +125C

Z (falling) T_A= 25C

Z (falling) –40C  T_A +125C

Y (falling) T_A= 25C

Y (falling) –40C  T_A +125C

W (falling) T_A= 25C

W (falling) –40C  T_A +125C

L, M

ppm/˚C

Reset Threshold

Hysteresis

T, S, R, Z, Y, W

Reset Threshold Tempco

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Electrical Characteristics (Continued)⁽⁵⁾

V_CC= 4.7V to 5.5V for MAX823/4/5L, V_CC= 4.5V to 5.5V for MAX823/4/5M, V_CC= 3.15V to 3.6V for MAX823/4/5T, V_CC= 3.0V to 3.6V

for MAX823/4/5S, V_CC= 2.7V to 3.6V for MAX823/4/5R, V_CC= 2.38V to 2.75V for MAX823/4/5Z, V_CC= 2.25V to 2.75V for

MAX823/4/5Y, V_CC= 1.75V to 2.0V for MAX823/4/5W; T_J= +25˚C, bold values⁽⁶⁾indicate –40˚C ≤ T_J≤ +125˚C, unless otherwise noted.

Parameter

Condition

Min.

140

Typ.

Max.

280

Units

Reset Timeout Period

200

(t_RP

)

Reset Time

VCC to /RESET Delay

µs

(t_RD

Reset Outputs (/RESET, RESET)

L, M: V_CCV_{RST (MAX)}, I_SOURCE= 120µA

)

V_CC– 1.5

0.8 × V_CC

/RESET Output Voltage

High (V_OH

T, S, R, Z, Y: V_CCV_{RST (MAX)}

)

I_SOURCE= 30µA

W: V_CCV_{RST (MAX)}, I_SOURCE= 20µA

L, M: V_CCV_{RST (MIN)}, I_SINK= 3.2mA

0.4

0.3

T, S, R, Z, Y, W: V_CCV_{RST (MIN)}

I_SINK= 1.2mA

/RESET Output Voltage

Low (V_OL

)

0.3

T_A= 0˚C to +70˚C, V_CC= 1V, I_SINK=50µA

V_CC= 1.2V, I_SINK=100µA

800

L, M: /RESET = 0V, V_CC= 5.5V

µA

/RESET Output Short-

Circuit Current⁽⁷⁾

T, S, R, Z, Y, W: /RESET = 0V,

V_CC= 3.6V

400

µA

RESET Output Voltage

0.8 × V_CC

V_CC1.6VI_SOURCE= 150µA

High (V_OH

)

0.4

0.3

L, M: V_CCV_{RST (MAX)}, I_SINK= 3.2mA

RESET Output Voltage

Low (V_OL

T, S, R, Z, Y, W: V_CCV_{RST (MAX)}

I_SINK= 1.2mA

)

Watchdog Input (WDI)⁽⁸⁾

Watchdog Timeout

1.12

2.40

1.60

Period (t_WD

)

Watchdog Pulse Width

0.3 ×

V_CC

Watchdog Input Low

Voltage (V_IL)

Watchdog Input High

Voltage (V_IH)

0.7 × V_CC

-20

WDI = V_CC

WDI = 0V

µA

Watchdog Input Current

-15

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Electrical Characteristics (Continued)⁽⁵⁾

V_CC= 4.7V to 5.5V for MAX823/4/5L, V_CC= 4.5V to 5.5V for MAX823/4/5M, V_CC= 3.15V to 3.6V for MAX823/4/5T, V_CC= 3.0V to 3.6V

for MAX823/4/5S, V_CC= 2.7V to 3.6V for MAX823/4/5R, V_CC= 2.38V to 2.75V for MAX823/4/5Z, V_CC= 2.25V to 2.75V for

MAX823/4/5Y, V_CC= 1.75V to 2.0V for MAX823/4/5W; T_J= +25˚C, bold values⁽⁶⁾indicate –40˚C ≤ T_J≤ +125˚C, unless otherwise noted.

Parameter

Condition

Min.

Typ.

Max.

Units

Manual Reset Input (/MR)

Input Low Voltage (V_IL)

Input High Voltage (V_IH)

/MR Pulse Width

0.3 × V_CC

0.7 × V_CC

1.0

µs

/MR Noise Immunity (pulse

width with no reset)

100

/MR to RESET Delay

/MR Internal Pull-Up Resistor

Notes:

500

kΩ

2. Exceeding the absolute maximum ratings may damage the device.

3. The device is not guaranteed to function outside its operating ratings.

4. Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF.

5. Specification for packaged product only.

6. Overtemperature limits are guaranteed by design and not product tested.

7. The /RESET short-circuit current is the maximum pull-up current when /RESET is driven low by µP bidirectional reset pin.

8. The WDI input is designed to drive a three-state output device with a 10µA maximum leakage current and a maximum capacitance of 200pF.

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Typical Characteristics

Supply Current

vs. Input Voltage

Supply Current

vs. Temperature

RESET Timeout Period

vs. Temperature

250

200

150

100

MAX824L, V_CC= 5.5V

MAX823W

MAX823W, V_CC= 2V

MAX824L

MAX825S, V_CC= 3.25V

MAX825S

/MR = OPEN

WDI = OPEN

/MR = Open

WDI = Open

/MR = OPEN

WDI = OPEN

0.5

1.5

2.5

3.5

4.5

5.5

-40

-20

100 120

-40 -20

80 100 120

INPUT VOLTAGE (V)

TEMPERATURE (ꢀC)

TEMPERATURE (°C)

Normalized Reset Threshold

vs. Temperature

/MR to RESET Delay

vs. Temperature

Watchdog Timeout Period vs.

Temperature

800

700

600

500

400

300

200

100

1.06

1.8

1.6

1.4

1.2

1.04

1.02

0.98

0.96

0.94

0.92

0.8

0.6

0.4

0.2

-40 -20

20 40 60 80 100 120 140

-40 -20

80 100 120

-40 -20

80 100 120

TEMPERATURE (°C)

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Functional Diagram

Timing Diagram

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Functional Description

Design and Product Advantages

The MAX823/4/5 is series of a voltage supervisor reset

IC with a manual reset input, watchdog input, and dual

reset outputs. The MAX823/4/5 asserts and holds a reset

when the supply voltage falls below the factory-

programmed threshold voltage, when /MR is at low logic

level, or when watchdog input times out. Reset is

asserted for a fixed reset timeout period after the supply

voltage increases above the rising threshold voltage or

when the manual reset input is asserted high.

The MAX823/4/5 features an active-low, push-pull reset

output (/RESET) and an active-high, push-pull reset

output (RESET). It also contains 52kΩ pull-up resistors

on the /MR input to make it easy to connect to

pushbutton inputs. The MAX823/4 also features a

watchdog input (WDI).

Figure 1. Manual Reset Function

When Functioning as a Voltage Supervisor

The /RESET pin is asserted whenever V_CCfalls below the

reset threshold voltage, V_RST(V_CC< V_RST). The VCC pin

circuitry includes hysteresis to prevent /RESET or

RESET pin chattering due to noise. The /RESET pin

remains asserted for the duration of the reset timeout

delay (t_RP) after V_CChas risen above the reset threshold

voltage plus the hysteresis. The reset function ensures

that a microprocessor is properly reset and powers up in

a known condition after a power failure. The /RESET

remains valid with V_CCas low as 1V. The RESET output

is a complement of the /RESET output.

Manual Reset Input (/MR)

The /MR input pin has integrated pull-up resistors to keep

the current consumption low when the pushbutton switch

is pressed.

Reset Outputs (/RESET and RESET)

There are two reset outputs: /RESET and RESET. Both

outputs are push-pull, which eliminates the need for pull-

up resistors. The RESET output is the inverse of the

/RESET output.

Asserting /RESET and RESET Outputs

When Functioning as a Manual Reset

The reset outputs /RESET and RESET are asserted

while the /MR pin is driven low. Both reset outputs remain

asserted for a factory-programmed reset timeout delay

time, t_RP. The typical value of a reset timeout period is

200ms. The /RESET pin is driven low while the RESET

pin is driven high whenever /MR is pulled low.

Figure 2. Voltage Supervisor Function

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

V_CCTransient

Watchdog Input

The MAX823/4/5 is relatively immune to small negative-

going V_CCglitches below the reset threshold. As shown in

Figure 4, the overdrive voltage is the difference between

the threshold voltage and the minimum point of the V_CC

glitch. Typically, an overdrive of 100mV with duration of

2μs or less will not cause a reset.

The MAX823/4 has an on-chip watchdog timer that can

reset the microprocessor if it fails to strobe the WDI input

within a preset timeout period (t_WD). If the WDI pin is left

unconnected, this function is disabled. The watchdog

timeout period starts when the reset outputs are

deasserted or either

high-to-low or low-to-high

transition occurs before the watchdog timeout period

(t_WD). If the watchdog timer times out, then the reset

outputs will assert and stay asserted for a reset timeout

period (t_RP). The watchdog timer is also cleared whenever

the reset outputs are asserted by /MR, or if V_CCfalls

below V_RST. The watchdog timer starts again whenever

the reset outputs are de-asserted.

Figure 4. VCC Transient

Reset Valid up to V_CC= 1V

The MAX823/4/5 is a supervisory circuit that monitors the

power supply voltage level. If the power supply voltage

level falls below the factory-programmed threshold level,

then the reset signals are asserted. The MAX823/4/5

maintains the reset states with V_CCas low as 1V.

Supply Bypass Capacitor

An optional 0.1µF input bypass capacitor can be placed

from VCC (Pin 6) to GND (Pin 2) to increase glitch

rejection and provides additional transient immunity.

Figure 3. Watchdog Input

Watchdog Input Current

The WDI input current is the current sourced or sinked by

the WDI pin when the WDI input is driven low or high,

respectively. The WDI input is designed to drive a tri-

state output device with a 10µA maximum leakage

current and a maximum capacitance of 200pF.

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Typical Applications

Figure 5. MAX825 for Precision Power Good Function

Figure 6. MAX823 Used for Load Switch

Figure 7. MAX824 Used for Microcontroller Reset with Watchdog Input

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Package Information⁽⁹⁾

5-Pin SOT23 (EUK)

Revision 1.0

January 14, 2014

Micrel, Inc.

MAX823/4/5

Package Information (Continued)⁽⁹⁾

5-Pin SC70 (EXK)

Note:

9. Package information is correct as of the publication date. For updates and the most current information, go to www.micrel.com.

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

TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com

Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This

information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,

specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual

property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability

whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties

relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.

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 significant 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.

Revision 1.0

January 14, 2014

MAX824ZEXK [MICREL]

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