Datasheet ADM8616 Datasheet (Analog Devices)

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Low-Voltage Watchdog

Preliminary Technical Data

FEATURES

Precision 1.8V to 5V Power Supply Monitoring 9 Reset Threshold Options:

1.58V to 4.63V 4 Reset Timeout Options:

1ms, 20ms, 140ms, 1120ms Watchdog Timer Reset Output Stages

Push-Pull Active-Low (ADM8616)

Open-Drain Active-Low (ADM8617) Low Power Consumption (3µA) Guaranteed Reset Output valid to V Power Supply Glitch Immunity Specified Over -40°C to +85°C Temperature Range 4-Lead SC70 Package

APPLICATIONS

Microprocessor Systems Computers Controllers Intelligent Instruments Portable Equipment

GENERAL DESCRIPTION

The ADM8616/ADM8617 are supervisory circuits which monitor power supply voltage levels and code execution integrity in microprocessor-based systems. A power-on-reset signal is generated when the supply voltage rises to a preset threshold level.The ADM8616/ADM8617 have an on-chip watchdog timer which can reset the microprocessor if it fails to strobe within a preset timeout period.

=1V

Supervisory Circuits in 4-Lead SC70

ADM8616/ADM8617

FUNCTIONAL BLOCK DIAGRAMS

ADM8616

REF

GND

RESET

GENERATOR

WATCHDOG

DETECTOR

WDI

Figure 1.

Each part is available in a choice of the following 9 reset threshold options: 1.58V, 1.67V, 2.19V, 2.32V, 2.63V, 2.93V,

3.08V, 4.38V and 4.63V. There are four reset timeout options1ms, 20ms, 140ms and 1120ms. There are also four possible watchdog timeouts available- 6.3ms, 102ms, 1.6s and 25s. The parts differ in terms of reset output configuration, ADM8616 is active low with a Push- Pull output while ADM8617 is active low with an Open- Drain Output.

4-5-6

Rev. PrE

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.

The ADM8616/ADM8617 are available in 4-lead SC70 packages and typically consume only 3µA, making them suitable for use in low power portable applications.

ADM8616/ADM8617 Preliminary Technical Data

ADM8616/ADM8617—SPECIFICATIONS

Table 2. VCC=Full Operating Range, TA=-40oC to 85oC, unless otherwise noted

Parameter Min Typ Max Units Test Conditions/Comments

SUPPLY VCC Operating Voltage Range 1 5.5 V

Supply Current 10 20 µA VCC=5.5V 5 12 µA VCC=3.6V

RESET THRESHOLD VOLTAGE

ADM861_L ADM861_M ADM861_T ADM861_S ADM861_R ADM861_Z ADM861_Y ADM861_W

ADM861_V RESET THRESHOLD TEMPERATURE COEFFICIENT 40 ppm/°C RESET THRESHOLD HYSTERESIS 3 mV RESET TIMEOUT PERIOD ADM861_ _A 1 1.4 2 ms ADM861_ _B 20 28 40 ms ADM861_ _C 140 200 280 ms ADM861_ _D 1120 1600 2240 ms VCC TO RESET DELAY 40 µs V PUSH-PULL OUTPUT (ADM8616)

RESET

Output Voltage

0.3 V VCC>=1.2V, I

0.3 V VCC>=2.7V, I

0.4 V VCC>=4.5V, I

0.8x VCC V VCC>=2.7V, I

RESET

Rise Time

OPEN-DRAIN OUTPUT (ADM8617)

RESET

Output Voltage

0.3 V VCC>=1.2V, I

0.3 V VCC>=2.7V, I

0.4 V VCC>=4.5V, I

Open-Drain Reset Output Leakage Current 1 µA WATCHDOG INPUT Watchdog Timeout Period

ADM861_ _ _W 4.3 6.3 9.3 ms ADM861_ _ _X 71 102 153 ms ADM861_ _ _Y 1.12 1.6 2.24 s

ADM861_ _ _Z 17.9 25.6 38.4 s WDI Pulse Width 50 ns VIL=0.3xVCC, VIH=0.7xVCC, WDI Input Threshold 0.3xVCC V

0.7xVCC V WDI Input Current 120 160 µA V

4.50 4.63 4.75 V

4.25 4.38 4.50 V

3.00 3.08 3.15 V

2.85 2.93 3.00 V

2.55 2.63 2.70 V

2.25 2.32 2.38 V

2.12 2.19 2.25 V

1.62 1.67 1.71 V

1.52 1.58 1.62 V

falling at 1mV/µs

0.3 V VCC>=1.0V, I

-1.5 V VCC>=4.5V, I

5 25 ns

0.3 V V

From 10% to 90% V

=3.3V

>=1.0V, I

=50µA

SINK

=100µA

SINK

=1.2mA

SINK

=3.2mA

SINK

SOURCE

=50µA

SINK

=100µA

SINK

=1.2mA

SINK

=3.2mA

SINK

=500µA

=800µA

, CL=5pF,

= VCC, time average

WDI

-20 -15 µA V

=0, time average

WDI

Rev. PrE | Page 2 of 10

Preliminary Technical Data ADM8616/ADM8617

ABSOLUTE MAXIMUM RATINGS

Table 3. TA = 25°C unless otherwise noted.

Parameter Rating VCC -0.3V to +6V RESET

/RESET

Output Current (RESET, Operating Temperature Range -40°C to +85°C Storage Temperature Range -65°C to +150°C

θJA Thermal Impedance, SC70

Lead Temperature Soldering (10 sec) 300°C Vapour Phase (60 sec) 215°C Infrared (15 sec) 220°C

RESET

)

-0.3V to +6V 20mA

146°C/W

Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Rev. PrE | Page 3 of 10

ADM8616/ADM8617 Preliminary Technical Data

PIN CONFIGURATIONS AND FUNCTIONAL DESCRIPTIONS

4GND

ADM861x

TOP VIEW

(Not to Scale)

RESET/RESET

WDI

Pin Configuration

Table 4. Pin Functional Descriptions

Pin No. Name Description

1 GND Ground 2

3 WDI

4 VCC Power Supply Voltage being Monitored.

RESET

Active-Low Reset Output, which is asserted whenever V Push-Pull Output Stage for ADM8616. Open-Drain Output Stage for ADM8617. Watchdog Input. Generates a reset if the logic level on the pin remains low or high for the

duration of the watchdog timeout. The timer is cleared if a logic transition occurs on this pin or if a reset is generated. Leave floating to disable the watchdog timer.

is below the reset.threshold, VTH.

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

Rev. PrE | Page 4 of 10

ADM8616/ADM8617 Preliminary Technical Data

Rev. PrE | Page 5 of 10

TYPICAL PERFORMANCE CHARACTERISTICS

Figure 2. Supply Current vs. Temperature

Figure 3. Normalized RESET Timeout Period vs. Temperature

Figure 5. Normalized Watchdog Timeout Period vs. Temperature

Figure 6. Normalised RESET Threshold vs. Temperature

Figure 4. V

to RESET Output Delay vs. Temperature

Figure 7.Maximum V

Transient Duration vs. RESET Threshold Overdrive

ADM8616/ADM8617 Preliminary Technical Data

Figure 8. Voltage Output Low vs. I

SINK

Figure 9. Voltage Output High vs. I

SOURCE

Rev. PrE | Page 6 of 10

Preliminary Technical Data ADM8616/ADM8617

CIRCUIT DESCRIPTION

The ADM8616/ADM8617 provide microprocessor supply voltage supervision by controlling the microprocessor’s reset input. Code-execution errors are avoided during power-up, power-down, and brownout conditions by asserting a reset signal when the supply voltage is below a preset threshold and by allowing supply voltage stabilization with a fixed-timeout reset pulse after the supply voltage rises above the threshold. In addition, problems with microprocessor code execution can be monitored and corrected with a watchdog timer. By including watchdog strobe instructions in microprocessor code, a watchdog timer can detect if the microprocessor code breaks down or becomes stuck in an infinite loop. If this happens, the watchdog timer asserts a reset pulse that restarts the microprocessor in a known state.

RESET OUTPUT

The ADM8616 features an active-low, push-pull reset output while the ADM8617 features an active-low open drain reset output.. The reset signal is guaranteed to be logic low and logic high respectively for V

The reset output is asserted when V threshold (V

) or when WDI is not serviced within the

watchdog timeout period (t duration of the reset active timeout period (t above the reset threshold or after the watchdog timer times out. Figure 10 illustrates the behavior of the reset outputs.

RESET

1V 0V

down to 1V.

is below the reset

). Reset remains asserted for the

Figure 10. Reset Timing Diagram

) after VCC rises

WATCHDOG INPUT

The ADM8616/ADM8617 feature a watchdog timer which monitors microprocessor activity. A timer circuit is cleared with every low-to-high or high-to-low logic transition on the watchdog input pin (WDI), which detects pulses as short as 50 ns. If the timer counts through the preset watchdog timeout period

), reset is asserted. The microprocessor is required to toggle

the WDI pin to avoid being reset. Failure of the microprocessor to toggle WDI within the timeout period therefore indicates a code execution error, and the reset pulse generated restarts the microprocessor in a known state.

In addition to logic transitions on WDI, the watchdog timer is also cleared by a reset assertion due to an undervoltage condition on V cleared and does not begin counting again until reset deassserts. The watchdog timer can be disabled by leaving WDI floating or by three-stating the WDI driver.

RESET

When reset is asserted, the watchdog timer is

CC.

WDI

1V 0V

Figure 11. Watchdog Timing Diagram

04534-0-021

Rev. PrE | Page 7 of 10

ADM8616/ADM8617 Preliminary Technical Data

APPLICATION INFORMATION

WATCHDOG INPUT CURRENT

In order to minimize watchdog input current (and minimize overall power consumption), leave WDI low for the majority of the watchdog timeout period. When driven high, WDI can draw as much as 160 µA. Pulsing WDI low-high-low at a low duty cycle reduces the effect of the large input current. When WDI is unconnected, a window comparator disconnects the watchdog timer from the reset output circuitry so that reset is not asserted when the watchdog timer times out.

NEGATIVE-GOING VCC TRANSIENTS

To avoid unnecessary resets caused by fast power supply transients, the ADM8616/ADM8617 are equipped with glitch rejection circuitry. The typical performance characteristic in Error! Reference source not found. plots V

transient

duration versus the transient magnitude. The curve shows combinations of transient magnitude and duration for which a reset is not generated for 4.63 V and 2.93 V reset threshold parts. For example, with the 2.93 V threshold, a transient that goes 100 mV below the threshold and lasts 8 µs typically does not cause a reset, but if the transient is any bigger in magnitude or duration, a reset is generated. An optional 0.1 µF bypass capacitor mounted close to V

provides additional glitch

rejection.

ENSURING RESET VALID TO VCC = 0 V

The active-low reset output is guaranteed to be valid for VCC as low as 1V. However, by using an external resistor, valid outputs

as low as 0 V are possible. The resistor, connected

for V

between

unable to sink current. A large resistance such as 100 kΩ should be used so that it does not overload the reset output when V above 1 V.

and ground, pulls the output low when it is

RESET

WATCHDOG SOFTWARE CONSIDERATIONS

In implementing the microprocessor’s watchdog strobe code, quickly switching WDI low-high and then high-low (minimizing WDI high time) is desirable for current consumption reasons. However, a more effective way of using the watchdog function can be considered.

A low-high-low WDI pulse within a given subroutine prevents the watchdog timing out. However, if the subroutine becomes stuck in an infinite loop, the watchdog could not detect this because the subroutine continues to toggle WDI. A more effective coding scheme for detecting this error involves using a slightly longer watchdog timeout. In the program that calls the subroutine, WDI is set high. The subroutine sets WDI low when it is called. If the program executes without error, WDI is toggled high and low with every loop of the program. If the subroutine enters an infinite loop, WDI is kept low, the watchdog times out, and the microprocessor is reset.

START

SET WDI

HIGH

PROGRAM

CODE

SUBROUTINE

SET WDI

LOW

RETURN

Figure 13. Watchdog Flow Diagram

RESET

INFINITE LOOP:

WATCHDOG

TIMES OUT

04534-0-020

TBD

ADM8616/7

GND

Figure 12. Ensuring Reset Valid to V

RESET

100k⍀

= 0 V

RESET

Rev. PrE | Page 8 of 10

ADM8616

WDI I/O

Figure 14. Typical Application Circuit

RESET

m P

Preliminary Technical Data ADM8616/ADM8617

OUTLINE DIMENSIONS

2.20

1.35

1.15

PIN 1

0.65 BSC

1.80

4 3

0.50 BSC

2.40

1.80

1.00

0.80

0.10 MAX

0.30

0.15

0.10 COPLANARITY

PACKAGE OUTLINE CORRESPONDS IN FULL TO EIAJ SC82

EXCEPT FOR WIDTH OF PIN-2 AS SHOWN

Figure 2. 4-Lead Plastic Surface Mount Package [SC70]

Dimensions shown in millimeters

0.70

0.50

1.10

0.80

SEATING PLANE

(KS-4)

0.18

0.10

0.30

0.10

Rev. PrE | Page 9 of 10

ADM8616/ADM8617 Preliminary Technical Data

blank

ORDERING GUIDE

ADM861_ _ _ _ _KS_-RL7

ORDERING QUANTITY RL7: 3,000 PIECE REEL

Z: LEAD FREE PACKAGE CODE

KS: 4-LEAD SC70 TEMPERATURE RANGE A: -40oC TO +85oC

WATCHDOG TIMEOUT PERIOD W: 6.3ms (typ) X: 102ms (typ) Y: 1.6s (typ) Z: 1120ms (typ)

RESET THRESHOLD NUMBER

L: 4.63V

M: 4.38V

T: 3.08V S: 2.93V R: 2.63V Z: 2.32V Y: 2.19V

W: 1.67V

V: 1.58V

GENERIC NUMBER

(6/7/8)

RESET TIMEOUT PERIOD

A: 1ms (min)

B: 20ms (min)

C: 140ms (min)

D: 1120ms (min)

Figure 3. Ordering Code Structure

Standard Models

Model1 Reset Threshold (V) Temperature Range Quantity Package Type Branding

ADM8616LCYAKSZ-RL7 4.63 -40°C to +85°C 3k SC70-4 N0F ADM8616MCYAKSZ-RL7 4.38 -40°C to +85°C 3k SC70-4 N0F ADM8616TCYAKSZ-RL7 3.08 -40°C to +85°C 3k SC70-4 N0F ADM8616SCYAKSZ-RL7 2.93 -40°C to +85°C 3k SC70-4 N0F ADM8616RCYAKSZ-RL7 2.63 -40°C to +85°C 3k SC70-4 N0F ADM8616ZCYAKSZ-RL7 2.32 -40°C to +85°C 3k SC70-4 N0F ADM8616YCYAKSZ-RL7 2.19 -40°C to +85°C 3k SC70-4 N0F ADM8616WCYAKSZ-RL7 1.67 -40°C to +85°C 3k SC70-4 N0F ADM8616VCYAKSZ-RL7 1.58 -40°C to +85°C 3k SC70-4 N0F

ADM8617RCYAKSZ-RL7 2.63 -40°C to +85°C 3k SC70-4 M4X

Complete the ordering code by inserting reset threshold, reset timeout and watchdog timeout suffixes. Contact Sales for availability of non-standard models.

PR04795-0-3/05(PrE)

Rev. PrE | Page 10 of 10

Datasheet ADM8616 Datasheet (Analog Devices)

Specifications and Main Features

Frequently Asked Questions

User Manual