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Microprocessor

Supervisory Circuits

Data Sheet

ADM8690/ADM8691/ADM8695

Rev. C

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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

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FEATURES

Upgrade for the ADM690, ADM691, ADM695 and

for the MAX690, MAX691, MAX695

Specified over temperature

Low power consumption: 0.7 mW

Precision voltage monitor

Reset assertion down to 1 V V

Low switch on resistance: 0.7 Ω normal, 7 Ω in backup

High current drive: 100 mA

Watchdog timer: 100 ms, 1.6 sec, or adjustable

Standby current: 400 nA

Automatic battery backup power switching

Extremely fast gating of chip enable signals (3 ns)

Voltage monitor for power fail

Available in TSSOP package

APPLICATIONS

Microprocessor systems

Computers

Controllers

Intelligent instruments

Automotive systems

PRODUCT HIGHLIGHTS

The ADM8690 is available in 8-lead PDIP and SOIC packages

and provides the following functions:

1. Power-on reset output during power-up, power-down,

and brownout conditions. The

RESET

output remains

operational with V

as low as 1 V.

2. Battery backup switching for CMOS RAM, CMOS micro-

processor, or other low power logic.

3. Reset pulse if the optional watchdog timer is not toggled

within a specified time.

4. 1.3 V threshold detector for power-fail warning, low battery

detection, or to monitor a power supply other than 5 V.

The ADM8691 and ADM8695 are available in 16-lead PDIP

and small outline packages (including TSSOP) and provide

three additional functions:

1. Write protection of CMOS RAM or EEPROM.

2. Adjustable reset and watchdog timeout periods.

3. Separate watchdog timeout, backup battery switchover, and

low V

status outputs.

FUNCTIONAL BLOCK DIAGRAMS

RESET

1.3V

RESET

GENERATOR

WATCHDOG

TRANSITION DETECTOR

(1.6sec)

4.65V

ADM8690

WATCHDOG

INPUT (WDI)

POWER-FAIL

INPUT (PFI)

BATT

OUT

OUTPUT (PFO)

VOLTAGE DETECTOR = 4.65V

RESET PULSE WIDTH = 50ms

00093-001

Figure 1. ADM8690

1.3V

LOW LINE

RESET

OSC IN

OSC SEL

TT ON

ADM8691/

ADM8695

4.65V

RESET AND

WATCHDOG

TIME BASE

RESET

GENERATOR

WATCHDOG

TRANSITION DETECTOR

WATCHDOG

TIMER

POWER-FAIL

INPUT (PFI)

WATCHDOG

INPUT (WDI)

BATT

OUT

POWER-FAIL

OUTPUT (PFO)

WATCHDOG

OUTPUT (WDO)

OUT

VOLTAGE DETECTOR = 4.65V

00093-002

Figure 2. ADM8691/ADM8695

Summary of content (24 pages)

PAGE 1
FEATURES FUNCTIONAL BLOCK DIAGRAMS VBATT VOUT VCC RESET GENERATOR 2 4.65V 1 WATCHDOG INPUT (WDI) WATCHDOG TRANSITION DETECTOR (1.6sec) PRODUCT HIGHLIGHTS POWER-FAIL OUTPUT (PFO) 1.3V 1VOLTAGE DETECTOR = 4.65V 2RESET PULSE WIDTH = 50ms Figure 1. ADM8690 BATT ON 2. 3. 4. Power-on reset output during power-up, power-down, and brownout conditions. The RESET output remains operational with VCC as low as 1 V. Battery backup switching for CMOS RAM, CMOS microprocessor, or other low power logic.
PAGE 2
ADM8690/ADM8691/ADM8695 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Power-Fail Warning Comparator ............................................. 14 Applications ....................................................................................... 1 Applications Information .............................................................. 15 Product Highlights .......................................................
PAGE 3
Data Sheet ADM8690/ADM8691/ADM8695 GENERAL DESCRIPTION The ADM8690/ADM8691/ADM8695 supervisory circuits offer complete single-chip solutions for power supply monitoring and battery control functions in microprocessor systems. These functions include microprocessor reset, backup battery switchover, watchdog timer, CMOS RAM write protection, and power failure warning. The complete family provides a variety of configurations to satisfy most microprocessor system requirements.
PAGE 4
ADM8690/ADM8691/ADM8695 Data Sheet SPECIFICATIONS VCC = full operating range, VBATT = 2.8 V, TA = TMIN to TMAX, unless otherwise noted. Table 2.
PAGE 5
Data Sheet Parameter CHIP ENABLE GATING CEIN Threshold ADM8690/ADM8691/ADM8695 Min Typ Max Unit Test Conditions/Comments 0.8 V V μA V V V ns VIL VIH 3.0 3 CEIN Pull-Up Current CEOUT Output Voltage 0.4 VOUT − 1.5 VOUT − 0.
PAGE 6
ADM8690/ADM8691/ADM8695 Data Sheet ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted. Table 3.
PAGE 7
Data Sheet ADM8690/ADM8691/ADM8695 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS VBATT 1 16 RESET VOUT 2 15 RESET VCC 3 GND 4 13 CEIN TOP VIEW 12 CEOUT (Not to Scale) 11 WDI LOW LINE 6 8 VBATT ADM8690 7 RESET TOP VIEW (Not to Scale) 6 WDI 5 PFO PFI 4 BATT ON 5 OSC IN 7 00093-003 VCC 2 GND 3 14 WDO OSC SEL 8 Figure 3. ADM8690 Pin Configuration, 8-Lead PDIP and 8-Lead SOIC_N 10 PFO 9 PFI 00093-004 VOUT 1 ADM8691/ ADM8695 Figure 4.
PAGE 8
ADM8690/ADM8691/ADM8695 8-Lead 7 N/A Pin No. 16-Lead 15 16 Mnemonic RESET RESET Data Sheet Description Logic Output. RESET goes low if VCC falls below the reset threshold or if the watchdog timer is not serviced within its timeout period. The reset threshold is typically 4.65 V. RESET remains low for 50 ms (ADM8690/ADM8691) or 200 ms (ADM8695) after VCC returns above the threshold.
PAGE 9
Data Sheet ADM8690/ADM8691/ADM8695 TYPICAL PERFORMANCE CHARACTERISTICS 1.315 5.00 1.310 PFI INPUT THRESHOLD (V) 4.99 4.97 4.96 4.95 1.300 1.295 1.290 1.285 20 30 40 50 60 IOUT (mA) 70 80 90 100 1.280 –60 00093-015 4.94 10 1.305 –30 0 30 60 TEMPERATURE (°C) 90 00093-018 VOUT (V) 4.98 120 Figure 8. PFI Input Threshold vs. Temperature Figure 5. VOUT vs. IOUT, Normal Operation 2.800 53 VCC = 5V RESET ACTIVE TIME (ms) 2.798 2.794 2.792 2.
PAGE 10
ADM8690/ADM8691/ADM8695 6 6 VCC = 5V TA = 25°C PFO 5 4 4 3 3 VPFI PFO 2 1.3V 30pF 1 0 0 PFI 1.25 0.1 0.2 0.3 0.4 0.5 TIME (µs) 0.6 0.7 00093-021 0 0.8 Figure 11. Power-Fail Comparator Response Time, Falling 5 1.3V PFO 30pF VCC = 5V TA = 25°C 2 VPFI 1 1.3V PFO 30pF PFO 1.35 10 20 30 40 50 TIME (µs) 60 70 80 90 00093-022 PFI 0 PFI 0.2 0.4 0.6 0.8 1.0 TIME (µs) 1.2 1.4 1.6 1.8 Figure 13. Power-Fail Comparator Response Time with Pull-Up Resistor 3 1.
PAGE 11
Data Sheet ADM8690/ADM8691/ADM8695 CIRCUIT INFORMATION BATTERY SWITCHOVER SECTION The battery switchover circuit compares VCC to the VBATT input and connects VOUT to whichever is higher. Switchover occurs when VCC is 50 mV higher than VBATT as VCC falls, and when VCC is 70 mV greater than VBATT as VCC rises. This 20 mV hysteresis prevents repeated rapid switching if VCC falls very slowly or remains nearly equal to the battery voltage.
PAGE 12
ADM8690/ADM8691/ADM8695 Data Sheet WATCHDOG TIMER RESET WDI The nominal watchdog timeout period is preset at 1.6 sec on the ADM8690. The ADM8691/ADM8695 can be configured for a fixed timeout period—short (100 ms) or long (1.6 sec)—or for an adjustable timeout period.
PAGE 13
Data Sheet ADM8690/ADM8691/ADM8695 WATCHDOG OUTPUT (WDO) (ADM8691/ADM8695) The watchdog output (WDO pin on the ADM8691/ADM8695) provides a status output that goes low if the watchdog timer times out and remains low until set high by the next transition on the watchdog input. WDO is also set high when VCC goes below the reset threshold. OSC SEL ADM8691/ ADM8695 CLOCK 0 TO 500kHz OSC IN 00093-008 7 Figure 17.
PAGE 14
ADM8690/ADM8691/ADM8695 Data Sheet PFO is normally used to interrupt the microprocessor so that data can be stored in RAM and the shutdown procedure executed before power is lost. POWER-FAIL WARNING COMPARATOR An additional comparator is provided for early warning of failure in the microprocessor power supply. The power-fail input (PFI) is compared to an internal 1.3 V reference. The power-fail output (PFO) goes low when the voltage at PFI is less than 1.3 V.
PAGE 15
Data Sheet ADM8690/ADM8691/ADM8695 APPLICATIONS INFORMATION INCREASING THE DRIVE CURRENT If the continuous output current requirements at VOUT exceed 100 mA, or if a lower VCC − VOUT voltage differential is desired, an external PNP pass transistor can be connected in parallel with the internal transistor. The BATT ON output (ADM8691/ ADM8695) can directly drive the base of the external transistor. 7V TO 15V INPUT POWER 7805 5V VCC R1 R4 1.3V PFO PFI TO MICROPROCESSOR NMI R2 R3 PNP TRANSISTOR 0.
PAGE 16
ADM8690/ADM8691/ADM8695 Data Sheet WATCHDOG STROBE CONTROL INPUT WDI ADM8690/ ADM8691/ ADM8695 00093-028 The watchdog feature can be enabled and disabled under program control by driving WDI with a three-state buffer (see Figure 28). When three-stated, the WDI input floats, thereby disabling the watchdog timer. Figure 28. Enabling and Disabling the Watchdog Input For the ADM8691/ADM8695, the watchdog period can be extended under program control using the circuit shown in Figure 29.
PAGE 17
Data Sheet ADM8690/ADM8691/ADM8695 TYPICAL APPLICATIONS Figure 31 shows a similar application, but in this case the PFI input monitors the unregulated input to the 7805 voltage regulator. This circuit provides an earlier warning of an impending power failure. It is useful with processors that operate at low speeds or where there are a significant number of housekeeping tasks to be completed before the power is lost.
PAGE 18
ADM8690/ADM8691/ADM8695 Data Sheet RESET OUTPUT RAM WRITE PROTECTION The internal voltage detector monitors VCC and generates a RESET output to hold the microprocessor reset line low when VCC is below 4.65 V. An internal timer holds RESET low for 50 ms (200 ms for the ADM8695) after VCC rises above 4.65 V. This prevents repeated toggling of RESET, even if the 5 V power drops out and recovers with each power line cycle. The ADM8691/ADM8695 CEOUT line drives the chip select inputs of the CMOS RAM.
PAGE 19
Data Sheet ADM8690/ADM8691/ADM8695 OUTLINE DIMENSIONS 0.400 (10.16) 0.365 (9.27) 0.355 (9.02) 8 5 1 0.280 (7.11) 0.250 (6.35) 0.240 (6.10) 4 0.100 (2.54) BSC 0.325 (8.26) 0.310 (7.87) 0.300 (7.62) 0.060 (1.52) MAX 0.210 (5.33) MAX 0.015 (0.38) MIN 0.150 (3.81) 0.130 (3.30) 0.115 (2.92) SEATING PLANE 0.022 (0.56) 0.018 (0.46) 0.014 (0.36) 0.195 (4.95) 0.130 (3.30) 0.115 (2.92) 0.015 (0.38) GAUGE PLANE 0.430 (10.92) MAX 0.005 (0.13) MIN 0.014 (0.36) 0.010 (0.25) 0.008 (0.20) 0.070 (1.78) 0.
PAGE 20
ADM8690/ADM8691/ADM8695 Data Sheet 0.800 (20.32) 0.790 (20.07) 0.780 (19.81) 16 9 1 0.280 (7.11) 0.250 (6.35) 0.240 (6.10) 8 0.325 (8.26) 0.310 (7.87) 0.300 (7.62) 0.100 (2.54) BSC 0.060 (1.52) MAX 0.210 (5.33) MAX 0.195 (4.95) 0.130 (3.30) 0.115 (2.92) 0.015 (0.38) MIN 0.150 (3.81) 0.130 (3.30) 0.115 (2.92) 0.015 (0.38) GAUGE PLANE SEATING PLANE 0.022 (0.56) 0.018 (0.46) 0.014 (0.36) 0.430 (10.92) MAX 0.005 (0.13) MIN 0.014 (0.36) 0.010 (0.25) 0.008 (0.20) 0.070 (1.78) 0.060 (1.52) 0.
PAGE 21
Data Sheet ADM8690/ADM8691/ADM8695 10.00 (0.3937) 9.80 (0.3858) 4.00 (0.1575) 3.80 (0.1496) 9 16 1 6.20 (0.2441) 5.80 (0.2283) 8 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 0.50 (0.0197) 0.25 (0.0098) 1.75 (0.0689) 1.35 (0.0531) SEATING PLANE 0.51 (0.0201) 0.31 (0.0122) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.
PAGE 22
ADM8690/ADM8691/ADM8695 Data Sheet ORDERING GUIDE Model 1 ADM8690AN ADM8690ANZ ADM8690ARN ADM8690ARN-REEL ADM8690ARNZ ADM8691ANZ ADM8691ARN ADM8691ARN-REEL ADM8691ARNZ ADM8691ARW ADM8691ARW-REEL ADM8691ARWZ ADM8691ARU ADM8691ARU-REEL ADM8691ARUZ ADM8695ARW ADM8695ARW-REEL ADM8695ARWZ 1 Temperature Range −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to
PAGE 23
Data Sheet ADM8690/ADM8691/ADM8695 NOTES Rev.
PAGE 24
ADM8690/ADM8691/ADM8695 Data Sheet NOTES ©2006–2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D00093-0-12/11(C) Rev.