Datasheet

ManualsBrandsANALOG DEVICES ManualsPMICsPMIC - system monitor Reset/power-on reset PDIP 8

Low Cost Microprocessor

Supervisory Circuits

ADM705/ADM706/ADM707/ADM708

Rev. G

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FEATURES

Guaranteed

RESET

valid with V

= 1 V

190 μA quiescent current

Precision supply voltage monitor

4.65 V (ADM705/ADM707)

4.40 V (ADM706/ADM708)

200 ms reset pulse width

Debounced TTL/CMOS manual reset input (

)

Independent watchdog timer (ADM705/ADM706)

1.60 sec timeout (ADM705/ADM706)

Active high reset output (ADM707/ADM708)

Voltage monitor for power-fail or low battery warning

Superior upgrade for MAX705 to MAX708

APPLICATIONS

Microprocessor systems

Computers

Controllers

Intelligent instruments

Critical microprocessor supply monitoring

FUNCTIONAL BLOCK DIAGRAMS

WATCHDOG

TRANSITION

DETECTOR

WATCHDOG

INPUT (WDI)

POWER-FAIL

INPUT (PFI)

POWER-FAIL

OUTPUT (PFO)

WATCHDOG

OUTPUT (WDO)

RESET

VOLTAGE REFERENCE = 4.65V (ADM705), 4.40V (ADM706)

ADM705/

ADM706

RESET AND

WATCHDOG

TIMEBASE

RESET

GENERATOR

250μA

WATCHDOG

TIMER

4.65V*

1.25V

00088-001

Figure 1. ADM705/ADM706

1.25V

POWER-FAIL

INPUT (PFI)

RESET

* VOLTAGE REFERENCE = 4.65V (ADM707), 4.40V (ADM708)

ADM707/

ADM708

RESET

GENERATOR

250μA

RESET

00088-002

4.65V*

POWER-FAIL

OUTPUT (PFO)

Figure 2. ADM707/ADM708

GENERAL DESCRIPTION

The ADM705/ADM706/ADM707/ADM708 microprocessor

supervisory circuits are suitable for monitoring 5 V power

supplies/batteries and can also monitor microprocessor activity.

The ADM705/ADM706 provide power-supply monitoring

circuitry that generate a reset output during power-up, power-

down, and brownout conditions. The reset output remains

operational with V

as low as 1 V. Independent watchdog

monitoring circuitry is also provided. This is activated if the

watchdog input has not been toggled within 1.60 seconds.

In addition, there is a 1.25 V threshold detector to warn of

power-failures, to detect low battery conditions, or to monitor an

additional power supply. An active low, debounced manual reset

input (

) is also included.

The ADM705 and ADM706 are identical except for the reset

threshold monitor levels, which are 4.65 V and 4.40 V, respectively.

The ADM707 and ADM708 provide a similar functionality to

the ADM705 and ADM706 and only differ in that a watchdog

timer function is not available. Instead, an active high reset

output (RESET) is available as well as the active low reset output

(

RESET

). The ADM707 and ADM708 are identical except for

the reset threshold monitor levels, which are 4.65 V and 4.40 V,

respectively.

All parts are available in narrow 8-lead PDIP and 8-lead SOIC

packages.

Summary of content (12 pages)

PAGE 1
Low Cost Microprocessor Supervisory Circuits ADM705/ADM706/ADM707/ADM708 FUNCTIONAL BLOCK DIAGRAMS WATCHDOG INPUT (WDI) WATCHDOG TRANSITION DETECTOR VCC 250μA MR 4.65V* ADM705/ ADM706 POWER-FAIL INPUT (PFI) WATCHDOG OUTPUT (WDO) RESET AND WATCHDOG TIMEBASE RESET GENERATOR VCC 1.25V RESET POWER-FAIL OUTPUT (PFO) * VOLTAGE REFERENCE = 4.65V (ADM705), 4.40V (ADM706) Figure 1.
PAGE 2
ADM705/ADM706/ADM707/ADM708 TABLE OF CONTENTS Features .............................................................................................. 1 Power-Fail RESET Output ...........................................................8 Applications ....................................................................................... 1 Manual Reset..................................................................................8 Functional Block Diagrams ..............................................
PAGE 3
ADM705/ADM706/ADM707/ADM708 SPECIFICATIONS VCC = 4.75 V to 5.5 V, TA = TMIN to TMAX, unless otherwise noted. Table 1. Parameter Min Typ Max Unit 190 5.5 250 V μA 4.75 4.50 V V mV ms V V V V V V sec ns Test Conditions/Comments POWER SUPPLY VCC Operating Voltage Range Supply Current 1.0 LOGIC OUTPUT Reset Threshold Reset Threshold Hysteresis RESET PULSE WIDTH RESET OUTPUT VOLTAGE 4.5 4.25 160 VCC − 1.5 4.65 4.40 40 200 280 0.4 0.3 0.3 RESET OUTPUT VOLTAGE VCC − 1.
PAGE 4
ADM705/ADM706/ADM707/ADM708 ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted. Table 2. Parameter VCC All Other Inputs Input Current VCC GND Digital Output Current Power Dissipation, N-8 PDIP θJA Thermal Impedance Power Dissipation, R-8 SOIC θJA Thermal Impedance Power Dissipation, RM-8 MSOP θJA Thermal Impedance Operating Temperature Range Industrial (Version A) Lead Temperature (Soldering, 10 sec) Vapor Phase (60 sec) Infrared (15 sec) Storage Temperature Range ESD Rating Rating −0.
PAGE 5
ADM705/ADM706/ADM707/ADM708 ADM705/ ADM706 8 MR 1 WDO VCC 2 7 RESET ADM707/ ADM708 8 RESET RESET 1 7 RESET RESET 2 MR 3 VCC 4 GND 3 6 NC TOP VIEW PFI 4 (Not to Scale) 5 PFO GND 3 00088-003 6 WDI TOP VIEW PFI 4 (Not to Scale) 5 PFO NC = NO CONNECT 00088-004 MR 1 VCC 2 Figure 4. ADM707/ADM708 PDIP/SOIC Pin Configuration Figure 3.
PAGE 6
ADM705/ADM706/ADM707/ADM708 TYPICAL PERFORMANCE CHARACTERISTICS VCC = 5V TA = 25°C A1 VCC 4.50V 1.3V PFI 100 1.2V 90 5V 10 0V 0% 1V 1V 500msH O 00088-012 RESET 500ns/DIV Figure 8. PFI Comparator Assertion Response Time Figure 6. RESET Output Voltage vs. Supply Voltage VCC = 5V TA = 25°C A1 VCC 4.50V 1.3V PFI 100 1.2V 90 RESET 4.4V PFO 10 1V 500msH O 00088-013 1V 00088-015 0V 0% 500ns/DIV Figure 7. ADM707/ADM708 RESET Output Voltage vs. Supply Voltage Rev.
PAGE 7
ADM705/ADM706/ADM707/ADM708 TA = 25°C 5V 5V 5V RESET RESET VCC 4V VCC = VRT TA = 25°C 5V RESET 0V 0V 2μs/DIV 100ns/DIV Figure 10. RESET, RESET Assertion Figure 12. ADM705/ADM707 RESET Response Time 5V 5V RESET RESET VCC = VRT TA = 25°C 0V 00088-017 0V 100ns/DIV Figure 11. RESET, RESET Deassertion Rev.
PAGE 8
ADM705/ADM706/ADM707/ADM708 CIRCUIT INFORMATION RESET is an active low output that provides a reset signal to the microprocessor whenever the VCC input is below the reset threshold. An internal timer holds RESET low for 200 ms after the voltage on VCC rises above the threshold. This functions as a power-on reset signal for the microprocessor. It allows time for both the power supply and the microprocessor to stabilize after power-up.
PAGE 9
ADM705/ADM706/ADM707/ADM708 Adding Hysteresis to the Power-Fail Comparator VALID RESET BELOW 1 V VCC For increased noise immunity, hysteresis can be added to the power-fail comparator. Because the comparator circuit is noninverting, hysteresis can be added simply by connecting a resistor between the PFO output and the PFI input, as shown in Figure 16. The ADM705/ADM706/ADM707/ADM708 are guaranteed to provide a valid reset level with VCC as low as 1 V (see the Typical Performance Characteristics section).
PAGE 10
ADM705/ADM706/ADM707/ADM708 APPLICATIONS INFORMATION A typical application circuit is shown in Figure 18. The unregulated dc input supply is monitored using PFI via the resistive divider network. Resistor R1 and Resistor R2 should be selected so that when the supply voltage drops below the desired level (such as 8 V), the voltage on PFI drops below the 1.25 V threshold, thereby generating an interrupt to the microprocessor.
PAGE 11
ADM705/ADM706/ADM707/ADM708 OUTLINE DIMENSIONS 0.400 (10.16) 0.365 (9.27) 0.355 (9.02) 8 5 1 4 0.280 (7.11) 0.250 (6.35) 0.240 (6.10) 0.325 (8.26) 0.310 (7.87) 0.300 (7.62) PIN 1 0.100 (2.54) BSC 0.060 (1.52) MAX 0.210 (5.33) MAX 0.150 (3.81) 0.130 (3.30) 0.115 (2.92) 0.195 (4.95) 0.130 (3.30) 0.115 (2.92) 0.015 (0.38) MIN 0.015 (0.38) GAUGE PLANE SEATING PLANE 0.022 (0.56) 0.018 (0.46) 0.014 (0.36) 0.005 (0.13) MIN 0.430 (10.92) MAX 0.014 (0.36) 0.010 (0.25) 0.008 (0.20) 0.070 (1.78) 0.
PAGE 12
ADM705/ADM706/ADM707/ADM708 ORDERING GUIDE Model ADM705AN ADM705ANZ 1 ADM705AR ADM705AR–REEL ADM705AR–REEL7 ADM705ARZ1 ADM705ARZ–REEL1 ADM705ARZ–REEL71 ADM706AN ADM706ANZ1 ADM706AR ADM706AR-REEL ADM706AR-REEL7 ADM706ARZ1 ADM706ARZ-REEL1 ADM706ARZ-REEL71 ADM707AN ADM707ANZ1 ADM707AR ADM707AR-REEL ADM707ARZ1 ADM707ARZ-REEL1 ADM708AN ADM708ANZ1 ADM708AR ADM708AR-REEL ADM708ARZ1 ADM708ARZ-REEL1 ADM708ARM ADM708ARM-REEL ADM708ARMZ1 ADM708ARMZ-REEL1 1 Temperature Range −40°C to +85°C −40°C to +85°C −40°C to +85°