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MAX6366HKA29-T中文资料

General Description

The MAX6365–MAX6368 supervisory circuits simplify power-supply monitoring, battery-backup control func-tions, and memory write protection in microprocessor (μP) systems. The circuits significantly improve the size,accuracy, and reliability of modern systems with an ultra-small integrated solution.

These devices perform four basic system functions:1) Provide a μP reset output during V CC supply power-up, power-down, and brownout conditions.

2) Internally control V CC to backup-battery switching to

maintain data or low-power operation for CMOS RAM, CMOS μPs, real-time clocks, and other digital logic when the main supply fails.

3) Provide memory write protection through internal

chip-enable gating during supply or processor faults.4) Include one of the following options: a manual reset

input (MAX6365), a watchdog timer function (MAX6366), a battery-on output (MAX6367), or an auxiliary user-adjustable reset input (MAX6368).

The MAX6365–MAX6368 operate from V CC supply volt-ages as low as 1.2V. The factory preset reset threshold voltages range from 2.32V to 4.63V (see Ordering Information ). In addition, each part is offered in three reset output versions: push-pull active low, open-drain active low, or open-drain active high (see Selector Guide ). The MAX6365–MAX6368 are available in minia-ture 8-pin SOT23 packages.

Applications

Critical μP/μC Power Portable/Battery-Monitoring Powered Equipment Fax Machines Set-Top Boxes Industrial Control POS Equipment

Computers/Controllers

Features

o Low +1.2V Operating Supply Voltage (V CC or V BATT )o Precision Monitoring of +5.0V, +3.3V, +3.0V, and +2.5V Power-Supply Voltages

o On-Board Gating of Chip-Enable Signals, 1.5ns Propagation Delay

o Debounced Manual Reset Input (MAX6365)o Watchdog Timer, 1.6s Timeout (MAX6366)o Battery-On Output Indicator (MAX6367)

o Auxiliary User-Adjustable RESET IN (MAX6368)o Low 10μA Quiescent Supply Current o Three Available Output Structures

Push-Pull RESET Open-Drain RESET Open-Drain RESET

o RESET/RESET Valid Down to 1.2V Guaranteed (V CC or V BATT )

o Power-Supply Transient Immunity o 150ms min Reset Timeout Period o Miniature 8-Pin SOT23 Package

MAX6365–MAX6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating

________________________________________________________________Maxim Integrated Products

Pin Configurations

19-1658; Rev 1; 6/01

For pricing, delivery, and ordering information,please contact Maxim/Dallas Direct!at 1-888-629-4642, or visit Maxim’s website at https://www.wendangku.net/doc/192920736.html,.

Ordering Information

*These parts offer a choice of reset threshold voltages. From the Reset Threshold Ranges table, insert the desired threshold volt-age code in the blank to complete the part number. SOT parts come in tape-and-reel only and must be ordered in 2500-piece increments. See Device Marking Codes for a complete parts list,including SOT top marks and standard threshold versions. See Selector Guide for a listing of device features.

Typical Operating Circuit appears at end of data sheet.

M A X 6365–M A X 6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V = +2.4V to +5.5V, V = +3.0V, CE IN = V , reset not asserted, T = -40°C to +85°C. Typical values are at T = +25°C,Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Terminal Voltages (with respect to GND)

V CC , BATT, OUT.......................................................-0.3V to +6V RESET (open drain), RESET (open drain)................-0.3V to +6V BATT ON, RESET (push-pull), RESET IN,

WDI, CE IN, CE OUT...........................-0.3V to (V OUT + 0.3V)MR ..............................................................-0.3V to (V CC + 0.3V)Input Current

V CC Peak ..............................................................................1A V CC Continuous.............................................................250mA BATT Peak.....................................................................250mA BATT Continuous.............................................................40mA

GND...............................................................................75mA Output Current

OUT...............................Short-Circuit Protected for up to 10s RESET, RESET , BATT ON, CE OUT...............................20mA Continuous Power Dissipation (T A = +70°C)

8-Pin SOT23 (derate 8.75mW/°C above +70°C)........700mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range.............................-65°C to +150°C Junction Temperature .....................................................+150°C Lead Temperature (soldering, 10s).................................+300°C

MAX6365–MAX6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating

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ELECTRICAL CHARACTERISTICS (continued)

(V CC = +2.4V to +5.5V, V BATT = +3.0V, CE IN = V CC , reset not asserted, T A = -40°C to +85°C. Typical values are at T A = +25°C,

M A X 6365–M A X 6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating 4_______________________________________________________________________________________

Typical Operating Characteristics

(T A = +25°C, unless otherwise noted.)

109121115141316-400-2020406080SUPPLY CURRENT

vs. TEMPERATURE (NO LOAD)

TEMPERATURE (°C)S U P P L Y C U R R E N T (μA )

0.20.6

0.40.81.01.2

BATTERY SUPPLY CURRENT (BACKUP MODE) vs. TEMPERATURE

TEMPERATURE (°C)

B A T T E R Y S U P P L Y

C U R R E N T (μA )

-402040-2006080

437658

-40

-20

BATT-TO-OUT ON-RESISTANCE

vs. TEMPERATURE

TEMPERATURE (°C)

B A T T -T O -O U T O N -R E S I S T A N

C E (?)

ELECTRICAL CHARACTERISTICS (continued)

= +2.4V to +5.5V, V = +3.0V, CE IN = V , reset not asserted, T = -40°C to +85°C. Typical values are at T = +25°C,Note 2:V BATT can be 0 anytime, or V CC can go down to 0 if V BATT is active (except at startup).Note 3:RESET is pulled up to OUT. Specifications apply for OUT = V CC or OUT = BATT.Note 4:The chip-enable resistance is tested with V CC = V TH(MAX)and CE IN = V CC /2.

MAX6365–MAX6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating

_______________________________________________________________________________________5

Typical Operating Characteristics (continued)

(T A = +25°C, unless otherwise noted.)

00.40.20.80.61.21.01.4-40

-20

V CC TO OUT ON-RESISTANCE

vs. TEMPERATURE

TEMPERATURE (°C)V C C T O O U T O N -R E S I S T A N C E (?)

190

195

205

200

210

RESET TIMEOUT PERIOD vs. TEMPERATURE

M A X 6365/8-05

TEMPERATURE (°C)

R E S E T T I M E O U T P E R I O D (m s )

-40

-20

3015

756045135

12010590TEMPERATURE (°C)

P R O P A G A T I O N D E L A Y (μs )-40

-20

V CC vs. TEMPERATURE

2.03.0

2.55.0

4.54.03.5RESET THRESHOLD vs. TEMPERATURE

TEMPERATURE (°C)

T H R E S H O L D (V )

-40

-20

100

1000

10,000MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE

RESET THRESHOLD OVERDRIVE V TH - V CC (mV)M A X I M U M T R A N S I E N T D U R A T I O N (μs )

4003003502502000501501000

32154987610

00.5 1.0 1.5 2.0 2.5 3.0 3.5

BATTERY SUPPLY CURRENT vs. SUPPLY VOLTAGE

V CC (V)

B A T T E R Y S U P P L Y

C U R R E N T (μA )

M A X 6365–M A X 6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating 6_______________________________________________________________________________________

1.234

1.235

1.236MAX6368

RESET IN THRESHOLD vs. TEMPERATURE

M A X 6365/8 -10

TEMPERATURE (°C)

V R T H (V )

-40

-20

1.01.91.61.3

2.82.52.2MAX6368

RESET IN TO RESET PROPAGATION DELAY

vs. TEMPERATURE

TEMPERATURE (°C)

P R O P A G A T I O N D E L A Y (μs )

-40

-20

C LOA

D (pF)

P R O P A G A T I O N D E L A Y (n s )

10050

150

200

CHIP-ENABLE PROPAGATION DELAY vs. CE OUT LOAD CAPACITANCE

25-40

-20

TEMPERATURE (°C)C E I N T O C E O U T O N -R E S I S T A N C E (?)

CE IN TO CE OUT ON-RESISTANCE

vs. TEMPERATURE

1.0

1.31.21.11.51.41.91.81.71.6

2.0

-40

-20

TEMPERATURE (°C)

W A T C H D O G T I M E O U T P E R I O D (s )MAX6366

WATCHDOG TIMEOUT PERIOD

vs. TEMPERATURE

Typical Operating Characteristics (continued)

(T A = +25°C, unless otherwise noted.)

MAX6365–MAX6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating

_______________________________________________________________________________________7

M A X 6365–M A X 6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating 8

_______________________________________________________________________________________

Detailed Description

The Typical Operating Circuit shows a typical connec-tion for the MAX6365–MAX6368. OUT powers the static random-access memory (SRAM). If V CC is greater than the reset threshold (V TH ), or if V CC is lower than V TH but higher than V BATT , V CC is connected to OUT. If V CC is lower than V TH and V CC is less than V BATT ,BATT is connected to OUT. OUT supplies up to 150mA from V CC . In battery-backup mode, an internal MOSFET connects the backup battery to OUT. The on-resistance of the MOSFET is a function of backup-battery voltage and is shown in the BATT-to-OUT On-Resistance vs.Temperature graph in the T ypical Operating Char-acteristics .

Chip-Enable Signal Gating

The MAX6365–MAX6368 provide internal gating of CE signals to prevent erroneous data from being written to

CMOS RAM in the event of a power failure. During nor-mal operation, the CE gate is enabled and passes all CE transitions. When reset asserts, this path becomes disabled, preventing erroneous data from corrupting the CMOS RAM. All of these devices use a series trans-mission gate from CE IN to CE OUT. The 2ns propaga-tion delay from CE IN to CE OUT allows the devices to be used with most μPs and high-speed DSPs.

During normal operation, CE IN is connected to CE OUT through a low on-resistance transmission gate.This is valid when reset is not asserted. If CE IN is high when reset is asserted, CE OUT remains high regard-less of any subsequent transitions on CE IN during the reset event.

If CE IN is low when reset is asserted, CE OUT is held low for 12μs to allow completion of the read/write oper-ation (F igure 1). After the 12μs delay expires, the CE

Functional Diagram

MAX6365–MAX6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating

_______________________________________________________________________________________

OUT goes high and stays high regardless of any sub-sequent transitions on CE IN during the reset event.When CE OUT is disconnected from CE IN, CE OUT is actively pulled up to OUT.

The propagation delay through the chip-enable circuit-ry depends on both the source impedance of the drive to CE IN and the capacitive loading at CE OUT. The chip-enable propagation delay is production tested from the 50% point of CE IN to the 50% point of CE OUT, using a 50?driver and 50pF load capacitance.Minimize the capacitive load at CE OUT to minimize propagation delay, and use a low-output-impedance driver.

Backup-Battery Switchover

In a brownout or power failure, it may be necessary to preserve the contents of the RAM. With a backup bat-tery installed at BATT, the MAX6365–MAX6368 auto-matically switch the RAM to backup power when V CC falls. The MAX6367 has a BATT ON output that goes high in battery-backup mode. These devices require two conditions before switching to battery-backup mode:

1) V CC must be below the reset threshold.2) V CC must be below V BATT .

Table 1 lists the status of the inputs and outputs in bat-tery-backup mode. The devices do not power up if the

only voltage source is on BATT. OUT only powers up from V CC at startup.

Many μP-based products require manual reset capabili-ty, allowing the user or external logic circuitry to initiate a reset. For the MAX6365, a logic low on MR asserts reset.Reset remains asserted while MR is low and for a mini-mum of 150ms (t RP ) after it returns high. MR has an inter-nal 20k ?pullup resistor to V CC . This input can be driven with TTL/CMOS logic levels or with open-drain/collector outputs. Connect a normally open momentary switch from MR to GND to create a manual reset function; exter-nal debounce circuitry is not required. If MR is driven from long cables or the device is used in a noisy environ-ment, connect a 0.1μF capacitor from MR to GND to pro-vide additional noise immunity.

Figure 1. Reset and Chip-Enable Timing

M A X 6365–M A X 6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating 10

______________________________________________________________________________________

Watchdog Input (MAX6366 Only)

The watchdog monitors μP activity through the watch-dog input (WDI). If the μP becomes inactive, reset asserts. To use the watchdog function, connect WDI to a bus line or μP I/O line. A change of state (high to low,low to high, or a minimum 100ns pulse) resets the watchdog timer. If WDI remains high or low for longer than the watchdog timeout period (t WD ), the internal watchdog timer runs out and a reset pulse is triggered for the reset timeout period (t RP ). The internal watchdog timer clears whenever reset asserts or whenever WDI sees a rising or falling edge. If WDI remains in either a high or low state, a reset pulse asserts periodically after every t WD (F igure 2). Leave WDI unconnected to dis-able the watchdog function.

BATT ON Indicator (MAX6367 Only)

BATT ON is a push-pull output that drives high when in battery-backup mode. BATT ON typically sinks 3.2mA at 0.1V saturation voltage. In battery-backup mode, this terminal sources approximately 10μA from OUT. Use BATT ON to indicate battery-switchover status or to supply base drive to an external pass transistor for higher current applications (Figure 3).

RESET IN Comparator (MAX6368 Only)

RESET IN is compared to an internal 1.235V reference.If the voltage at RESET IN is less than 1.235V, reset asserts. Use the RESET IN comparator as an undervolt-age detector to signal a failing power supply or as a secondary power-supply reset monitor.

To program the reset threshold (V RTH ) of the secondary power supply, use the following (see Typical Operating Circuit ):

V RTH = V REF (R1 / R2 + 1)

where V REF = 1.235V. To simplify the resistor selection,choose a value for R2 and calculate R1:

R1 = R2 [(V RTH / V REF ) - 1]

Since the input current at RESET IN is 25nA (max),large values (up to 1M ?) can be used for R2 with no significant loss in accuracy. For example, in the Typical Operating Circuit , the MAX6368 monitors two supply voltages. To monitor the secondary 5V logic or analog supply with a 4.60V nominal programmed reset thresh-old, choose R2 = 100k ?, and calculate R1 = 273k ?.

Reset Output

A μP ’s reset input starts the μP in a known state. The MAX6365–MAX6368 μP supervisory circuits assert a reset to prevent code-execution errors during power-up, power-down, and brownout conditions. RESET is guaranteed to be a logic low or logic high, depending on the device chosen (see Ordering Information ).RESET or RESET asserts when V CC is below the reset threshold and for at least 150ms (t RP ) after V CC rises above the reset threshold. RESET or RESET also asserts when MR is low (MAX6365) and when RESET IN is less than 1.235V (MAX6368). The MAX6366 watch-dog function will cause RESET (or RESET ) to assert in pulses following a watchdog timeout (Figure 2).

Applications Information

Operation Without

a Backup Power Source

The MAX6365–MAX6368 provide battery-backup func-tions. If a backup power source is not used, connect BATT to GND and OUT to V CC .

Watchdog Software Considerations

One way to help the watchdog timer monitor the soft-ware execution more closely is to set and reset the watchdog at different points in the program rather than pulsing the watchdog input periodically. F igure 4shows a flow diagram in which the I/O driving the

Figure 2. MAX6366 Watchdog Timeout Period and Reset Active Time

MAX6365–MAX6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating

______________________________________________________________________________________11

watchdog is set low in the beginning of the program,set high at the beginning of every subroutine or loop,and set low again when the program returns to the beginning. If the program should hang in any subrou-tine, the problem would be quickly corrected.

Replacing the Backup Battery

When V CC is above V TH , the backup power source can be removed without danger of triggering a reset pulse.The device does not enter battery-backup mode when V CC stays above the reset threshold voltage.

Negative-Going V CC Transients

These supervisors are relatively immune to short-dura-tion, negative-going V CC transients. Resetting the μP when V CC experiences only small glitches is usually not desirable.

The T ypical Operating Characteristics section has a Maximum Transient Duration vs. Reset Threshold Overdrive graph for which reset is not asserted. The graph was produced using negative-going V CC pulses,

starting at V CC and ending below the reset threshold by the magnitude indicated (reset threshold overdrive).The graph shows the maximum pulse width that a neg-ative-going V CC transient can typically have without triggering a reset pulse. As the amplitude of the tran-sient increases (i.e., goes further below the reset threshold), the maximum allowable pulse width decreases. Typically, a V CC transient that goes 100mV below the reset threshold and lasts for 30μs will not trig-ger a reset pulse.

A 0.1μF bypass capacitor mounted close to the V CC pin provides additional transient immunity.

M A X 6365–M A X 6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating 12______________________________________________________________________________________

standard versions only. Contact factory for availability of nonstandard versions.

MAX6365–MAX6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating

______________________________________________________________________________________13

Pin Configurations (continued)

M A X 6365–M A X 6368

SOT23, Low-Power μP Supervisory Circuits with Battery Backup and Chip-Enable Gating 14______________________________________________________________________________________

Typical Operating Circuit

Chip Information

TRANSISTOR COUNT: 729PROCESS: CMOS

SOT23, Low-Power μP Supervisory Circuits

with Battery Backup and Chip-Enable Gating

MAX6365–MAX6368

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________15

?2001 Maxim Integrated Products Printed USA

is a registered trademark of Maxim Integrated Products.

Package Information