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MAX6419UK27+T中文资料

MAX6419UK27+T中文资料
MAX6419UK27+T中文资料

General Description

The MAX6412–MAX6420 low-power microprocessor supervisor circuits monitor system voltages from 1.6V to 5V. These devices are designed to assert a reset signal whenever the V CC supply voltage or RESET IN falls below its reset threshold or the manual reset input is asserted.The reset output remains asserted for the reset timeout period after V CC and RESET IN rise above the reset threshold and the manual reset input is deasserted. The reset timeout is externally set by a capacitor to provide more flexibility.

The MAX6412/MAX6413/MAX6414 feature fixed thresholds from 1.575V to 5V in approximately 100mV increments and a manual reset input. The MAX6415/MAX6416/MAX6417are offered with an adjustable reset input that can monitor voltages down to 1.26V and the MAX6418/MAX6419/MAX6420 are offered with one fixed input and one adjustable input to monitor dual-voltage systems.

The MAX6412/MAX6415/MAX6418 have an active-low,push-pull reset output. The MAX6413/MAX6416/MAX6419 have an active-high, push-pull reset output and the MAX6414/MAX6417/MAX6420 have an active-low, open-drain reset output. All of these devices are offered in a SOT23-5 package and are fully specified from -40°C to +125°C.

Applications

Automotive Medical Equipment Intelligent Instruments Portable Equipment

Battery-Powered Computers/Controllers Embedded Controllers Critical μP Monitoring Set-Top Boxes Computers

Features

?Monitor System Voltages from 1.6V to 5V ?Capacitor-Adjustable Reset Timeout Period ?Manual Reset Input (MAX6412/MAX6413/MAX6414)?Adjustable Reset Input Option (MAX6415–MAX6420)?Dual-Voltage Monitoring

(MAX6418/MAX6419/MAX6420)?Low Quiescent Current (1.7μA, typ)?3 RESET Output Options

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

?Guaranteed Reset Valid to V CC = 1V ?Power-Supply Transient Immunity ?Small SOT23-5 Packages

MAX6412–MAX6420

Low-Power, Single/Dual-Voltage μP Reset Circuits with Capacitor-Adjustable Reset Timeout Delay

________________________________________________________________Maxim Integrated Products

1

Ordering Information

Pin Configuration

19-2336; Rev 2; 12/05

For pricing, delivery, and ordering information,please contact Maxim/Dallas Direct!at 1-888-629-4642, or visit Maxim’s website at https://www.docsj.com/doc/d76066395.html,.

Typical Operating Circuit appears at end of data sheet.Selector Guide appears at end of data sheet.

Note: The MAX6412/MAX6413/MAX6414 and MAX6418/MAX6419/MAX6420 are available with factory-set V CC reset thresholds from 1.575V to 5.0V in approximately 0.1V incre-ments. Insert the desired nominal reset threshold suffix (from Table 1) into the blanks following the letters UK. There are 33standard versions with a required order increment of 2500pieces. Sample stock is generally held on standard versions only (see Standard Versions Table). Required order increment is 10,000 pieces for nonstandard versions. Contact factory for availability. All devices are available in tape-and-reel only. Devices are available in both leaded and lead-free packaging.Specify lead-free by replacing “-T” with “+T” when ordering.

M A X 6412–M A X 6420

with Capacitor-Adjustable Reset Timeout Delay

2_______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V CC = 1V to 5.5V, T A = T MIN to T MAX , unless otherwise specified. Typical values are at V CC = 5V and T A = +25°C.) (Note 1)

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.

All Voltages Referenced to GND

V CC ........................................................................-0.3V to +6.0V SRT, MR , RESET IN....................................-0.3V to (V CC + 0.3V)RESET, RESET (Push-Pull).........................-0.3V to (V CC + 0.3V)RESET (Open-Drain).............................................-0.3V to +6.0V Input Current (All Pins).....................................................±20mA Output Current (RESET , RESET)......................................±20mA

Continuous Power Dissipation (T A = +70°C)

5-Pin SOT23-5 (derate 7.1mW/°C above +70°C)........571mW Operating Temperature Range .........................-40°C to +125°C Junction Temperature......................................................+150°C Storage Temperature Range.............................-65°C to +150°C Lead Temperature (soldering, 10s).................................+300°C

MAX6412–MAX6420

with Capacitor-Adjustable Reset Timeout Delay

_______________________________________________________________________________________3

ELECTRICAL CHARACTERISTICS (continued)

(V CC = 1V to 5.5V, T A = T MIN to T MAX , unless otherwise specified. Typical values are at V CC = 5V and T A = +25°C.) (Note 1)

Typical Operating Characteristics

(V CC = 5V, C SRT = 1500pF, T A = +25°C, unless otherwise noted.)

4

3

2

1

00

3

1

2

4

5

6

SUPPLY CURRENT vs.SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

S U P P L Y C U R R E N T (μA )

01.00.5

2.01.5

3.02.5

3.5-50

25

-25

50

75

100

125

SUPPLY CURRENT vs.TEMPERATURE

TEMPERATURE (°C)

S U P P L Y C U R R E N T (μA )

0.11

100

10

1000

10,000

0.001

0.10.011101001000

RESET TIMEOUT PERIOD vs. C SRT

M A X 6412-20 t o c 03

C SRT (nF)

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

M A X 6412–M A X 6420

with Capacitor-Adjustable Reset Timeout Delay

4_______________________________________________________________________________________

4.05

4.10

4.20

4.15

4.25

4.30-50

-25

25

50

75

100

125

RESET TIMEOUT PERIOD vs. TEMPERATURE

TEMPERATURE (°C)

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

RESET TIMEOUT PERIOD vs. TEMPERATURE

200

250

350300500550450400600

R E S E T T I M E O U T P E R I O D (μs )-50

25

-25

50

75100

125

TEMPERATURE (°C)

1.250

1.2601.2551.2701.2651.2751.280-50

25

50

-25

75

100

125

RESET IN THRESHOLD VOLTAGE

vs. TEMPERATURE

M A X 6412-20 t o c 06

TEMPERATURE (°C)R E S E T I N T H R E S H O L D V O L T A G E (V

)0

502510075150125175

400

200

600

800

1000

MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE

RESET THRESHOLD OVERDRIVE (mV)

T R A N S I E N T D U R A T I O N (μs )

Typical Operating Characteristics (continued)

(V CC = 5V, C SRT = 1500pF, T A = +25°C, unless otherwise noted.)

Detailed Description

The MAX6412–MAX6420 low-power microprocessor (μP) supervisory circuits provide maximum adjustability for supply-voltage monitoring and reset functionality. In addition, the MAX6412–MAX6420 reset timeout period is adjustable using an external capacitor.

The MAX6412/MAX6413/MAX6414 have factory-trimmed reset threshold voltages in approximately 100mV increments from 1.575V to 5.0V with a manual reset input. The MAX6415/MAX6416/MAX6417 contain a reset threshold that can be adjusted to any voltage above 1.26V using external resistors. The MAX6418/MAX6419/MAX6420 offer both a factory-trimmed reset threshold and an adjustable reset threshold input for dual-voltage monitoring.

A reset signal is asserted when V CC and/or RESET IN falls below the preset values or when MR is asserted.The reset remains asserted for an externally pro-grammed interval after V CC and/or RESET IN has risen above the reset threshold or MR is deasserted.

Reset Output

The reset output is typically connected to the reset input of a μP. A μP’s reset input starts or restarts the μP

in a known state. The MAX6412–MAX6420 μP supervi-sory circuits provide the reset logic to prevent code-execution errors during power-up, power-down, and brownout conditions (see Typical Operating Circuit ). F or the MAX6413, MAX6416, and MAX6419, RESET changes from low to high whenever V CC or RESET IN drops below the reset threshold voltages. Once RESET IN and V CC exceed their respective reset threshold volt-age(s), RESET remains high for the reset timeout period,then goes low.

On power-up, once V CC reaches 1V, RESET is guaran-teed to be a logic high. For applications requiring valid reset logic when V CC is less than 1V, see the section Ensuring a Valid RESET/RESET Output Down to V CC = 0.The active-low RESET output of the remaining supervi-sors is the inverse of the MAX6413, MAX6416, and MAX6419 active-high RESET output and is guaranteed valid for V CC ≥1V.

Reset Threshold

The MAX6415–MAX6420 monitor the voltage on RESET IN with an external resistor voltage-divider (F igure 1).

MAX6412–MAX6420

with Capacitor-Adjustable Reset Timeout Delay

_______________________________________________________________________________________5

Pin Description

M A X 6412–M A X 6420

Use the following formula to calculate the externally monitored voltage (V MON_TH ):

V MON_TH = V RST ?(R1 + R2)/R2

where V MON_TH is the desired reset threshold voltage and V RST is the reset input threshold (1.26V). Resistors R1 and R2 can have very high values to minimize cur-rent consumption due to low leakage currents. Set R2to some conveniently high value (1M ?, for example)and calculate R1 based on the desired monitored volt-age, using the following formula:

R1 = R2 x (V MON_TH /V RST - 1) (?)

Manual Reset Input

(MAX6412/MAX6413/MAX6414)

Many μP based products require manual reset capabil-ity, allowing the operator, a technician, or external logic circuitry to initiate a reset. A logic low on MR asserts reset. Reset remains asserted while MR is low and for the reset timeout period after MR returns high.

The MR has an internal 20k ?pullup resistor so it can be left open if not used. Connect a normally open momentary switch from MR to ground to create a man-ual reset function (external debounce circuitry is not required for long reset timeout periods).

A manual reset option can easily be implemented with the MAX6415–MAX6420 by connecting a normally open momentary switch in parallel with R2 (Figure 2). When the switch is closed, the voltage on RESET IN goes to zero,initiating a reset. Similar to the MAX6412/MAX6413/MAX6414 manual reset, reset remains asserted while the switch is closed and for the reset timeout period after the switch is opened.

Monitoring Voltages Other than V CC

(MAX6415/MAX6416/MAX6417)

The MAX6415/MAX6416/MAX6417 contain an adjustable reset threshold input. These devices can be used to monitor voltages other than V CC . Calculate V MON_TH as shown in the Reset Threshold section. (See Figure 3.)

with Capacitor-Adjustable Reset Timeout Delay

6

_______________________________________________________________________________________

Figure 1. Calculating the Monitored Threshold Voltage (V MON_TH )

MAX6415–MAX6420

Figure 3. Monitoring External Voltages

Dual-Voltage Monitoring

(MAX6418/MAX6419/MAX6420) The MAX6418/MAX6419/MAX6420 contain both facto-ry-trimmed threshold voltages and an adjustable reset threshold input, allowing the monitoring of two voltages, V CC and V MON_TH(see F igure 4). Reset is asserted when either of the voltages falls below its respective threshold voltage.

Application Information

Selecting a Reset Capacitor The reset timeout period is adjustable to accommodate a variety of μP applications. Adjust the reset timeout period (t RP) by connecting a capacitor (C SRT) between SRT and ground. Calculate the reset timeout capacitor as follows:

C SRT= (t RP- 275μs) / (2.73 ?106)

where t RP is in seconds and C SRT is in Farads The reset delay time is set by a current/capacitor-con-trolled ramp compared to an internal 0.65V reference.

An internal 240nA ramp current source charges the external capacitor. The charge to the capacitor is cleared when a reset condition is detected. Once the

reset condition is removed, the voltage on the capacitor ramps according to the formula: dV/dt = I/C. The C SRT capacitor must ramp to 0.65V to deassert the reset.

C SRT must be a low-leakage (<10nA) type capacitor, ceramic is recommended.

Operating as a Voltage Detector

The MAX6412–MAX6420 can be operated in a voltage detector mode by floating the SRT pin. The reset delay

times for V CC rising above or falling below the threshold

are not significantly different. The reset output is deasserted smoothly without false pulses.

MAX6412–MAX6420

with Capacitor-Adjustable Reset Timeout Delay _______________________________________________________________________________________7

M A X 6412–M A X 6420

Interfacing to Other Voltages for Logic

Compatibility

The open-drain outputs of the MAX6414/MAX6417/MAX6420 can be used to interface to μPs with other logic levels. As shown in Figure 5, the open-drain out-put can be connected to voltages from 0 to 5.5V. This allows for easy logic compatibility to various micro-processors.

Negative-Going V CC Transients

In addition to issuing a reset to the μP during power-up,power-down, and brownout conditions, these supervisors are relatively immune to short-duration negative-going transients (glitches). The Maximum Transient Duration vs.Reset Threshold Overdrive graph in the Typical Operating Characteristics shows this relationship.

The area below the curve of the graph is the region in which these devices typically do not generate a reset pulse. This graph was generated using a negative-going pulse applied to V CC , starting above the actual reset threshold (V TH ) and ending below it by the magni-tude indicated (reset-threshold overdrive). As the mag-nitude of the transient decreases (farther below the reset threshold), the maximum allowable pulse width decreases. Typically, a V CC transient that goes 100mV below the reset threshold and lasts 50μs or less will not cause a reset pulse to be issued.

Ensuring a Valid RESET or RESET

Down to V CC = 0

When V CC falls below 1V, RESET /RESET current sink-ing (sourcing) capabilities decline drastically. In the case of the MAX6412, MAX6415, and MAX6418, high-impedance CMOS-logic inputs connected to RESET can drift to undetermined voltages. This presents no problems in most applications, since most μPs and other circuitry do not operate with V CC below 1V.

In those applications where RESET must be valid down to 0, adding a pulldown resistor between RESET and ground sinks any stray leakage currents, holding RESET low (Figure 6). The value of the pulldown resis-tor is not critical; 100k ?is large enough not to load RESET and small enough to pull RESET to ground. For applications using the MAX6413, MAX6416, and MAX6419, a 100k ?pullup resistor between RESET and V CC will hold RESET high when V CC falls below 1V (Figure 7). Open-drain RESET versions are not recom-mended for applications requiring valid logic for V CC down to 0.

with Capacitor-Adjustable Reset Timeout Delay

8

_______________________________________________________________________________________

Figure 5. MAX6414/MAX6417/MAX6420 Open-Drain RESET

Output Allows use with Multiple Supplies

Figure 6. Ensuring RESET Valid to V CC

= 0

Figure 7. Ensuring RESET Valid to V CC = 0

Layout Consideration

SRT is a precise current source. When developing the layout for the application, be careful to minimize board capacitance and leakage currents around this pin.Traces connected to SRT should be kept as short as possible. Traces carrying high-speed digital signals and traces with large voltage potentials should be rout-ed as far from SRT as possible. Leakage current and stray capacitance (e.g., a scope probe) at this pin could cause errors in the reset timeout period. When evaluating these parts, use clean prototype boards to ensure accurate reset periods.

RESET IN is a high-impedance input, which is typically driven by a high-impedance resistor-divider network (e.g., 1M ?to 10M ?). Minimize coupling to transient sig-nals by keeping the connections to this input short. Any DC leakage current at RESET IN (e.g., a scope probe)causes errors in the programmed reset threshold.

Chip Information

TRANSISTOR COUNT: 325PROCESS: BiCMOS

MAX6412–MAX6420

with Capacitor-Adjustable Reset Timeout Delay

_______________________________________________________________________________________9

Table 1. Reset Voltages Suffix Table

M A X 6412–M A X 6420

with Capacitor-Adjustable Reset Timeout Delay

10______________________________________________________________________________________

Contact factory for availability of nonstandard versions.

MAX6412–MAX6420

with Capacitor-Adjustable Reset Timeout Delay

______________________________________________________________________________________11

Typical Operating Circuit

M A X 6412–M A X 6420

with Capacitor-Adjustable Reset Timeout Delay

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.

12____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600?2005 Maxim Integrated Products

Printed USA

is a registered trademark of Maxim Integrated Products, Inc.

S O T -23 5L .E P

S

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,go to https://www.docsj.com/doc/d76066395.html,/packages .)

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