935271416518 [NXP]

IC 2-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8, 3.90 MM, PLASTIC, MS-012, SO-8, Power Management Circuit;


型号：	935271416518
厂家：	NXP
描述：	IC 2-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8, 3.90 MM, PLASTIC, MS-012, SO-8, Power Management Circuit 光电二极管
文件：	总12页 (文件大小：116K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

INTEGRATED CIRCUITS

MAX708R/S/T

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

Product data

2003 Feb 13

Supersedes data of 20 Jun 2002

Philips

Semiconductors

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

DESCRIPTION

The MAX708R/S/T are microprocessor supervisory circuits used to

monitor +3 V power supply levels in +3 V to +5 V microprocessor

and other logic systems. The R, S, T suffixes have reset thresholds

of 2.63 V, 2.93 V and 3.08 V, respectively. They reduce the number

of circuit components, and improve reliability and accuracy

compared to using separate ICs or discrete components.

The MAX708R/S/T features make the MAX708R/S/T ideal for use in

portable, battery operated equipment. The low supply current,

typically 50 µA, minimizes battery load. Both RESET and RESET

are active during power-up, power-down and brownout conditions

An active-LOW manual reset input is also available.

A 1.25 V threshold detector provides power-fail warning. This

independent comparator can be used to monitor a second voltage

supply and provide an early warning to the microprocessor that

voltage is falling. This allows for an orderly shutdown, transmitting

an alert to an operator, or activation of an alternate power source

before the device asserts the reset signals.

The device is available in the 8-pin SO package.

FEATURES

APPLICATIONS

• RESET and RESET signals

• Battery powered devices

• Critical microprocessor monitoring

• Controllers

• Independent comparator with 1.25 V threshold for power failure or

low battery warning

• Manual reset input

• Portable instruments

• 50 µA quiescent current

• Reset thresholds of 2.63, 2.93, and 3.08 V

• Guaranteed RESET assertion to V = 1 V

SIMPLIFIED SYSTEM DIAGRAM

REGULATED

DC SUPPLY (V

)

UNREGULATED

DC SUPPLY

MICROPROCESSOR

RESET

RESET INPUT

INTERRUPT

MAX708

PFO

PFI

PUSH-BUTTON

SWITCH

GND

SL01640

Figure 1. Simplified system diagram.

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

ORDERING INFORMATION

PACKAGE

TEMPERATURE

RANGE

TYPE NUMBER

NAME

DESCRIPTION

MAX708xD

SO8

plastic small outline package; 8 leads (see dimensional drawing)

–45 °C to +85 °C

NOTE:

The device has 3 voltage output options, indicated by the ‘x’ on the

‘Type number’.

Part number

MAX708RD

MAX708SD

MAX708TD

Threshold Voltage (Typical)

2.63 V

2.93 V

3.08 V

PIN CONFIGURATION

PIN DESCRIPTION

PIN SYMBOL

DESCRIPTION

TOP VIEW

Manual reset input (Active-LOW). Triggers a

reset pulse when pulled below 0.6 V. Connect

RESET

to V or leave floating if not used.

SO8

Supply voltage input.

Ground.

GND

PFI

PFO

Power fail comparator input. When PFI is less

than 1.25 V, PFO goes LOW, otherwise PFO

remains HIGH. Connect to ground if not used.

SL01639

Figure 2. Pin configuration.

PFO

Power fail comparator output (Active-LOW).

When voltage at PFI is less than 1.25 V, PFO

goes LOW and sinks current. Do not connect

if not used.

No connection.

RESET

Active-LOW reset output. RESET is LOW if

is below the threshold voltage or if MR is

held LOW. RESET is maintained for 200 ms

after the reset conditions are terminated.

RESET

Active-HIGH reset output. RESET is HIGH if

is below the threshold voltage or if MR is

held LOW. RESET is maintained for 200 ms

after the reset conditions are terminated.

MAXIMUM RATINGS

SYMBOL

PARAMETER

Supply voltage

Other input pin voltage

CONDITIONS

MIN.

–0.3

–

MAX.

UNIT

6.0

Note 1

+ 0.3

Input current at V or GND

V/µs

°C

Output current, all outputs

–

100

+85

+160

470

Rate of rise at V

–

amb

Ambient temperature

–40

–65

–

stg

Storage temperature

°C

Power dissipation, SO8 package

= 70 °C; Note 2

amb

NOTES:

1. Input voltage limits on PFI and MR can be exceeded provided the input current is less than 10 mA.

2. Derate the dissipation 5.88 mW/°C above 70 °C.

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

ELECTRICAL CHARACTERISTICS

amb

= –40 °C to +85 °C; V = (V + 0.7 V) to 5.5 V, unless otherwise specified.

RST(max)

SYMBOL

PARAMETER

Operating voltage range

Supply current

CONDITIONS

MIN.

1.2

–

TYP.

–

MAX.

5.5

300

500

2.70

3.00

3.15

–

UNIT

< 3.6 V

< 5.5 V

µA

SUP

–

MAX708R

MAX708S

MAX708T

2.55

2.85

3.00

–

2.63

2.93

3.08

RST

Reset threshold (Note 1)

Reset threshold hysteresis

Reset delay time (Note 1)

MAX708R; V = 3.0 V

140

–

200

–

280

–

RST

MAX708S, MAX708T; V = 3.3 V

MAX708R, MAX708S, MAX708T; V = 5.0 V

< V < 3.6V;

× 0.8

–

HIGH-level output voltage

RESET

PFO

RST(max)

= 500 µA

SOURCE

4.5 V < V < 5.5 V;

– 1.5

× 0.8

– 1.5

× 0.8

– 1.5

–

= 800 µA

SOURCE

< V < 3.6V;

RST(max)

= 500 µA

SOURCE

4.5 V < V < 5.5 V;

–

= 800 µA

SOURCE

< V < 3.6V;

–

RST(max)

= 500 µA

SOURCE

4.5 V < V < 5.5 V;

–

= 800 µA

SOURCE

< V < 3.6 V;

–

0.3

0.4

LOW-level output voltage

RESET

RST(max)

= 1.2 mA

SINK

4.5 V < V < 5.5 V;

–

= 3.2 mA

SINK

= 1.2 V; I

= 100 µA

SINK

–

0.3

< V < 3.6 V;

RESET

PFO

RST(max)

= 500 µA

SINK

4.5 V < V < 5.5 V;

–

0.4

0.3

0.4

= 1.2 mA

SINK

< V < 3.6 V;

RST(max)

= 1.2 mA

SINK

4.5 V < V < 5.5 V;

= 3.2 mA

SINK

< V < 3.6 V; MR = 0 V

100

500

150

–

250

–

250

600

–

µA

MR pull-up current

RST(max)

4.5 V < V < 5.5 V; MR = 0 V

< V < 3.6 V

MR pulse width

RST(max)

4.5 V < V < 5.5 V

–

< V < 3.6 V

–

0.6

0.8

–

MR LOW-level input threshold

MR HIGH-level input threshold

MR to reset out delay (Note 1)

RST(max)

4.5 V < V < 5.5 V

–

< V < 3.6 V

× 0.7

–

RST(max)

4.5 V < V < 5.5 V

2.0

–

< V < 3.6 V

–

750

250

1.3

RST(max)

4.5 V < V < 5.5 V

–

PFI input threshold

PFI input current

PFI falling; MAX708R: V = 3.0 V;

MAX708S/T: V = 3.3 V

1.2

1.25

–25

0.01

+25

NOTE:

1. Applies to RESET and RESET.

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

TIMING DIAGRAM

On power-up, when V reaches 1 V, RESET is guaranteed to be a

Event F: The V rises above the reset threshold again and

logic LOW and RESET is guaranteed to be a logic HIGH.

remains above the reset threshold for typically 200 ms. At G, the

reset is once again released.

Event A: V rises to the reset threshold voltage, V

. At this time,

RST

the internal reset delay timer is initiated. RESET and RESET will

remain asserted for the reset delay time, t of typically 200 ms

Event H: The MR is externally pulled LOW for longer than 150 ns

(minimum MR pulse width, t

for V = +5 V).

RST

after the supply voltage rises above the reset threshold, V

RST

Event I: The manual reset is asserted within 250 ns (maximum MR

to reset out delay time, t for V = +5V).

Event B: At this time, the resets are released. RESET goes HIGH;

while RESET goes LOW. The reset delay time helps to ensure valid

reset signals despite erratic changes in supply voltage.

Event J: the MR pin returns HIGH. At this point, reset delay timer is

initiated and in typically 200 ms, (at Event K), the reset condition is

released.

Events C–E: At Event C, under brown-out conditions, V falls

below the reset threshold minus the hysteresis voltage (typically

20 mV), and the reset signal is asserted. As power recovers and

Event L: On power-down, when V falls below V

RESET and RESET are guaranteed to be asserted until V falls

below 1 V.

– 20 mV,

RST

rises above the reset threshold (Event D), it once again

initiates the reset delay time. At Event E, V falls below the reset

threshold before the reset delay time has elapsed and reset remains

asserted.

– 20 mV

RST

RESET

TIME

SL01812

Figure 3. Timing diagram.

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

TECHNICAL DISCUSSION

General discussion

RESET and RESET outputs

The MAX708R/S/T microprocessor supervisor circuits are

comprised of both RESET and RESET outputs, a MR manual reset

input, and a comparator which may be used for power-failure

detection (see Figure 4).

The MAX708R/S/T RESET and RESET outputs are push-pull

outputs and do not require an external pull-up resistor. The RESET

output is active-LOW logic, while the RESET output is active-HIGH

logic.

The reset threshold voltages are guaranteed within ±3% of the

nominal reset threshold. The MAX708R/S/T are designed to monitor

+3 V to +3.3 V power supplies in +3 V to +5 V microprocessor and

other logic systems. With a threshold voltage range between 5% to

10% of the nominal supply voltage, the MAX708R/S/T will assert an

output within predictable range of power supply voltage.

Manual Reset

The manual reset input, MR is active-LOW logic. It allows the

RESET and RESET to be asserted by a pushbutton switch. A

mechanical pushbutton switch is effectively debounced by the

140 ms minimum reset time delay. MR may be driven from an

external logic circuit because it is TTL/CMOS compatible. The

minimum MR input pulse is 500 ns for V = +3 V and 150 ns for

= +5 V. If manual reset will not be used, leave the pin left

floating or tie it to V

MAX708R/S/T

Power-fail comparator

The power-fail comparator has many useful purposes, such as

monitoring upstream or secondary power supplies. The Power-Fail

Output (PFO) and the non-inverting Power-Fail Input (PFI) are

pinned out. The inverting input of the power-fail comparator is

internally connected to a 1.25 V reference. The comparator has

10 mV of hysteresis which prevents repeated triggering of the

output (PFO).

RESET

GENERATOR

RST

GND

PFI

PFO

+1.25 V

POWER-FAIL

COMPARATOR

SL01813

Figure 4. MAX708R/S/T internal block diagram.

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

APPLICATION INFORMATION

Operating with a +3 V or +5 V supply

Adding hysteresis to the power-fail comparator

When powered from either +3.0 V or +5.0 V, the MAX708R/S/T

provides voltage monitoring at the reset threshold. The

MAX708R/S/T are ideal for portable applications that are powered

from a +3 V battery or an AC-DC wall adapter that generates +5 V.

Hysteresis adds noise margin to the power-fail comparator and

prevents repeated triggering of PFO when V is varying around the

comparator trip point. In Figure 5, “Adding hysteresis to the

power-fail comparator”, R1 and R2 are the divider resistors that set

the desired trip point. R3 is added from the comparator input to the

output to increase hysteresis; it is typically an order of magnitude

greater than R1 and R2. The current through R1 and R2 should be

at least 1 mA to ensure that the 25 nA max PFI input current does

significantly shift the trip point. Capacitor C1 provides noise

rejection.

Power-fail comparator

An early warning power-fail circuit uses the power-fail input to

monitor the upstream, unregulated DC supply that powers the

+3 V/+3.3 V regulator powering the MAX708R/S/T.

Figure 1, “Simplified system diagram”, shows the resistor divider

network that is connected to PFI. The network resistors R1 and R2

are chosen so that the voltage at PFI will fall below 1.25 V before

the regulator voltage drops out. The PFO signal may be used to

interrupt the microprocessor so it can perform an orderly shutdown.

CC2

Any unregulated or regulated supply can be monitored by adjusting

the resistive divider for the desired power supply trip voltage. Table 1

shows examples for nominal trip voltages of 3.7 V and 10.9 V. The

PFI

desired trip voltage, V is calculated by the following equation:

MAX708R/S/T

(R1 ) R2)

PFO

_{+ 1.25 V}ƪ

V_T

GND

Table 1. Power-fail detection circuit of

3.7 V and 10.9 V

MICROPROCESSOR

SL01814

R1 1%

R2 1%

Figure 5. Adding hysteresis to the power-fail comparator.

5 V

1 MΩ

510 kΩ

3.7 V

unregulated

power supply

PFO

12 V

1 MΩ

130 kΩ

10.9 V

CC2

unregulated

power supply

0 V

(R1 ) R2)

_{+ 1.25 V}ƪ

V_T

The hysteresis of V and V voltages are calculated by:

(R3 ) R2)

(R2 R3)

_{+ 1.25 V 1 )}ƪ

ƫ _R1

V_H

1.25 * V_CC

1.25

ǒ Ǔ₎

V_L+ 1.25 V ) R1

ǒ Ǔ

Thus,

R1 V_CC2

V_HYS+ V_H* V_L

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

Monitoring a negative voltage

The power-fail comparator can be used to monitor a negative

voltage using the circuit shown in Figure 6.

Ensuring a valid reset down to V = 0 V

When V falls below 1 V, the MAX708R/S/T RESET no longer

sinks current (i.e., it becomes open circuit). A high impedance

CMOS logic input connected to RESET can drift to undetermined

voltages. In most applications in which the microprocessor circuitry

is inoperative below 1 V this will not present a problem. However, in

applications in which RESET must be valid down to 0 V, use a

relatively large pull-down resistor from RESET to ground (Figure 7).

100 kΩ is small enough to provide a path for any stray leakage

currents to flow to ground (holding RESET LOW), while it is large

enough not to load RESET.

When the negative supply is operating in tolerance, PFO is LOW.

However, when the negative supply drops (goes positive) PFO goes

HIGH.

+3 V to +3.3 V

PFI

MAX708R/S/T

PFO

GND

TO µP

INTERRUPT

RESET

100 kΩ

MAX708R/S/T

MICROPROCESSOR

GND

V–

SL01815

GND

Figure 6. Circuit for monitoring a negative voltage.

SL01816

When monitoring a negative supply, the trip voltage, V is a

negative voltage. Use the following ratio to determine the divider

resistors:

Figure 7. RESET valid to V = Ground circuit.

Interfacing to a microprocessor with bi-directional

reset pins

V_CC* 1.25

1.25 * V_T

Microprocessors with bi-directional reset pins, such as the Motorola

68HC11 series, can be connected to the MAX708R/S/T RESET

output. The bi-directional reset of the microprocessor functions both

as a driven reset input and as an active reset driver.

Solving for V :

_{+ 1.25 *}ǒ Ǔ

V_T

V_CC* 1.25

To ensure a correct output on the MAX708R/S/T even when the

microprocessor reset pin is in the opposite state, connect a 4.7 kΩ

resistor between the reset pins as shown in Figure 8. This allows the

microprocessor to issue commands to the system regardless of the

state of the RESET pin.

PFO

+3 V

+3.3 V

0 V

4.7 kΩ

RESET

MAX708R/S/T

MOTOROLA

68HCXX

GND

SL01817

Figure 8. Interfacing to a microprocessor with bi-directional

Reset I/O

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

PACKING METHOD

The MAX708R/S/T are packed in reels, as shown in Figure 9.

GUARD

BAND

TAPE

TAPE DETAIL

REEL

ASSEMBLY

COVER TAPE

CARRIER TAPE

BARCODE

LABEL

BOX

SL01305

Figure 9. Tape and reel packing method.

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

SO8: plastic small outline package; 8 leads; body width 3.9 mm

pin 1 index

4.95

4.80

0.51

0.33

4.95

4.80

1.27

0.38

0.076

0.003

1.73

0.189

0.195

0.013

0.020

0.050

0.015

0.068

SO8

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

REVISION HISTORY

Rev

Date

Description

20030213

Product data (9397 750 10514); ECN 853–2354 29010 of 02 October 2002;

supersedes data of 20 Jun 2002 (9397 750 10023).

Modifications:

• Ordering information: change temperature range from: (0 °C to +70 °C) to: (–45 °C to +85 °C).

• Maximum ratings: change (T , operating temperature) to (T , ambient temperature).

opr

amb

20020620

Product data (9397 750 10023).

Engineering Change Notice 853–2354 28505 (date: 20020620).

2002 Feb 13

Philips Semiconductors

Product data

3 V microprocessor supervisor circuit with

power fail comparator and manual reset

MAX708R/S/T

Data sheet status

Product

status

Definitions

[1]

Level

Data sheet status

[2] [3]

Objective data

Development

This data sheet contains data from the objective specification for product development.

Philips Semiconductors reserves the right to change the specification in any manner without notice.

Preliminary data

Product data

Qualification

Production

This data sheet contains data from the preliminary specification. Supplementary data will be published

at a later date. Philips Semiconductors reserves the right to change the specification without notice, in

order to improve the design and supply the best possible product.

III

This data sheet contains data from the product specification. Philips Semiconductors reserves the

right to make changes at any time in order to improve the design, manufacturing and supply. Relevant

changes will be communicated via a Customer Product/Process Change Notification (CPCN).

[1] Please consult the most recently issued data sheet before initiating or completing a design.

[2] The product status of the device(s) described in this data sheet may have changed since this data sheet was published. The latest information is available on the Internet at URL

http://www.semiconductors.philips.com.

[3] For data sheets describing multiple type numbers, the highest-level product status determines the data sheet status.

Definitions

Short-form specification — The data in a short-form specification is extracted from a full data sheet with the same type number and title. For detailed information see

the relevant data sheet or data handbook.

Limitingvaluesdefinition— Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 60134). Stress above one or more of the limiting

values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or at any other conditions above those given

in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended periods may affect device reliability.

Application information — Applications that are described herein for any of these products are for illustrative purposes only. Philips Semiconductors make no

representation or warranty that such applications will be suitable for the specified use without further testing or modification.

Disclaimers

Life support — These products are not designed for use in life support appliances, devices, or systems where malfunction of these products can reasonably be

expected to result in personal injury. Philips Semiconductors customers using or selling these products for use in such applications do so at their own risk and agree

to fully indemnify Philips Semiconductors for any damages resulting from such application.

Right to make changes — Philips Semiconductors reserves the right to make changes in the products—including circuits, standard cells, and/or software—described

or contained herein in order to improve design and/or performance. When the product is in full production (status ‘Production’), relevant changes will be communicated

viaaCustomerProduct/ProcessChangeNotification(CPCN).PhilipsSemiconductorsassumesnoresponsibilityorliabilityfortheuseofanyoftheseproducts,conveys

nolicenseortitleunderanypatent, copyright, ormaskworkrighttotheseproducts, andmakesnorepresentationsorwarrantiesthattheseproductsarefreefrompatent,

Koninklijke Philips Electronics N.V. 2002

Contact information

For additional information please visit

http://www.semiconductors.philips.com.

Fax: +31 40 27 24825

Date of release: 02-03

9397 750 10514

For sales offices addresses send e-mail to:

sales.addresses@www.semiconductors.philips.com.

Document order number:

Philips

Semiconductors

2002 Feb 13

935271416518 [NXP]

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