MAX6709 Просмотр технического описания (PDF) - Maxim Integrated

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MAX6709

Low-Voltage, High-Accuracy, Quad Voltage Monitors in µMAX Package

Maxim Integrated 

Low-Voltage, High-Accuracy, Quad Voltage

Monitors in µMAX Package

Or, solved in terms of R1:

R1 = R2 ((VINTH / 0.62V) - 1)

VINTH

R1

R2

VREF = 0.62V

( ) R1 = R2 0V.I6N2TVH- 1

Figure 7. Setting the Auxiliary Monitor

Unused Inputs

The unused inputs (except the adjustable) are internally

connected to ground through the lower resistors of the

threshold-setting resistor pairs. The adjustable input,

however, must be connected to ground if unused.

Reset Output

The MAX6714 RESET output asserts low when VCC

drops below its specified threshold or MR asserts low

and remains low for the reset timeout period (140ms

min) after VCC exceeds its threshold and MR deasserts

(Figure 8). The output is open drain with a weak (10µA)

internal pullup to VCC. For many applications, no exter-

nal pullup resistor is required to interface with other

logic devices. An external pullup resistor to any voltage

from 0 to 5.5V overdrives the internal pullup if interfac-

ing to different logic supply voltages (Figure 9). Internal

circuitry prevents reverse current flow from the external

pullup voltage to VCC.

Manual Reset Input

Many µP-based products require manual reset capabili-

ty, allowing the operator, a test technician, or external

logic circuitry to initiate a reset. A logic low on MR

asserts RESET low. RESET remains asserted while MR is

low, and during the reset timeout period (140ms min)

after MR returns high. The MR input has an internal 20kΩ

pullup resistor to VCC, so it can be left open if unused.

Drive MR with TTL or CMOS-logic levels, or with open-

drain/collector outputs. Connect a normally open momen-

tary switch from MR to GND to create a manual reset

function; external debounce circuitry is not required. If

MR is driven from long cables or if the device is used in a

noisy environment, connecting a 0.1µF capacitor from

MR to GND provides additional noise immunity.

Reseting the µP from a 2nd Voltage

(MAX6714)

The MAX6714 can be configured to assert a reset from a

second voltage by connecting the power-fail output to

manual reset. As the VPFI_ falls below its threshold, PFO

goes low and asserts the reset output for the reset time-

out period after the manual reset input is deasserted.

(See Typical Operating Circuit.)

Power-Supply Bypassing and Grounding

The MAX6709/MAX6714 operate from a single 2.0V to

5.5V supply. In noisy applications, bypass VCC with a

0.1µF capacitor as close to VCC as possible.

VCC

VTH_

VTH_

RESET

10%

tRD

90%

tRP

Figure 8. RESET Output Timing Diagram

VCC = 3.3V

VCC

RESET

5V

100kΩ

VCC

RESET

MAX6714

GND

GND

Figure 9. Interfacing to Different Logic Supply Voltage

10 ______________________________________________________________________________________

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