MAX6351 データシートの表示（PDF） - Maxim Integrated

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MAX6351

Dual/Triple-Voltage µP Supervisory Circuits

Maxim Integrated 

Dual/Triple-Voltage

µP Supervisory Circuits

Detailed Description

Supply Voltages

The MAX6351–MAX6360 microprocessor (µP) superviso-

ry circuits maintain system integrity by alerting the µP to

fault conditions. These ICs monitor multiple-supply sys-

tems. The output reset state is guaranteed to remain

viable while either VCC1 or VCC2 is above +1V.

Threshold Levels

All the possible input voltage threshold level combina-

tions are indicated by a two-letter code in the Voltage

Threshold Levels table.

(5) 6 VCC1

3

MR

GLITCH

FILTER

VTH1

4 VCC2

VTH2

(5) (RSTIN)

RST (1)

RESET

RST2 (5)

GENERATOR

RST1 (1)

1.22V

Reset Outputs

The MAX6351 provides two active-low, push-pull reset

outputs, one corresponding to each of its two moni-

tored voltages. The MAX6353/MAX6356/MAX6359 have

an active-low, push-pull reset output that is referenced

to VCC1. The MAX6354/MAX6357/MAX6360 have an

active-low, push-pull reset output that is referenced to

VCC2. The MAX6352/MAX6355/MAX6358 provide an

active-low open-drain reset. The reset outputs are

maintained as long as at least one of the supplies is

above +1V.

Negative-Going VCC Transients

The MAX6351–MAX6360 are designed to ignore short

negative-going VCC1 and VCC2 transients. See the

Maximum VCC Transient Duration vs. Reset Threshold

Overdrive graph in the Typical Operating Characteristics.

Third Input Voltage

(MAX6355/MAX6356/MAX6357)

The MAX6355/MAX6356/MAX6357 provide an addition-

al input to monitor a third voltage. The threshold voltage

at RSTIN is typically 1.22V. To monitor a voltage higher

than 1.22V, connect a resistive divider to the circuit as

shown in Figure 2. The threshold at VEXT is:

VEXT_TH

=

1.22V





R1

+

R2

R2





Note that RSTIN is powered by VCC1, and its voltage

must therefore remain lower than or equal to VCC1.

Watchdog Input

(MAX6358/MAX6359/MAX6360)

The MAX6358/MAX6359/MAX6360 include a dual-

mode watchdog timer to monitor µP activity. The flexi-

ble timeout architecture provides a startup mode,

allowing complicated systems to complete lengthy

boots, and a normal mode, allowing the supervisor to

provide quick alerts when processor activity fails.

(5) (WDI)

WATCHDOG

TIMER

2

GND

MAX6351–MAX6360

NOTE: PIN 1 IS RST1 FOR THE MAX6351 AND RST FOR THE

MAX6352–MAX6360. PIN 5 IS RST2 FOR THE MAX6351, RSTIN

FOR THE MAX6355/MAX6356/MAX6357, WDI FOR THE MAX6358/

MAX6359/MAX6360, AND VCC1 FOR THE MAX6352/MAX6353/MAX6354.

Figure 1. Functional Diagram

VEXT

MAX6355

R1

MAX6356

MAX6357

RSTIN

R2

VCC1 ≥ VRSTIN

Figure 2. Monitoring a Third Voltage

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