MAX6305 데이터 시트보기 (PDF) - Maxim Integrated

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MAX6305

5-Pin, Multiple-Input, Programmable Reset ICs

Maxim Integrated 

5-Pin, Multiple-Input,

Programmable Reset ICs

VCC

*

+1.23V

RST IN1

RST IN2

MR

+1.23V

RESET

GENERATOR

RESET**

RESET***

†

+1.23V

OVRST IN

+1.23V

††

VCC

MAX6305–MAX6313

†††

GND

* MAX6306/MAX6307/MAX6309/MAX6310/MAX6312/MAX6313 ONLY

** MAX6305–MAX6310 ONLY

*** MAX6311/MAX6312/MAX6313 ONLY

† MAX6307/MAX6310/MAX6313 ONLY

†† MAX6305/MAX6308/MAX6311 ONLY

††† MAX6306/MAX6309/MAX6312 ONLY

Figure 1. Functional Diagram

open-drain, N-channel output. The MAX6308/MAX6309/

MAX6310 feature an active-low, complementary output

structure that both sinks and sources current, and the

MAX6311/MAX6312/MAX6313 have an active-high com-

plementary reset output.

The MAX6305/MAX6308/MAX6311 switch from under-

voltage lockout operation to normal operation between

1.5V < VCC < 2.5V. Below 1.5V, VCC undervoltage-

lockout mode asserts RESET. Above 2.5V, VCC normal-

operation mode asserts reset if RST IN_ falls below the

RST IN_ threshold.

Manual-Reset Input

(MAX6306/MAX6309/MAX6312)

Many µP-based products require manual-reset capability,

allowing an operator or external logic circuitry to initiate a

reset. A logic low on MR asserts reset. Reset remains

asserted while MR is low, and for a reset active timeout

period (tRP) after MR returns high. This input has an inter-

nal 63.5kΩ pull-up resistor, so it can be left open if it is not

used. MR can be driven with TTL-logic levels in 5V sys-

tems, with CMOS-logic levels in 3V systems, or with open-

drain/collector output devices. Connect a normally open

momentary 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 ground provides additional noise immunity.

The MR pin has internal ESD-protection circuitry that may

be forward biased under certain conditions, drawing

excessive current. For example, assume the circuitry driv-

ing MR uses a +5V supply other than VCC. If VCC drops or

browns out lower than +4.7V, MR’s absolute maximum rat-

ing is violated (-0.3V to (VCC + 0.3V)), and undesirable

current flows through the ESD structure from MR to VCC.

To avoid this, it is recommended that the supply for the MR

pin be the same as the supply monitored by VCC. In this

way, the voltage at MR will not exceed VCC.

Adjustable Reset Inputs

The MAX6305–MAX6313 each have one or more reset

inputs (RST IN_ /OVRST IN). These inputs are com-

pared to the internal reference voltage (Figure 1).

Connect a resistor voltage divider to RST IN_ such that

VRST IN_ falls below VRSTH (1.23V) when the monitored

voltage (VIN) falls below the desired reset threshold

(VTH) (Figure 2). Calculate the desired reset voltage

with the following formula:

VTH

=

_R_1__+__R_2_

R2

x

VRSTH

6 _______________________________________________________________________________________

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