M48T212Y datasheet(18/32 Pages) STMICROELECTRONICS

18 / 32 page

M48T212Y, M48T212V

18/32

VCC Switch Output

Vccsw output goes low when VOUT switches to

VCC turning on a customer supplied P-Channel

MOSFET (see Figure 4., page 7). The Motorola

MTD20P06HDL is recommended. This MOSFET

in turn connects VOUT to a separate supply when

the current requirement is greater than IOUT1 (see

Table 14., page 25). This output may also be used

simply to indicate the status of the internal battery

switchover comparator, which controls the source

(VCC or battery) of the VOUT output.

Power-on Reset

The M48T212Y/V continuously monitors VCC.

When VCC falls to the power fail detect trip point,

the RST pulls low (open drain) and remains low on

power-up for trec after VCC passes VPFD (max).

The RST pin is an open drain output and an appro-

priate pull-up resistor to VCC should be chosen to

control rise time.

Note: If the RST output is fed back into either of

the RSTIN inputs (for a microprocessor with a bi-

directional reset) then a 1k

Ω (max) pull-up resistor

is recommended.

Reset Inputs (RSTIN1 & RSTIN2)

The M48T212Y/V provides two independent in-

puts which can generate an output reset. The du-

ration and function of these resets is identical to a

reset generated by a power cycle. Table 9 and Fig-

ure 10 illustrate the AC reset characteristics of this

function. During the time RST is enabled (tR1HRH

& tR2HRH), the Reset Inputs are ignored.

Note: RSTIN1 and RSTIN2 are each internally

pulled up to VCC through a 100KΩ resistor.

Figure 10. (RSTIN1 & RSTIN2) Timing Waveforms

Table 9. Reset AC Characteristics

Note: 1. Valid for Ambient Operating Temperature: TA = 0 to 70°C or –40 to 85°C; VCC = 4.5 to 5.5V or 3.0 to 3.6V (except where noted).

2. Pulse width less than 50ns will result in no RESET (for noise immunity).

3. Pulse width less than 20ms will result in no RESET (for noise immunity).

4. CL = 5pF (see Figure 14., page 24).

Symbol

Parameter(1)

Min

Max

Unit

tR1

(2)

RSTIN1 Low to RSTIN1 High

200

tR2

(3)

RSTIN2 Low to RSTIN2 High

100

tR1HRH

(4)

RSTIN1 High to RST High

200

tR2HRH

(4)

RSTIN2 High to RST High

200

AI02642

RSTIN1

RST

RSTIN2

tR1

tR1HRH

tR2

tR2HRH

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