M41ST87W_11 datasheet(25/54 Pages) STMICROELECTRONICS

Part #	M41ST87W

Description	5.0 V and 3.3/3.0 V secure serial RTC and NVRAM supervisor with tamper detection and 128 bytes of clearable NVRAM

PDF	54 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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25 / 54 page

M41ST87Y, M41ST87W

Operating modes

Doc ID 9497 Rev 10

25/54

Table 5.

Tamper detect timing

Figure 20.

RAM clear hardware hookup (SOX28 package only)

Most inverting charge pumps drive OUT to ground when device shut down is enabled (SHDN = logic low). Therefore, an n-

channel enhancement mode MOSFET should be used to isolate the OUT pin from the VOUT of the M41ST87.

In order to avoid turning on an on-chip parasitic diode when driving VOUT negative, a p-channel enhancement mode

MOSFET should be used to isolate the VOUT pin from the negative voltage generated by the inverting charge pump.

Symbol

Parameter

CLRPW

Min

Typ

Max

Unit

tCLRD

(1)

With input capacitance = 70 pF and resistance = 50

Ω.

Tamper RAM clear ext delay

1.0(2)

If the OF bit is set, tCLRD(min) = 0.5 ms.

1.5

2.0

tCLR

Tamper clear timing

AI07804

VCC

PFO1

SCL

M41ST87Y/W

WDI

RSTIN1

RSTIN2

PFI1

PFI2

VSS

VBAT

F32k

IRQ/OUT

SQW/FT

RST

VOUT

ECON

SDA

CAP+ CAP–

Inverting

Charge

Pump

SHDN

OUT

TP1IN

TPCLR

TP2IN

Pushbutton

Reset

PFO2

Low-Power

SRAM

VCC

Negative Output

(–1 x VIN)

To RST

To LED Display

(2)

(1)

To NMI

To INT

To 32kHz

Inhibit

Regulator

VCC

VIN

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