DS3050W 데이터 시트보기 (PDF) - Maxim Integrated

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DS3050W

3.3V Single-Piece 4Mb Nonvolatile SRAM with Clock

Maxim Integrated 

3.3V Single-Piece 4Mb Nonvolatile SRAM

with Clock

Detailed Description

The DS3050W is a 4Mb (512k x 8 bits) fully static, NV

memory similar in function and organization to the

DS1250W NV SRAM, but also containing an RTC and

rechargeable ML battery. The DS3050W NV SRAM con-

stantly monitors VCC for an out-of-tolerance condition.

When such a condition occurs, the lithium energy source

is automatically switched on and write protection is

unconditionally enabled to prevent data corruption. There

is no limit to the number of write cycles that can be exe-

cuted, and no additional support circuitry is required for

microprocessor interfacing. This device can be used in

place of SRAM, EEPROM, or flash components.

User access to either the SRAM or the real-time clock

registers is accomplished with a byte-wide interface

and discrete control inputs, allowing for a direct inter-

face to many 3.3V microprocessor devices.

The DS3050W RTC contains a full-function, year 2000-

compliant (Y2KC) clock/calendar with an RTC alarm,

watchdog timer, battery monitor, and power monitor.

RTC registers contain century, year, month, date, day,

hours, minutes, and seconds data in a 24-hour BCD

format. Corrections for day of the month and leap year

are made automatically.

The DS3050W RTC registers are double-buffered into

an internal and external set. The user has direct access

to the external set. Clock/calendar updates to the exter-

nal set of registers can be disabled and enabled to

allow the user to access static data. Assuming the

internal oscillator is on, the internal registers are contin-

ually updated, regardless of the state of the external

registers, assuring that accurate RTC information is

always maintained.

The DS3050W contains interrupt (IRQ/FT) and reset

(RST) outputs, which can be used to control CPU activ-

ity. The IRQ/FT interrupt output can be used to gener-

ate an external interrupt when the RTC register values

match user-programmed alarm values. The interrupt is

always available while the device is powered from the

system supply, and it can be programmed to occur

when in the battery-backed state to serve as a system

wake-up. The IRQ/FT output can also be used as a

CPU watchdog timer. CPU activity is monitored and an

interrupt can be activated if the correct activity is not

detected. The RST output can be used to detect a sys-

tem power-down or failure and hold the CPU in a safe

state until normal power returns.

The DS3050W constantly monitors the voltage of the

internal battery. The battery-low flag (BLF) in the RTC

FLAGS register is not writeable and should always be a

0 when read. Should a 1 ever be present, the battery

voltage is below ∼2V and the contents of the clock and

SRAM are questionable.

The DS3050W module is constructed on a standard 256-

ball, 27mm x 27mm BGA substrate. Unlike other sur-

face-mount NV memory modules that require the battery

to be removable for soldering, the internal ML battery

can tolerate exposure to convection reflow soldering

temperatures, allowing this single-piece component to

be handled with standard BGA assembly techniques.

Table 1. RTC/Memory Operational Truth Table

CS

WE

CE

OE

0

1

1

0

0

1

1

1

0

0

1

X

1

1

0

0

1

1

0

1

1

0

0

X

1

X

1

X

0

X

0

X

X = Don’t care. (1) = See Figure 4.

MODE

RTC Read

RTC Read

RTC Write

SRAM Read

SRAM Read

SRAM Write

Standby

Invalid (1)

ICC

Active

Active

Active

Active

Active

Active

Standby

Active

OUTPUTS

Active

High Impedance

High Impedance

Active

High Impedance

High Impedance

High Impedance

Invalid

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