X5083P datasheet(3/21 Pages) XICOR

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X5083

Characteristics subject to change without notice.

3 of 21

REV 1.1.6 6/25/02

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PRINCIPLES OF OPERATION

Power On Reset

Application of power to the X5083 activates a power on

reset circuit. This circuit goes LOW at 1V and pulls the

RESET pin active. This signal prevents the system

microprocessor from starting to operate with insufﬁ-

cient voltage or prior to stabilization of the oscillator.

RESET active also blocks communication to the device

through the SPI interface. When VCC exceeds the

device VTRIP value for 200ms (nominal) the circuit

releases RESET, allowing the processor to begin exe-

cuting code. While VCC < VTRIP communications to the

device are inhibited.

Low Voltage Monitoring

During operation, the X5083 monitors the VCC level

and asserts RESET if supply voltage falls below a pre-

set minimum VTRIP. The RESET signal prevents the

microprocessor from operating in a power fail or

brownout condition and terminates any SPI communi-

cation in progress. The RESET signal remains active

until the voltage drops below 1V. It also remains active

until VCC returns and exceeds VTRIP for 200ms.

When VCC falls below VTRIP, any communications in

progress are terminated and communications are

inhibited until VCC exceeds VTRIP for tPURST.

Watchdog Timer

The watchdog timer circuit monitors the microprocessor

activity by monitoring the WDI input. The microprocessor

must toggle the CS/WDI pin periodically to prevent a

RESET signal. The CS/WDI pin must be toggled from

HIGH to LOW prior to the expiration of the watchdog time

out period. The state of two nonvolatile control bits in the

status register determine the watchdog timer period. The

microprocessor can change these watchdog bits with no

action taken by the microprocessor these bits remain

unchanged, even after total power failure.

VCC Threshold Reset Procedure

The X5083 is shipped with a standard VCC threshold

(VTRIP) voltage. This value will not change over normal

operating and storage conditions. However, in applica-

tions where the standard VTRIP is not exactly right, or if

higher precision is needed in the VTRIP value, the

X5083 threshold may be adjusted. The procedure is

described below, and uses the application of a high

voltage control signal.

Setting the VTRIP Voltage

This procedure is used to set the VTRIP to a higher

voltage value. For example, if the current VTRIP is 4.4V

and the new VTRIP is 4.6V, this procedure will directly

make the change. If the new setting is to be lower than

the current setting, then it is necessary to reset the trip

point before setting the new value.

To set the new VTRIP voltage, apply the desired VTRIP

threshold voltage to the VCC pin and tie the WP pin to

the programming voltage VP. Then send a WREN com-

mand, followed by a write of Data 00h to address 01h.

CS going HIGH on the write operation initiates the

VTRIP programming sequence. Bring WP LOW to com-

plete the operation.

Note: This operation also writes 00h to array address

01h.

Figure 1. Set VTRIP Level Sequence (VCC = desired VTRIP value)

012 345 67

SCK

06h

012 345 67 89 10

20 21 22 23

16 Bits

0001h

02h

VP = 15-18V

00h

WREN

Write

Address

Data

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