L99LD20 datasheet(39/61 Pages) STMICROELECTRONICS

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DS11366 Rev 3

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L99LD20

SPI functional description

Table 26. Testing procedure description

Step

Description

Action

SPI Frames (binary, unless

otherwise specified)

Blank Check

(load)

In this step, antifuses are compared

with a higher resistance than the

standard one - to be sure they are

initially unburned. Their content is

loaded into bits (20÷13) of CTM

Send an SPI write to

CTM

00 111110 011

000000000000000000000

Blank Check

(read)

During previous step, the result of

Blank Check Read is loaded into bits

(20÷13) of CTM register. A read

operation is required this result.

Send an SPI read for

customer trimming

the SDO frame

received from device

01 111110 000

000000000000000000001

Blank Check

(decision)

A decision must be taken, based on

the previous result. If antifuses were

damaged, device must be discarded,

otherwise the flow can proceed.

If the answer to

previous SPI read is

different from

xx0000xx, then

device must be

discarded

Select bits to

write

Desired setting for default values of

some control bits must be chosen.

Let's assume that the chosen 8 bit

word is: ctm, corresponding to the 8

bits of CTM from 20 to 13

(DEF_HLEDCUR + DEF_DAC1 +

DEF_VLEDTOFF1 + DEF_MS +

DEF_BSTDIS).

Select 8 bit word to

write (ctmd)

Burn (X3)

In this step, selected word (i.e. ctmd)

must be written in the OTPs. This step

must be repeated three times.

It it recommended to wait the

completion of a burn operation before

starting the following one. Time

required to burn one word depends on

the number of fuses to be burned and

it is equal to: 2.85 µs + 401 µs *

Prepare the right

external setup (see

Table 27, "Writing test

conditions").

Send an SPI write to

CTM. Selected word

must be placed in bits

(20÷13) of CTM.

Last bit depends on

odd parity check.

00 111110 100

[ctmd]000000000000x

End Of

Trimming

(X3)

In this step, end of trimming antifuse is

burned. This step must be repeated

three times.

It it recommended to wait the

completion of a burn operation before

starting the following one. Time

required to burn one bit is almost equal

to: 404µs

Send an SPI write to

CTM

00 111110 111

000000000000000000001

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