LTM2886 datasheet(23/38 Pages) AD

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LTM2886

Rev C

For more information www.analog.com/LTM2886

APPLICATIONS INFORMATION

Table 3. Unidirectional SPI Timing Event Description

TIME

CPHA

EVENT DESCRIPTION

0, 1

Asynchronous chip select, may be synchronous to SDI but may not lag by more than 3ns

t0 to t1

0, 1

Propagation delay chip select, logic to isolated side

Start of data transmission, data set-up

Start of transmission, data and clock set-up. Data transition must be within –13ns to 3ns of clock edge

t2 to t3

Propagation delay of data, logic side to isolated side

Propagation delay of data and clock, logic side to isolated side

0, 1

Logic side data sample time, half clock period delay from data set-up transition

t3 to t5

0, 1

Clock propagation delay, clock and data transition

t4 to t5

0, 1

Data to clock delay, must be ≤13ns

t5 to t6

0, 1

Clock to data delay, must be ≤3ns

t5 to t7

0, 1

Data and clock propagation delay

Last clock and data transition

Last clock transition

t8 to t9

Clock and data propagation delay

Clock propagation delay

t9 to t10

Data propagation delay

t11

0, 1

Asynchronous chip select transition, end of transmission

t12

0, 1

Chip select transition isolated side

Figure 11. Isolated SDA2 Pin Schematic

Figure 10. I2C Timing Diagram

2886 F11

SDA2

1.8mA

FROM

LOGIC

SIDE

LOGIC

SIDE

GLITCH FILTER

2886 F10

SDA

SDA2

SCL

SCL2

START

tPROP

tSU;DAT

tHD;DAT

tSU;ACK

SLAVE ACK

STOP

Additional proprietary circuitry monitors the slew rate on

the SDA and SDA2 signals to manage directional control

across the isolation barrier. Slew rates on both pins must

be greater than 1V/µs for proper operation.

The logic side bidirectional serial data pin, SDA, requires a

pull-up resistor or current source connected to VL. Follow

the requirements in Figures 12 and 13 for the appropri-

ate pull-up resistor on SDA that satisfies the desired rise

time specifications and VOL maximum limits for FAST and

STANDARD modes. The resistance curves represent the

maximum resistance boundary; any value may be used

to the left of the appropriate curve.

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