LTC2990CMSTRPBF datasheet(13/24 Pages) LINER

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LTC2990

2990f

applicaTions inForMaTion

delivers the data byte and the LTC2990 acknowledges

once more and latches the data into its internal register.

The transmission is ended when the master sends a STOP

condition. If the master continues sending a second data

byte, as in a Write Word command, the second data byte

willbeacknowledgedbytheLTC2990andwrittentothenext

Read Protocol

ThemasterbeginsareadoperationwithaSTARTcondition

followed by the seven bit slave address and the R/W# bit

settozero.TheaddressedLTC2990acknowledgesthisand

then the master sends a command byte which indicates

which internal register the master wishes to read. The

LTC2990acknowledgesthisandthenlatchesthelowerfour

bitsofthecommandbyteintoitsinternalRegisterAddress

pointer.ThemasterthensendsarepeatedSTARTcondition

followed by the same seven bit address with the R/W# bit

now set to one. The LTC2990 acknowledges and sends

the contents of the requested register. The transmission

is ended when the master sends a STOP condition. The

byte is read. If the master acknowledges the transmitted

data byte, as in a Read Word command, the LTC2990

will send the contents of the next sequential register as

the second data byte. The byte following register 0x0F is

Control Register

The control register (Table 3) determines the selected

measurement mode of the device. The LTC2990 can be

configured to measure voltages, currents and tempera-

tures.Thesemeasurementscanbesingle-shotorrepeated

measurements. Temperatures can be set to report in

Celsius or Kelvin temperature scales. The LTC2990 can be

configured to run particular measurements, or all possible

measurementspertheconfigurationspecifiedbythemode

bits. The power-on default configuration of the control

measurement of the internal temperature sensor, when

triggered. This mode prevents the application of remote

diode test currents on pins V1 and V3, and remote diode

terminations on pins V2 and V4 at power-up.

Status Register

The status register (Table 3) reports the status of a par-

ticular conversion result. When new data is written into a

particular result register, the corresponding DATA_VALID

bit is set. When the register is addressed by the I2C inter-

face, the status bit (as well as the DATA_VALID bit in the

respectiveregister)iscleared.Thehostcanthendetermine

if the current available register data is new or stale. The

busy bit, when high, indicates a single-shot conversion is

in progress. The busy bit is always high during repeated

mode, after the initial conversion is triggered.

STOP

2990 F04

START

ADDRESS

R/W

1-7

a6-a0

b7-b0

DATA

ACK

Figure 4. Data Transfer Over I2C or SMBus

A DATA

ADDRESS

COMMAND

0 b7:b0

10011a1:a0

FROM MASTER TO SLAVE

XXXXXb3:b0

2990 F05

FROM SLAVE TO MASTER

A: ACKNOWLEDGE (LOW)

A#: NOT ACKNOWLEDGE (HIGH)

R: READ BIT (HIGH)

W#: WRITE BIT (LOW)

S: START CONDITION

P: STOP CONDITION

Figure 5. LTC2990 Serial Bus Write Byte Protocol

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