LTC2970CUFD datasheet(14/36 Pages) LINER

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LTC2970/LTC2970-1

29701fc

OPERATIO

The two bus lines, SDA and SCL, must be high when the

bus is not in use. External pull-up resistors or current

sources are required on these lines.

The LTC2970 I2C interface is SMBus compatible; it meets

all SMBus setup times, hold times and timeout require-

ments.

The LTC2970 is a receive-only (slave) device. The LTC2970

can signal the host through the SMBALERT protocol that it

wants to talk by asserting ALERT low. The LTC2970 sup-

ports the three I2C protocols summarized in Table 1.

Slave Address

The LTC2970 can respond to one of nine 7-bit addresses.

The two slave address select pins (ASEL1 and ASEL0) are

programmed by the user and determine the slave address,

as shown in Table 2.

The LTC2970 also supports the ARA address and a global

address that allows multiple LTC2970s to be programmed

with the same data simultaneously, as shown in Table 3.

Table 1. Supported I2C Command Types

READ DATA WORD:

S:ADR:W:A:CMD:A:Sr:ADR:R:A:DATA:A:DATA:NACK:P

WRITE DATA WORD:

S:ADR:W:A:CMD:A:DATA:A:DATA:A:P

ALERT RESPONSE

S:ARA:R:A:ADR:NACK:P:

• Continuously servo one or both supplies to a pro-

grammed voltage.

• Perform a one-time servo of one or both supplies to a

programmed voltage and hold the servo codes in the

controlling IDAC.

• Perform a one time servo of one or both supplies to

a programmed voltage and hold the code(s) in the

controlling IDAC(s) until over/under voltage monitor-

ing detects a fault, at which point a control bit may be

used to allow the LTC2970 to servo back to the initial

voltage target.

• Select any combination of seven possible ADC channels

to be monitored by the ADC.

• Generate instantaneous faults based on user program-

mable over-voltage and under-voltage limits and ﬁxed

IDAC limits. The status of OR’d voltage limit faults and

IDAC faults may be output over GPIO_0 and GPIO_1,

respectively.

• Enable instantaneous faults to set associated latched

faults using the FAULT_EN register. The status of OR’d

latched faults may be signalled using ALERT.

• Conﬁgure the GPIO_0 and GPIO_1 pins to act as inputs

or outputs.

2. I2C Serial Digital Interface

The LTC2970 communicates with a host (master) using

the 2-wire, I2C serial bus interface. The Timing Diagram

shows the timing relationship of the signals on the bus.

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