ADM1260 datasheet(21/71 Pages) AD

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ADM1260

Rev. 0 | Page 21 of 71

INTERCHIP BUS

In addition to local device conditions, a number of different

ICB messages can affect the operation of the SE. These messages

are used by the ADM1260 to coordinate the sequencing

activities, and to inform other devices of faults within the

system.

There are four basic types of ICB messages.



Sequence action



Timeout fault



Monitor fault



Black box trigger

The sequence action message has two forms. In a device to device

form (the first form), this message is used to hand over sequencing

responsibility from one device to the another. The transfer of

sequencing control is done using a ping-pong handshake to ensure

a robust handover of control. In the second form, the message is

broadcast to all devices and instructs them to execute the sequence

condition of the active SE state. All devices connected by the

ICB advance their state machines together in lock step to

maintain a coherent overall system state.

The sequence condition can be set to generate a sequence action

message that is sent to a specific device, or is broadcast to all devices.

The sequence condition in the SE state must be set to wait for a

ping (from a specific device or from a broadcast) for the device

to receive and act upon it.

The timeout and monitor fault messages are always broadcast

messages. They are used by one device to inform all other devices

connected to the ICB that a timeout or monitor fault has occurred,

and to follow the exit state defined in the active SE state.

The timeout and monitor messages are always active on the

ADM1260. The timeout and monitor conditions do not need to

be programmed as part of the SE definition to respond to the

messages being received on the ICB.

The black box trigger is a broadcast message automatically sent

by an ADM1260 when a sequence condition causes the device

to enter a state where the black box trigger is enabled.

In normal operation, the ADM1260 evaluation software, ADI

Power Studio, generates a virtual sequence for all the devices

that share the same ICB. The software automatically inserts the

necessary ICB messages and generates the sequence engine of

each device connected to the ICB. In practice, the end user does

not need to insert the ICB message handling into the SE.

The ICB must be pulled up for the SE to progress; otherwise,

the devices remain in a reserved state.

The SE follows the fault handler path in case of an ICB bus fault

or ping-pong fault if one of the devices in the sequence is non-

operational.

ICB Message Address

Each device on the ICB is assigned a 4-bit address, which is

automatically configured by the GUI. This address is used for

device to device sequence action messages. The ADM1260

supports up to four devices on the ICB.

SE APPLICATION EXAMPLE

The application in this section demonstrates the operation of

the SE. Figure 29 shows how the simple building block of a

single SE state can be used to build a power-up sequence for a

three-supply system. Table 8 lists the PDOx outputs for each

state in the same SE implementation. In this system, a good 5 V

supply on the VP1 pin and the VX1 pin held low are the triggers

required to start a power-up sequence. Next, the sequence turns

on the 3.3 V supply, then the 2.5 V supply (assuming successful

turn on of the 3.3 V supply). When all three supplies turn on

correctly, the power-good state is entered, where the SE remains

until a fault occurs on one of the three supplies or until it is

instructed to go through a power-down sequence by VX1 going

high. Faults are dealt with throughout the power-up sequence

on a case by case basis. The following three sections in this data

sheet (the Sequence Detector section, the Monitoring Fault

Detector section, and the Timeout Detector section) describe

the individual blocks and use the sample application shown in

Figure 29 to demonstrate the actions of the SE.

Table 8. PDO Outputs for Each State

PDOx Output

Sequence State1

IDLE1

IDLE2

EN3V3

EN2V5

DIS3V3

DIS2V5

PWRGD

FSEL1

FSEL2

PDO1 = 3V3ON2

PDO2 = 2V5ON3

PDO3 = FAULT4

1 The various sequence states are described in Table 7.

2 3V3ON means that a particular PDOx pin enables the signal of the 3.3 V LDO.

3 2V5ON means that a particular PDOx pin enables the signal of the 2.5 V LDO.

4 PDO3 is used to send a fault signal to the microcontroller or FPGA.

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