ADP1046AACPZ-R7 datasheet(26/88 Pages) AD

26 / 88 page

ADP1046A

Data Sheet

Rev. 0 | Page 26 of 88

Figure 35 shows the possible signals on the share bus.

LOGIC 1

LOGIC 0

IDLE

BIT

tBIT

Figure 35. Share Bus High, Low, and Idle Bits

The length of a bit (tBIT) is fixed at 10 μs. A Logic 1 is defined as

a high-to-low transition at the start of the bit and a low-to-high

transition at 75% of tBIT. A Logic 0 is defined as a high-to-low

transition at the start of the bit and a low-to-high transition at

25% of tBIT.

The bus is idle when it is high during the whole period of tBIT.

All other activity on the bus is illegal. Glitches up to tGLITCH

(200 ns) are ignored.

The digital word that represents the current information is eight

bits long. The ADP1046A takes the eight MSBs of the CS2 read-

ing and uses this reading as the digital word (see Figure 36).

Digital Share Bus Scheme

Each power supply compares the digital word that it is outputting

with the digital words of all the other supplies on the bus.

Round 1

In Round 1, every supply first places its MSB on the bus. If a

supply senses that its MSB is the same as the value on the bus, it

continues to Round 2. If a supply senses that its MSB is less than

the value on the bus, it means that this supply must be a slave.

When a supply becomes a slave, it stops communicating on the

share bus because it knows that it is not the master. The supply then

increases its output voltage in an attempt to share more current.

If two units have the same MSB, they both continue to Round 2

because either of them may be the master.

Round 2

In Round 2, all supplies that are still communicating on the bus

place their second MSB on the share bus. If a supply senses that

its MSB is less than the value on the bus, it means that this supply

must be a slave and it stops communicating on the share bus.

Round 3 to Round 8

The same algorithm is repeated for up to eight rounds to allow

supplies to compare their digital words and, in this way, to

determine whether each unit is the master or a slave.

Digital Share Bus Configuration

The digital share bus can be configured in various ways. The band-

width of the share bus loop is programmable in Register 0x29[2:0].

The extent to which a slave tries to match the current of the master

is programmable in Register 0x2A[3:0]. Enable the digital share

bus by setting Register 0x29[3] to 1.

CURRENT

SENSE

ADC

1 LSB = 29.3µV

35mV/29.3µV = 1195

MASTER

35mV

–

DIGITAL

WORD

DIGITAL

FILTER

÷16

12 BITS

1195 DEC

0x4AB

8 BITS

74 DEC

0x4A

SHAREi

CS2+

CS2–

VDD

BUS

8-BIT

WORD

0xB5

8-BIT

WORD

0x4A

SHAREo

IOUT = 35A

1mΩ

PSU A

Figure 36. How the Share Bus Generates the Digital Word to Place on the Digital Share Bus

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