ADIN1111CCPZ-R7 datasheet(12/109 Pages) AD

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Data Sheet

ADIN1111

THEORY OF OPERATION

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which PHY is the leader and which is the follower. Leader and

follower assignment does not generally matter.

Software Configuration

The leader and follower configuration bit (CFG_MST) is used to

configure the PHY role. This bit is only used when autonegotiation

is disabled. Otherwise, this bit is set or reset during the autonego-

tiation process (see the Autonegotiation section).

Table 8. CFG_MST Settings

Bit Setting

Description

Prefer follower

Prefer leader

AUTONEGOTIATION

The ADIN1111 uses the autonegotiation capability in accordance

with IEEE 802.3 Clause 98, providing a mechanism for exchanging

information between PHYs to allow link partners to agree to a

common mode of operation. During the autonegotiation process,

the PHY advertises its own capabilities and compares to those

received from the link partner. The concluded operating mode is the

transmit amplitude mode and leader/follower preference common

across the two devices.

If a link is dropped, the autonegotiation process restarts automati-

cally. An autonegotiation restart can also be requested by writing

to the autonegotiation restart bit (AN_RESTART) in the autonego-

tiation control register.

The autonegotiation process takes some time to complete, depend-

ing on the number of pages exchanged, but is always the fastest

way to bring up a link. Clause 98 of the IEEE 802.3 standard details

the timers related to autonegotiation.

Note that autonegotiation is enabled by default for the ADIN1111,

and it is strongly recommended that autonegotiation is always

enabled.

Transmit Amplitude Resolution

Autonegotiation is used to resolve the transmit amplitude resolution.

The PHY can be configured to support both 1.0 V p-p and 2.4 V

p-p transmit levels or to operate with 1.0 V p-p transmit level only

through the hardware configuration (see Table 14). This configura-

tion can also be done in software using the 10BASE-T1L high level

transmit operating mode ability (AN_ADV_B10L_TX_LVL_HI_ABL)

and 10BASE-T1L high level transmit operating mode request

(AN_ADV_B10L_TX_LVL_HI_REQ) register bits.

To operate at 2.4 V p-p transmit level, both the local and remote

PHYs must advertise that they are capable of operating at 2.4

V, and at least one PHY must request 2.4 V p-p transmit level

operation.

If it is required to only operate the PHY at 1.0 V p-p transmit

level operation, AN_ADV_B10L_TX_LVL_HI_ABL must be 0 so

that 2.4 V p-p transmit level operation is not advertised. In this

case, autonegotiation can only resolve to 1.0 V p-p transmit level

operation, irrespective of what setting the remote PHY advertises.

Leader/Follower Resolution

Autonegotiation is also used to resolve leader or follower status.

The PHY can be configured to prefer follower or prefer leader

through the hardware configuration (see Table 13). If autonegotia-

tion is disabled, the MS_SEL hardware configuration pin sets the

default leader/follower selection. Note that the recommended use of

the ADIN1111 is with autonegotiation enabled.

During autonegotiation, when prefer follower is selected, and the

remote end is prefer or forced leader, the local PHY is set to

follower (and remote to leader). When the remote end is prefer

or forced follower, the local PHY is set to leader (and remote to

follower).

MDI CIRCUITRY

The media dependent interface (MDI) connects the ADIN1111 to the

Ethernet network via a twisted wire pair.

The ADIN1111 provides a two pin MDI with internal termination

resistors and an internal hybrid to connect the ADIN1111 to the

Ethernet network directly via a twisted wire pair.

Figure 10, Figure 11 and Figure 12 show the topologies and values

for the components.

The component values are as follows:

►

D1, D2: protection components low capacitance (<5 pF), low-

voltage (standoff voltage ≥3.3 V) TVS.

►

C1, C2: 0.22 µF, 60 V rating. If a transformer with low inductance

is 350 µH, then C1 and C2 may need to increase to 0.47 µF (to

comply with droop specification per IEEE 802.3).

►

R7, R8: optional resistors preventing built up charge on the C1

and C2 capacitors (100 kΩ to ~ MΩ).

►

C3, C4: 47 pF to 100 pF, ±5% tolerance.

►

D3: protection component low capacitance TVS (≤100 pF). It is

important that the TVS diode has low capacitance.

►

L1 transformer: provides galvanic isolation.

►

Must be able to operate in the frequency range from 100 kHz

to 20 MHz.

►

Inductance > 350 µH.

►

L2 common-mode inductor: ≥220 µH, low-leakage inductance

<0.5 µH.

►

L3 power inductor: power coupling for advanced physical layer

(APL) and non APL devices.

►

APL: >880 µH differentially to achieve 10% max droop.

►

Recommended >220 µH coupled inductor (two inductors on

a common magnetic core).

►

Or two >440 µH individual inductors.

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