Data Sheet

LTC9105

REGISTER MAP

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Rev. A | 17 of 22

Table 10. I2C Register Map

Byte

BIT 7

BIT 6

BIT 5

BIT 4

BIT3

BIT 2

BIT 1

BIT 0

1

aux_status

pse_mark[1:0]

aux_thresh

padc_enable

stdby_dis

priority

brownout

2

old_data

ioverflow

current[13:8]

3

current[7:0]

4

padc_data

vpoverflow

voltage_power[13:8]

5

voltage_power[7:0]

Table 11. I2C Register Details

Byte

Bit

Data

Access

Reset

Value

Description

1

7

aux_status

RO

See

description

Auxiliary Status. Returns 1 if an auxiliary supply is detected. Returns 0 if an auxiliary supply is absent.

See Auxiliary Input and Dual-Input Prioritization.

The reset value is determined by the AUX pin state.

1

6:5

pse_mark

RO

See

description

PSE Mark Response. Combine this field with PD requested Class to determine PSE allocated power.

See Table 7.

0 : 0-1 Mark Events, PSE allocated power is Min(PD Requested Class, 13W)

1 : 2-3 Mark Events, PSE allocated power is 25.5W

2 : 4 Mark Events, PSE allocated power is Min(PD Requested Class, 51W)

3 : 5+ Mark Events, PSE allocated power is Min(PD Requested Class, 71.3W)

The reset value is a function of the preceding physical classification result.

1

4

aux_thresh

R/W

0

Auxiliary Threshold Configuration. When set, the LTC9105 AUX pin uses a variable threshold (see

Figure 3). When cleared, the LTC9105 AUX pin uses a 1.05V (typ.) threshold.

1

3

padc_enable

R/W

0

Power ADC Enable. When set, the LTC9105 reports input average power in the voltage_power

field and the padc_data bit is set.

When clear, the LTC9105 reports the input average voltage in the voltage_power field and the

padc_data bit is cleared.

1

2

stdby_dis

R/W

0

Standby Disable. Controls MOSFET state and Automatic MPS feature based on AUX pin state and

priority setting. See Dual-Input Prioritization.

1

1

priority

R/W

See

description

Port Priority. Controls MOSFET state and Automatic MPS feature based on AUX pin state and

stdby_dis setting. See Dual-Input Prioritization.

The reset value is the inverse of the AUX pin state, and is latched on reset exit.

1

0

brownout

R/W1C

0

Brownout Indication. Indicates that the input voltage has fallen below VOFF threshold, then returned to

VON without crossing the VRESET threshold. Remains set until cleared by user. Clear by writing a 1 to

this bit.

2

7

old_data

RO

0

Old Data Indication. This bit is set when an ADC conversion is read over the I2C interface and cleared

when a new ADC conversion is available.

2

6

ioverflow

RO

0

Current Overflow Status. If set, the current readback is an overflow (the measurement was outside the

full scale range of the ADC). Disregard the value in current[13:0] when ioverflow is set.

This field is updated with every ADC conversion.

2

5:0

current[13:8]

RO

0

Current Telemetry MSB. Upper bits of the current telemetry. Combine with current[7:0] for a

complete current telemetry reading.

This field is updated with every ADC conversion.

3

7:0

current[7:0]

RO

0

Current Telemetry LSB. Lower bits of the current telemetry. Combine with current[13:8] for a

complete current telemetry reading.

Representing 246.8μA/LSb (14-bit) with an offset of 0x2000. Full scale range ±2.022A. All values are

typical and assume RSNSP-SNSN = 50mΩ.

This field is updated with every ADC conversion.

4

7

padc_data

RO

0

Power Telemetry Indicator. Returns 1 if voltage_power[13:0] contains power data. Returns 0 if

voltage_power[13:0] contains voltage data.

This field is updated with every ADC conversion.