MAX14820 Datasheet, PDF(18/29 Page) Maxim Integrated Products

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MAX14820

IO-Link Device Transceiver

Thermal Protection and Considerations

The internal LDOs and drivers can generate more power

than the package for the devices can safely dissipate.

Ensure that the driver LDO loading is less than the pack-

age can dissipate. Total power dissipation for the device

is calculated using the following equation:

PTOTAL = PC/Q + PDO + P5 + PLDO33 + PQ +

PCLCQ + PCLDI

where PC/Q is the power generated in the C/Q driver,

PDO is the power dissipated by the DO driver, P5 and

PLDO33 are the power generated by the LDOs, PQ is the

quiescent power generated by the devices, and PCLCQ

and PCLDI are the power generated in the C/Q and DI

current sinks.

Ensure that the total power dissipation is less than the

limits listed in the Absolute Maximum Ratings section.

Use the following to calculate the power dissipation (in

mW) due to the C/Q driver:

PC/Q = [IC/Q(max)] Ã [0.5 + 7 Ã IC/Q(max)]

Calculate the internal power dissipation of the DO driver

using the following equation:

PDO = [IDO(max)] Ã [0.5 + 7 Ã IDO(max)]

Calculate the power dissipation in the 5V LDO, V5, using

the following equation:

P5 = (VLDOIN - V5) Ã I5

where I5 includes the ILDO33 current sourced from

LDO33.

Calculate the power dissipated in the 3.3V LDO, LDO33,

using the following equation:

PLDO33 = 1.7V Ã ILDO33

Calculate the quiescent power dissipation in the device

using the following equation:

PQ = 5mA Ã VCC(max)

If the current sinks are enabled, calculate their associ-

ated power dissipation as:

PCLCQ = 7mA Ã VC/Q(max)

PCLDI = 7mA Ã VDI(max)

Overtemperature Warning

Bits in the Status and Mode registers are set when the

temperature of the device exceeds +115NC (typ). The

OTempInt bit in the Status register is set and IRQ asserts

when the OTemp bit in the Mode register is set. Read the

Status register to clear the OTempInt bit and IRQ.

The OTemp bit is cleared when the die temperature falls

to +95NC.

The device continues to operate normally unless the

die temperature reaches the +150NC thermal shutdown

threshold, when the device enters thermal shutdown.

Thermal Shutdown

All regulators and the C/Q and DO output drivers are

automatically switched off when the internal die tempera-

ture exceeds the +150NC (typ) thermal shutdown thresh-

old. SPI communication is not available during a thermal

shutdown event.

Regulators are automatically switched on when the inter-

nal die temperature falls below the thermal shutdown

threshold plus hysteresis. The internal registers return to

their default state when the V5 regulator is switched on.

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