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Data Sheet

ADP1052

Rev. B | Page 35 of 113

TEMPERATURE LINEARIZATION SCHEME

The ADP1052 linearization scheme is based on a combination of

a thermistor (R25 = 100 kΩ, 1%), an external resistor (16.5 kΩ,

1%), and the 46 µA current source, preselected for best perfor-

mance when linearizing measured temperatures in the industrial

range.

The NTC thermistor that is required must have a resistance of

R25 = 100 kΩ, 1%, such as the NCP15WF104F03RC (beta = 4250,

1%). It is recommended that 1% tolerance be used for both the

resistor and beta values. The linearization equations show the

relationship between the RTD voltage, VRTD (in volts), and

temperature reading, T (in degrees Celsius).

If T < 104°C,

VRTD = (130 − T) ×

256

If T ≥ 104°C,

VRTD = (156 − T) ×

512

where T represents the temperature reading in Register 0x8D.

Figure 37 shows the temperature linearization curves.

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

TEMPERATURE (°C)

100 110 120 130

LINEARIZATION VOLT-TEMP CURVE

ACTUAL VOLT-TEMP CURVE

Figure 37. Temperature Linearization Scheme Curves

Using the internal linearization scheme, the READ_TEMPERA-

TURE command (Register 0x8D) returns the current temperature

in degrees Celsius. For overtemperature protection, the user can

directly set the OT_FAULT_LIMIT command (Register 0x4F) in

degrees Celsius. See the OT_FAULT and OT_WARNING section

for more information.

PMBUS PROTECTION COMMANDS

VOUT Overvoltage Protection (OVP)

The VOUT overvoltage protection feature in the ADP1052

follows PMBus specifications. The limits are programmed in

the VOUT_OV_FAULT_LIMIT command (Register 0x40) to

correspond to the voltage between 75% and 150% of the nominal

output voltage. The responses are programmed using the VOUT_

OV_FAULT_RESPONSE command (Register 0x41). The

VOUT_OV_FAULT flag (Register 0x78[5], Register 0x79[5],

and Register 0x7A[7]) is set when the voltage reading exceeds the

overvoltage limit.

In a direct parallel system, multiple power supply units are

connected directly in parallel without any OR’ing device. An

overvoltage condition in one power supply can raise the common

bus voltage, causing the activation of overvoltage protection in

the other power supplies connected to the common bus. As a

result of this overvoltage protection action, the common bus

may fail. The ADP1052 provides a highly flexible, conditional

overvoltage protection function for redundant control in a direct

parallel system. It consists of an overvoltage detection block, a

modulation flag triggering block, and an overvoltage response

block (see Figure 38).

VOUT_OV_FAULT

DEBOUNCE

REG 0xFE26

OVP

VS–

VOUT_OV_FAULT_RESPONSE

REG 0x41

MODULATION

VALUE

MODULATION

THRESHOLD

REG 0xFE6B

AND

EXTENDED

VOUT_OV_FAULT_RESPONSE

REG 0xFE01

VOUT_OV_FAULT_LIMIT

REG 0x40

VOUT_OV_FAULT

REG 0x7A[7]

OVP SELECTION

REG 0xFE6C[0]

LARGE_MODULATION

REG 0xFE6C[2]

DAC

Figure 38. VOUT Overvoltage Protection Circuit Implementation

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