AD5560JBCZ datasheet(33/68 Pages) AD

33 / 68 page

Data Sheet

AD5560

Rev. D | Page 33 of 68

DIE TEMPERATURE SENSOR AND THERMAL

SHUTDOWN

There are three types of temperature sensors in the AD5560.

•

The first is a temperature sensor available on the MEASOUT

pin and expressed in voltage terms. Nominally at 25°C, this

sensor reads 1.54 V. It has a temperature coefficient of

4.7 mV/°C. This sensor is active during power-down mode.

Die Temp = (VMEASOUT(TSENSE) − 1.54)/0.0047 + 25°C

Based on typical temperature sensor output voltage at

25°C and output scaling factor.

•

The second type of temperature sensor is related to the

thermal shutdown feature in the device. Here, there are

sensors located in the middle of the enabled power stage,

which are used to trip the thermal shutdown. The thermal

shutdown feature senses only the power stages, and the power

stage that it senses is determined by the active stage.

If ranges of <25 mA are selected, the EXTFORCE1 sensor is

monitored. The EXTFORCE1 power stage itself is made

up of three identical stages, but the thermal shutdown is

activated by only one stage (EXTFORCE1B). Similarly, the

EXTFORCE2 stage is made up of two identical output

stages, but the thermal shutdown can be activated by only

one stage (EXTFORCE2A).

The thermal shutdown circuit monitors these sensors and,

in the event of the die temperature exceeding the program-

mable threshold temperature (100°C, 110°C, 120°C, 130°C

(default)), the device protects itself by inhibiting the force

amplifier stage, clearing SW-INH in DPS Register 1 and

flagging the overtemperature event via the open-drain

TMPALM pin, which can be programmed to be either

latched or unlatched. These temperature sensors can be

read via the MEASOUT pin by selecting them in the

diagnostic register (Table 23, VPTAT low and VPTAT

high). They are expressed in voltage and to scale to

temperature. They must be referred to the VTSD reference

voltage levels (see Table 23) also available on MEASOUT.

This set of sensors is not active in power-down mode.

Die Temp_y = {(VPTAT_x − VTSD_low)/[(VTSD_high −

VTSD_low)/(Temp_high – Temp_low)]} + Temp_low

where:

x, y are (high, NPN) and (low, PNP).

Temp_low = −273°C.

Temp_high = +130°C.

•

The third set of temperature sensors is an array of thermal

diodes scattered across the die. These diodes allow the user

to evaluate the temperature of different parts of the die and

are of great use to determine the temperature gradients

across the die and the temperature of the accurate portions

of the die when the device is dissipating high power. For

further details on the thermal array and locations, see the

diagnostic register section in Table 23.

These diodes can be muxed out onto the GPO pin. The

diagnostic register (Address 0x7) details the addressing and

location of the diodes. These can be used for diagnostic

purposes to determine the thermal gradients across the die

and across a board containing many AD5560 devices. When

selected, the anode of each diode is connected to GPO and

the cathode to AGND. The AD5560 evaluation board uses

the ON Semiconductor ADT7461 temperature sensor for

the purpose of analyzing the temperature at different

points across the die.

Note that, when a thermal shutdown occurs, as the force

amplifier is inhibited or tristated, user intervention is required

to reactivate the device. It is necessary to clear the temperature

alarm flag by issuing a read command of Register Address 0x44

(alarm status and clear alarm status register, Table 25), and

then issuing a new write to the DPS Register 1 (SW-INH = 1)

to reenable the force amplifier.

See also the Thermal Considerations section.

MEASURE OUTPUT (MEASOUT)

The measured DUT voltage, current (voltage representation

of DUT current), KSENSE, or die temperature is available on

MEASOUT with respect to AGND. The default MEASOUT

range is the forced voltage range for voltage measure and

current measure (nominally ±12.81 V, depending on reference

voltage and offset DAC) and includes overrange to allow for

system error correction.

The serial interface allows the user to select another MEASOUT

range of (1.025 × VREF) to AGND; this range is suitable for use

with an ADC with a smaller input range.

To allow for system error correction, there is additional gain

for the force function. If this overrange is used as intended,

the output range on MEASOUT scales accordingly.

The MEASOUT line can be tristated via the serial interface.

When using low supply voltages, ensure that there is sufficient

headroom and footroom for the required force voltage range.

VMID VOLTAGE

The midcode voltage (VMID) is used in the measure current

amplifier block to center the current ranges at about 0 A.

This is required to ensure that the quoted current ranges can

be achieved when using offset DAC settings other than the

default. VMID corresponds to 0x8000 or the DAC midcode

value, that is, the middle of the voltage range set by the offset

DAC setting (see Table 15 and Figure 56).

VMID = 5.125 × VREF × (32,768/216) − (5.125 × VREF ×

(OFFSET_DAC_CODE/216))

VMID = 5.125 × VREF × ((32,768 − Offset DAC)/216)

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