AD5560 Analog Devices, Inc., AD5560 Datasheet - Page 31

• Manufacturer Part Number: AD5560
• Description: 1.2 A Programmable Device Power Supply With Integrated 16-bit Level Setting Dacs
• Manufacturer: Analog Devices, Inc.

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
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 (
high). They are expressed in voltage and to scale to
temperature. They must be referred to the VTSD reference
voltage levels (see
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.
Table 23
Table 23
(TSENSE)
) also available on MEASOUT.
, VPTAT low and VPTAT
− 1.54)/0.0047 + 25°C
Rev. B | Page 31 of 60
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.
MEASURE OUTPUT (MEASOUT)
The measured DUT voltage, current (voltage representation
of DUT current), K
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.
V
The midcode voltage (V
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. V
value, that is, the middle of the voltage range set by the offset
DAC setting (see Table 15 and Figure 54).
or
MID
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.
V
(OFFSET_DAC_CODE/2
V
VOLTAGE
MID
MID
MID
= 5.125 × VREF × (32,768/2
= 5.125 × VREF × ((32,768 − Offset DAC)/2
corresponds to 0x8000 or the DAC midcode
SENSE
, or die temperature is available on
MID
) is used in the measure current
16
))
16
) − (5.125 × VREF ×
AD5560
16
)