Datasheet

Data Sheet AD5504
Rev. B | Page 15 of 20
TEMPERATURE SENSOR
The AD5504 has an integrated temperature sensor that causes
the part to enter thermal shutdown mode when the temperature
on the die exceeds 110°C. In thermal shutdown mode, the
analog section of the device powers down and the DAC outputs
are disconnected, but the digital section remains operational,
which is equivalent to setting the power-down bit in the control
register. To indicate that the AD5504 has entered temperature
shutdown mode, Bit 0 of the control register is set to 1 and the
ALARM
pin goes low. The AD5504 remains in temperature
shutdown mode with Bit 0 set to 1 and the
ALARM
pin low, even
if the die temperature falls, until Bit 0 in the control register is
cleared to 0.
POWER DISSIPATION
Drawing current from any of the voltage output pins causes a
temperature rise in the die and package of the AD5504. The
package junction temperature (T
J
) should not exceed 130°C for
normal operation. If the die temperature exceeds 110°C, the
AD5504 enters thermal shutdown mode as described in the
Temperature Sensor section.
The amount of heat generated can be calculated using the
formula
T
J
= T
A
+ (P
TOTAL
× θ
JA
)
where:
T
J
is the package junction temperature.
T
A
is the ambient temperature.
P
TOTAL
is the total power being consumed by the AD5504.
θ
JA
is the thermal impedance of the AD5504 package (see the
Absolute Maximum Ratings section for this value).
POWER SUPPLY SEQUENCING
The power supplies for the AD5504 can be applied in any order
without affecting the device. However, the AGND and DGND
pins should be connected to the relevant ground plane before
the power supplies are applied. None of the digital input pins
(SCLK, SDI,
SYNC
,
R_SEL
and
CLR
) should be allowed to float
during power up. The digital input pins can be connected to
pull-up (to V
LOGIC
) or pull-down (to DGND) resistors as
required.