ad5504 Analog Devices, Inc., ad5504 Datasheet - Page 12

• Manufacturer Part Number: ad5504
• Description: High Voltage, Quad Channel 12-bit Voltage Output Dac
• Manufacturer: Analog Devices, Inc.

AD5504
LDAC FUNCTION
The DAC outputs can be updated using the hardware LDAC
pin. LDAC is normally high. On the falling edge of LDAC data
is copied from the Input registers to the DAC registers and the
DAC outputs are updated simultaneously (Asynchronous
update mode, see Figure 3). If the LDAC is kept low, or is low
on the falling edge of the 16
register and DAC output are updated automatically
(Synchronous update mode, see Figure 3).
TEMPERATURE SENSOR
The AD5504 can be programmed to enter thermal shutdown
mode if the temperature on the die exceeds 130°C. Setting bit 1
of the Control register (see Table 9) to 0 enables this function
(enabled by default on power-up). In thermal shutdown mode
the analog section of the device is powered down, 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.
th
SCLK the appropriate DAC
Rev. Pr B | Page 12 of 15
POWER DISSIPATION
Drawing current from any of the voltage output pins causes a
temperature rise in the die and package of the AD5504. The die
temperature (T
operation. If bit 1 of the Control register is set and the die
temperature exceeds 130°C the AD5504 enters thermal
shutdown mode as described in the previous section. The
amount of heat generated can be calculated using the formula
T
Where:
POWER SUPPLY SEQUENCING
The power supplies for the AD5504 can be applied in any order
without affecting the device. However, in order to ensure that
the serial interface operates correctly after power up the digital
input pins should not be allowed to float. Floating pins may be
interpreted as SCLK, SDI or SYNC pulses by the AD5504 if they
cross the switching thresholds of the digital input circuitry. The
digital input pins can be connected to pull-up (to V
pull-down (to DGND) resistors as required.
J
= T
T
T
P
θ
Absolute Maximum Ratings for this value).
JA
TOTAL
J
A
is the package junction temperature
is the ambient temperature
is the thermal impedance of the AD5504 package (see the
A
+ (P
is the total power being consumed by the AD5504
TOTAL
J
) should not exceed 130°C for normal
× θ
JA
Preliminary Technical Data
)
LOGIC
) or