Datasheet

AD5410/AD5420 Data Sheet
Rev. F | Page 28 of 32
MICROPROCESSOR INTERFACING
Microprocessor interfacing to the AD5410/AD5420 is via a serial
bus that uses a protocol compatible with microcontrollers and
DSP processors. The communication channel is a 3-wire (mini-
mum) interface consisting of a clock signal, a data signal, and a
latch signal. The AD5410/AD5420 require a 24-bit data-word
with data valid on the rising edge of SCLK.
For all interfaces, the DAC output update is initiated on the
rising edge of LATCH. The contents of the registers can be read
using the readback function.
THERMAL AND SUPPLY CONSIDERATIONS
The AD5410/AD5420 are designed to operate at a maximum
junction temperature of 125°C. It is important that the device
not be operated under conditions that cause the junction tempera-
ture to exceed this value. Excessive junction temperature can
occur if the AD5410/AD5420 are operated from the maximum
AV
DD
, while driving the maximum current (24 mA) directly to
ground. In this case, the ambient temperature should be controlled
or AV
DD
should be reduced.
At the maximum ambient temperature of 85°C, the 24-lead
TSSOP can dissipate 1.14 W, a nd the 40-Lead LFCSP can
dissipate 1.21 W.
To ensure that the junction temperature does not exceed 125°C
while driving the maximum current of 24 mA directly into
ground (also adding an on-chip current of 4 m A), AV
DD
should
be reduced from the maximum rating to ensure that the
package is not required to dissipate more power than previously
stated (see Table 21, Figure 53, and Figure 54).
0
0.5
1.0
1.5
2.0
2.5
40 45 50 55 60 65 70 75 80 85
A
MB
IENT TEMPERATURE (°C)
POWER DISSIPATION (W)
07027-055
LF
C
SP
TSS
O
P
Figure 53. Maximum Power Dissipation vs. Ambient Temperature
65
60
55
50
45
40
35
30
25
25 35 45 55
65
TSSOP
LFCSP
75 85
AMBIENT TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
07027-054
Figure 54. Maximum Supply Voltage vs. Ambient Temperature
Table 21. Thermal and Supply Considerations
Consideration TSSOP LFCSP
Maximum Allowed Power
Dissipation When Operating
at an Ambient Temperature
of 85°C
W1.14
35
85
125
max
=
−
=
Θ
−
JA
A
T
J
T
W1
.2
1
33
85125
max
=
−
=
Θ
−
JA
A
T
J
T
Maximum Allowed Ambient
Temperature When Operating
from a Supply of 40 V/60 V
and Driving 24 mA Directly to
Ground
( )
C8635028.040125max °=××−=Θ×−
JADJ
PT
( )
C7033028.060125max °=××−=Θ×−
JADJ
PT
Maximum Allowed Supply
Voltage When Operating at
an Ambient Temperature of
85°C and Driving 24 mA
Directly to Ground
V40
35028.0
85125
max
=
×
−
=
Θ
×
−
JADD
AJ
AI
T
T
V43
33
028.0
85125
max
=
×
−
=
Θ×
−
JA
DD
A
J
AI
T
T