CS5463
The temperature update rate is a function of the number
of ADC samples. With MCLK = 4.096 MHz and K = 1
the update rate is:
XOUT
2240 samples
---------------------------------------
= 0.56 sec
C1
(MCLK ⁄ K) ⁄ 1024
Oscillator
Circuit
The Cycle Count Register (N) must be set to a value
greater then one. Status bit TUP in the Status Register,
indicates when the Temperature Register is updated.
XIN
C2
The Temperature Offset Register sets the zero-degree
measurement. To improve temperature measurement
accuracy, the zero-degree offset may need to be adjust-
ed after the CS5463 is initialized. Temperature offset
calibration is achieved by adjusting the Temperature
DGND
C1 = C2 = 22 pF
Offset Register (T ) by the differential temperature
off
Figure 10. Oscillator Connection
(∆T) measured from a calibrated digital thermometer
and the CS5463 temperature sensor. A one degree ad-
justment to the Temperature Register (T) is achieved by
5.9 System Initialization
-4
Upon powering up, the digital circuitry is held in reset
until the analog voltage reaches 4.0 V. At that time, an
eight XIN clock period delay is enabled to allow the os-
cillator to stabilize. The CS5463 will then initialize.
adding 2.737649x10 to the Temperature Offset Regis-
ter (T ). Therefore,
off
–4
T
= Toff + (∆T × 2.737649 ⋅ 10
)
off
if T = -0.09104831 and ∆T = -7.0 (oC), then
A hardware reset is initiated when the RESET pin is as-
serted with a minimum pulse width of 50 ns. The RE-
SET signal is asynchronous, with a Schmitt Trigger
input. Once the RESET pin is de-asserted, an eight XIN
off
T
= – 0.09104831 + (–7.0 × 2.737649 ⋅ 10–4) = –0.09296466
off
clock period delay is enabled
.
or 0xF419BC (2’s compliment notation) is stored in the
Temperature Offset Register (T ).
off
A software reset is initiated by writing the command
0x80. After a hardware or software reset, the internal
registers (some of which drive output pins) will be reset
to their default values. Status bit DRDY in the Status
Register, indicates the CS5463 is in its active state and
ready to receive commands.
To convert the Temperature Register (T) from a Celsius
scale (oC) to a Fahrenheit scale (oF) utilize the formula
o
9 o
5
(
)
F = -- C+ 17.7778
Applying the above relationship to the CS5461A tem-
perature measurement algorithm
5.10 Power-down States
The CS5463 has two power-down states, Stand-by and
Sleep. In the stand-by state all circuitry except the volt-
age reference and crystal oscillator is turned off. To re-
turn the device to the active state a power-up command
is sent to the device.
–4
o
o
9
--
⎛
⎝
⎞
⎛
⎝
⎞
⎠
T 〈 F〉 =
×T
T 〈 C〉 +
T
+ (17.7778 × 2.737649 ⋅ 10
)
⎠
gain
off
5
In Sleep state all circuitry except the instruction decoder
is turned off. When the power-up command is sent to
the device, a system initialization is performed (See
Section 5.9 System Initialization on page 20).
If T = -0.09296466 and T
scale, then the modified values are T = -0.08809772
= 23.799 for a Celsius
gain
off
off
(0xF4B937) and T
Fahrenheit scale.
= 42.8382 (0x55AD29) for a
gain
5.11 Oscillator Characteristics
5.8 Voltage Reference
XIN and XOUT are the input and output of an inverting
amplifier configured as an on-chip oscillator, as shown
in Figure 10. The oscillator circuit is designed to work
with a quartz crystal. To reduce circuit cost, two load ca-
pacitors C1 and C2 are integrated in the device, from
XIN to DGND, and XOUT to DGND. PCB trace lengths
The CS5463 is specified for operation with a +2.5 V ref-
erence between the VREFIN and AGND pins. To utilize
the on-chip 2.5 V reference, connect the VREFOUT pin
to the VREFIN pin of the device. The VREFIN can be
used to connect external filtering and/or references.
20
DS678PP1
CIRRUS [ CIRRUS LOGIC ]
