CS5461 View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
CS5461 Datasheet PDF : 45 Pages
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CS5461
From this equation the value of ‘PR’ is shown as:
PR = -------------------I---R--------------------- = ----------------1---0----0---H-----z-----------------
-V-----V---n---o---m--- × --V-----I--n--o---m----
250mV 250mV
1----3--2----m-----V--- × 1---1----2---.-5---m-----V---
250mV 250mV
Therefore the Pulse-Rate Register is set to
~420.875 Hz, or 0x00349C.
EXAMPLE #2: The required number of pulses per
unit energy present at EOUT is specified to be
500 pulses/kW-hr; given that the maximum
line-voltage is 250 V (RMS) and the maximum
line-current is 20 A (RMS). In such a situation, the
nominal line voltage and current do not determine
the appropriate pulse-rate setting. Instead, the max-
imum line levels must be considered. As before, the
given maximum line-voltage and line-current lev-
els are used to determine KV and KI:
KV = 150 mV / 250 V = 0.0006
KI = 150 mV / 20 A = 0.0075 Ω
Again the sensor gains are calculated such that the
maximum line-voltage and line-current levels will
measure as 0.6 in the RMS Voltage Register and
RMS Current Register.
With voltage and current channel input ranges set
to 10x, the required Pulse-Rate Register setting is
determined using the following equation:
PR
=
500
--p---u---l--s---e---s--
kW ⋅ hr
⋅
---1----h---r----
3600s
⋅
---1----k---W-------
1000W
⋅
-2---5--0----m-----V---
KV
⋅
-2--5---0----m-----V---
KI
Therefore PR = ~1.929 Hz.
Note that the Pulse-Rate Register cannot be set to a
frequency of exactly 1.929 Hz. The closest setting
that the Pulse-Rate Register can obtain is
0x00003E = 1.9375 Hz. To improve the accuracy,
either gain register can be programmed to correct
for the round-off error in PR. This value would be
calculated as
Ign or Vgn = ---P----R----- ≅ 1.00441 = 0x404830
1.929
When MCLK/K is not equal to 4.096 MHz, the re-
sult for ‘PR’ that is calculated for the Pulse-Rate
Register must be scaled by a correction factor of:
4.096 MHz / (MCLK/K). For MCLK/K of
3.05856 MHz the result is scaled by 4.096/3.05856
to get a final PR result of ~2.583 Hz.
5.6 Auto-Boot Mode Using EEPROM
When the CS5461 MODE pin is left unconnected,
the CS5461 is in normal operating mode, called
host mode. When this pin is set to logic high, the
CS5461 auto-boot mode is enabled. In auto-boot
mode, the CS5461 is configured to request a mem-
ory download from an external serial EEPROM.
Auto-Boot mode allows the CS5461 to operate
without the need for a microcontroller.
5.6.1 Auto-Boot Configuration
Figure 13 shows the typical connections between
the CS5461 and a serial EEPROM for proper au-
to-boot operation. In this mode, CS and SCLK are
driven outputs. During the auto-boot sequence, the
CS5461 drives CS low, provides a clock output on
SCLK, and drives out-commands on SDO. It re-
ceives the EEPROM data on SDI. The serial EE-
PROM must be programmed with the
user-specified commands and register data that will
be used by the CS5461 to change any of the default
register values and begin conversions.
VD+
5K
/EOUT
/EDIR
CS5461
SCK
SDI
SDO
MODE
/CS
Mech. Counter
or
Stepper Motor
5K
EEPROM
SCK
SO
SI
/CS
Connector to Calibrator
Figure 13. Typical Interface of EEPROM to
26
DS546F2
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