SM5846AP Datasheet, PDF (35/36 Pages) Nippon Precision Circuits Inc – Multi-function Digital Filter

SM5846AP
Serial data format
Register
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
Bit 8
D-ATT attenuation
0
a1
a2
a3
a4
a5
a6
a7
Mode flag 1
1
0
SYNC TEST1 = 0
HS
FSEL1
FSEL2
DEEM
Mode flag 2
1
1
MUTE
DITH
OBS
IBS1
IBS2
1
Mode flag 3
1
1
ASEL1
ASEL2
1
TEST2 = 0
1
0
Address information is displayed in double-line cells of the table.
Test bits (mode flag 1 bit 4 and mode flag 3 bit 6) should be set to 0.
System Reset
When a reset is necessary
The device must be reset under the following condi-
tions.
s When power is first applied
s When the LRCI clock or system clock stop
Reset input conditions
The RST input is active LOW.
At power-ON reset, RST must go LOW and then go
HIGH after the XTI and LRCI clocks stabilize (reset
release).
A 0.01 µF external capacitor is recommended. How-
ever, the time constant can be lengthened if longer
time is required for the XTI and LRCI clocks to sta-
bilize after power-ON.
The external capacitor discharges through the inter-
nal pull-up resistor at power-OFF as this is the only
possible discharge path. This could cause reset fail-
ure if power is reapplied while the external capacitor
is discharging. Therefore, a diode should be con-
nected between RST and VDD to quickly discharge
the capacitor and ensure correct power-ON reset
operation.
External power-ON reset circuit
Reset timing
The internal arithmetic registers and output sequence
are initialized on the rising edge of the LRCI clock
after reset release. The internal control flags and D-
ATT attenuation register are initialized after RST
goes LOW. Outputs DOL and DOR are tied LOW
while RST is LOW.
Discharge
for Diode
RST
External
Capacitor
C
Internal Pull-up Register
Schmitt Buffer
Power-ON reset using a capacitor
The RST input configuration is a Schmitt-trigger
input with a pull-up resistor, which means that a sim-
ple power-ON reset circuit can be made by connect-
ing a capacitor between RST and VSS as shown
below.
‘
RST
External
Capacitor
C
Internal Pull-up Register
Schmitt Buffer
NIPPON PRECISION CIRCUITS—35