SM5846AP_06 Datasheet, PDF (34/36 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
D-ATT attenuation
0
a1
a2
a3
a4
a5
a6
Mode flag 1
1
0
SYNC
TEST1 = 0
HS
FSEL1
FSEL2
Mode flag 2
1
1
MUTE
DITH
OBS
IBS1
IBS2
Mode flag 3
1
1
ASEL1
ASEL2
1
TEST2 = 0
1
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
Bit 8
a7
DEEM
1
0
When a reset is necessary
The device must be reset under the following condi-
tions.
I When power is first applied
I 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).
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.
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.
‘
A 0.01µF 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
‘
Discharge
for Diode
RST
External
Capacitor
C
Internal Pull-up Register
Schmitt Buffer
RST
External
Capacitor
C
Internal Pull-up Register
Schmitt Buffer
SEIKO NPC CORPORATION —34