SM9103M Datasheet, PDF (13/14 Pages) Nippon Precision Circuits Inc – DVDRAM Head Amplifier LSI

SM9103M
Offset Correction
The SM9103M has built-in offset correction circuits
for tracking and focus. During offset correction, the
internal the device operates in RAM read mode, and
FSUB and TSUB operate at maximum gain
(+14 dB). The outputs on FSUB, FADD and TSUB
are indeterminate. Also, inputs T1, T2, T3, T4 and
F1, F2 may be ignored. After correction is complete,
the FSUB and TSUB gain settings return to their
default values (0 dB).
Offset correction is performed under the following
conditions:
s When power is applied.
s When the supply drops below 2.8 ± 0.9 V and then
rises to above 3.8 ± 0.6 V.
s When sleep mode operation is cancelled.
s When the serial interface bit CS1 is 1. Note that if
SL1 is also 1, then SL1 has priority.
Table 4. Offset correction setting
CS1
Offset correction¹
0
No correction
1
Correction
1. Default is No correction
Sleep Mode
The SM9103M features a sleep mode which can be
used when the device is not operating to significantly
reduce current consumption. The sleep mode is con-
trolled by serial interface bit SL1.
Preset Function
When power is applied or after offset correction, all
serial interface flags are reset to their default values.
If the voltage falls below 2.8 ± 0.9 V during offset
correction, then correction stops and does not restart
until the supply recovers to above 3.8 ± 0.6 V.
During offset correction, the CALREQ output is held
HIGH. CALREQ goes LOW after correction stops.
The SM9103M also incorporates a temperature
detect function which detects temperature changes of
20 ± 5 °C from the time the initial correction is per-
formed. If a temperature change is detected, CAL-
REQ goes HIGH and the device waits for an offset
correction instruction.
Note that when both WRITE and MODE are HIGH,
offset correction is inactive and the output appears
uncorrected. However, if a correction start condition
occurs when correction is inactive, such as the cor-
rection flag CS1 set to 1, then correction operation is
initiated internally but does not appear at the output
unless correction is activated prior to correction
operation finishing.
Once correction has been made inactive, the output
remains uncorrected even if correction is subse-
quently reactivated. In this case, the output remains
uncorrected until a valid correction start condition is
detected.
Table 5. Sleep mode settings
SL1
Sleep mode¹
LOW
OFF
HIGH
ON
1. Default is OFF
Mode description
Normal operation
Sleep condition
Flags TG3 to TG0 and FG3 to FG0 are also set to
their default values in sleep mode.
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