PIC12F635ESLASHP datasheet(89/196 Pages) MICROCHIP

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Preliminary

DS41232B-page 87

PIC12F635/PIC16F636/639

TABLE 11-1:

TYPICAL OUTPUT ENABLE

FILTER TIMING

TOEH is measured from the rising edge of the demodulator

output to the first falling edge. The pulse width must fall

within TOEH

≤ t ≤ TOET.

TOEL is measured from the falling edge of the

demodulator output to the rising edge of the next pulse.

The pulse width must fall within TOEL

≤ t ≤ TOET.

TOET is measured from rising edge to the next rising

edge (i.e., the sum of TOEH and TOEL). The pulse width

must be t

≤ TOET. If the Configuration Register 0

(Register 11-1), OEL<8:7> is set to ‘00’, then TOEH

must not exceed TOET and TOEL must not exceed

TINACT.

The filter will reset, requiring a complete new successive

high and low period to enable LFDATA, under the

following conditions.

• The received high is not greater than the

configured minimum TOEH value.

•During TOEH, a loss of signal > 56

μs. A loss of

signal < 56

μs may or may not cause a filter

Reset.

• The received low is not greater than the

configured minimum TOEL value.

• The received sequence exceeds the maximum

TOET value:

-TOEH + TOEL > TOET

-or TOEH > TOET

-or TOEL > TOET

• A Soft Reset SPI command is received.

If the filter resets due to a long high (TOEH > TOET), the

high-pulse timer will not begin timing again until after a

gap of TE and another low-to-high transition occurs on

the demodulator output.

Disabling the output enable filter disables the TOEH and

TOEL requirement and the AFE passes all received LF

data. See Figure 11-10, Figure 11-11 and Figure 11-12

for examples.

When viewed from an application perspective, from the

pin input, the actual output enable filter timing must fac-

tor in the analog delays in the input path (such as

demodulator charge and discharge times).

• TOEH - TDR + TDF

• TOEL + TDR - TDF

The output enable filter starts immediately after TGAP,

the gap after AGC stabilization period.

11.16 Input Sensitivity Control

The AFE is designed to have typical input sensitivity of

3mVPP. This means any input signal with amplitude

greater than 3 mVPP can be detected. The AFE’s internal

AGC loop regulates the detecting signal amplitude when

the input level is greater than approximately 20 mVPP.

This signal amplitude is called “AGC-active level”. The

AGC loop regulates the input voltage so that the input

signal amplitude range will be kept within the linear range

of the detection circuits without saturation. The AGC

Active Status bit (AGCACT<5>) in the AFE Status

regulates the input voltage.

Table 11-2 shows the input sensitivity comparison when

the AGCSIG option is used. When AGCSIG option bit is

set, the demodulated output is available only when the

AGC loop is active (see Table 11-1). The AFE has also

input sensitivity reduction options per each channel. The

Configuration Register 3 (Register 11-4), Configuration

(Register 11-6) have the option to reduce the channel

gains from 0 dB to approximately -30 dB.

OEH

<1:0>

OEL

<1:0>

TOEH

(ms)

TOEL

(ms)

TOET

(ms)

Filter Disabled

Note 1:

Typical at room temperature and

VDD = 3.0V, 32 kHz oscillator.

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