mc33596 Freescale Semiconductor, Inc, mc33596 Datasheet - Page 22

• Manufacturer Part Number: mc33596
• Description: Pll Tuned Uhf Receiver For Data Transfer Applications
• Manufacturer: Freescale Semiconductor, Inc

Receiver On/Off Control
Each time is defined with the associated value found in the RXONOFF register.
The strobe oscillator is a relaxation oscillator in which an external capacitor C3 is charged by an internal
current source (see
strobe frequency is F
In receive mode, setting the STROBE pin to V
the oscillator threshold voltage, the condition on which the STROBE pin is set to V
internally, and the oscillator pulldown circuitry is disabled. This limits the current consumption. After a
strobe forced at “1”, the external driver should pass via a “0” state to discharge the capacitor before going
to high impedance state (otherwise, the ON time would last a long time after the driver release).
When the strobe oscillator is running (i.e., during an off time), forcing the STROBE pin to V
strobe clock and, therefore, maintains the circuit off.
Figure 13
22
•
•
•
•
STROBE
STROBE
Off time is clocked by the strobe oscillator,
On time is clocked by the crystal oscillator, enabling accurate control of the on time and,
therefore, the current consumption of the whole system.
On time = RON[3:0] x 512 x T
Off time = receiver OFF time = N x T
from ROFF[2:0] (see
Receiver
Counter
Counter
Status
Digital
Clock
Clock
shows the associated timings.
Off
On
Threshold
0
RON
Figure
Strobe
43). When the threshold is reached, C3 is discharged and the cycle restarts. The
= 1/T
Off
Table
Cycling Period
0
t
Strobe
Strobe
ROFF-1 ROFF
Figure 13. Receiver On/Off Sequence
18).
with T
digclk
MC33596 Data Sheet, Rev. 3
(see
Strobe
Strobe
On
CCIO
Crystal Oscillator Startup
0
Table
= 10
RON
+ MIN (T
at any time forces the circuit on. As V
17; begins after the crystal oscillator has started),
6
x C3.
Off
0
Strobe
/ 2, receiver On time), with N decoded
SET TO V
STROBE
RON
On
CCIO
CCIO
Freescale Semiconductor
is detected
CCIO
GND
is above
stops the