beautypg.com

Polling current calculation – Rainbow Electronics ATA5746 User Manual

Page 26

background image

26

4596A–RKE–05/06

ATA5745/ATA5746 [Preliminary]

8.

Polling Current Calculation

Figure 8-1.

Polling Cycle

In an RKE and TPM system, the average chip current in Polling mode, I

Polling

, is an important

parameter. The polling period must be controlled by the connected microcontroller via the pins
ENABLE and RX. The polling current can be calculated as follows:

I

Polling

= (T

Startup_PLL

/ T

Polling_Period

)

× I

Startup_PLL

+ (T

Startup_Sig_Proc

/ T

Polling_Period

)

× I

Active

+

(T

Bitcheck

/ T

Polling_Period

)

× I

Active

+ (T

Polling_Period

– T

Startup_PLL

– T

Startup_Sig_Proc

– T

Bitcheck

) /

T

Polling_Period

× I

Standby

T

Startup_PLL

:

depends on 315 MHz/433.92 MHz application.

T

Startup_Sig_Proc

:

depends on 315 MHz/433.92 MHz application and the selected bit
rate range.

T

Bitcheck

:

depends on the signal bit rate (1 / Signal_Bit_Rate).

T

Polling_Period

:

depends on the transmitter telegram (preburst).

I

Startup_PLL

:

depends on 3V or 5V application and the setting of pin CLK_OUT.

I

Active

:

depends on 3V or 5V application, ASK or FSK mode and the setting of
pin CLK_OUT.

I

Standby

:

depends on 3V or 5V application and the setting of pin CLK_OUT.

Example:-

315-MHz application (ATA5746), bit rate: 9.6 Kbits/s, T

Polling_Period

= 8 ms

--> T

Startup_PLL

=

269 µs

--> T

Startup_Sig_Proc

=

324 µs

(Bit Rate Range 3)

--> T

Bitcheck

=

104 µs

3V application; ASK mode, CLK_OUT disabled
--> I

Startup_PLL

=

4.5 mA

--> I

Active

=

6.5 mA

--> I

Standby

=

0.05 mA

--> I

Polling

= 0.545 mA

I

Standby

I

Standby

I

Active

I

Star

tup_PLL

I

Active

I

Star

tup_PLL

RX

I

Supply

ENABLE

T

Bitcheck

(= 1 / Signal_Bitrate (average)

T

Startup_PLL

(Startup RF-PLL)

T

Startup_Sig_Proc

(Startup Signal Processing)