National CP3BT26 Manuale Utente

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To power-up a Bluetooth system based on the CP3BT26
and LMX5251 devices, the following sequence must be per-
formed:

1. Apply VDD to the LMX5251.
2. Apply IOVCC and VCC to the CP3BT26.
3. Drive the RESET# pin of the LMX5251 high a minimum

of 2 ms after the LMX5251 and CP3000 supply rails are
powered up. This resets the LMX5251 and CP3BT26.

4. After internal Power-On Reset (POR) of the CP3BT26,

the RFDATA pin is driven high. The RFCE, RFSYNC,
and SDAT pins are in TRI-STATE mode. Internal pull-
up/pull-down resistors on the CCB_CLOCK (SCLK),
CCB_DATA (SDAT), CCB_LATCH (SLE), and
TX_RX_SYNC (RFSYNC) inputs of the LMX5251 pull
these signals to states required during the power-up
sequence.

5. When the RFDATA pin is driven high, the LMX5251 en-

ables its oscillator. After an oscillator start-up delay, the
LMX5251 drives a stable 12-MHz BBP_CLOCK
(BBCLK) to the CP3BT26.

6. The Bluetooth baseband processor on the CP3BT26

now directly controls the RF interface pins and drives
the logic levels required during the power-up phase.
When the RFCE pin is driven high, the LMX5251
switches from “power-up” to “normal” mode and dis-
ables the internal pull-up/pull-down resistors on its RF
interface inputs.

7. In “normal” mode, the oscillator of the LMX5251 is con-

trolled by the RFCE signal. Driving RFCE high enables
the oscillator, and the LMX5251 drives its BBP_CLOCK
(BBCLK) output.

A Bluetooth system based on the CP3BT26 and LMX5252
devices has the following states:

„ Off—When the LMX5252 enters Off mode, all configura-

tion data is lost. In this state, the LMX5252 drives BPOR
low.

„ Power-Up—When the power supply is on and the

LMX5252 RESET# input is high, the LMX5252 starts up
its crystal oscillator and enters Power-Up mode. After the
crystal oscillator is settled, the LMX5252 sends four
clock cycles on BRCLK (BBCLK) before driving BPOR
high.

„ RF Init—The baseband controller on the CP3BT26 now

drives RFCE high and takes control of the crystal oscilla-
tor. The baseband performs all the needed initialization
(such as writing the registers in the LMX5252 and crystal
oscillator trim).

„ Idle—The baseband controller on the CP3BT26 drives

RFDATA low when the initialization is ready. The
LMX5252 is now ready to start transmitting, receiving, or
enter Sleep mode.

„ Sleep—The LMX5252 can be forced into Sleep mode at

any time by driving RFCE low. All configuration settings
are kept, only the Bluetooth low power clock is running
(B3k2).

„ Wait XTL—When RFCE goes high, the crystal oscillator

becomes operational. When it is stable, the LMX5252
enters Idle mode and drives BRCLK (BBCLK).

The power-up sequence for a Bluetooth system based on
the CP3BT26 and LMX5252 devices is shown in Figure 22.

VDD

LMX5251

RFCE

BBCLK

RFDATA

RFSYNC

VCC

CP3000

IOVCC

CP3000

Low

Low

High

Low

SDAT

Low

SCLK

Low

SLE

Standby

LMX5251 in Normal Mode

LMX5251 in

Power-Up Mode

LMX5251

Oscillator

Start-Up

LMX5251

Initialization

CP3000

Initialization

Active

High

DS016

RESET#

LMX5251

RESET

CP3000

t

PTOR

Idle

DS324

Crystal Osc. Stable

RF Init

RFCE = High

RFDATA = Don't Care

Write Registers

RESET# = High and
Power is On

Power-Up

Wait for

Crystal Osc.

To Stabilize

RESET# = Low or
Power is cycled

Off

RFCE = High

Wait XTL

Wait for

Crystal Osc.

To Stabilize

RFCE = Low

Sleep

Any State

Any State

After RF Init

Crystal Osc. Stable