National CP3BT26 manual 15.3 LMX5251 POWER-UP Sequence, 15.4 LMX5252 POWER-UP Sequence

CP3BT26

15.3LMX5251 POWER-UP SEQUENCE

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.

15.4LMX5252 POWER-UP SEQUENCE

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).

Any State

RESET# = Low or

Power is cycled

VDDLMX5251

VCCCP3000 IOVCCCP3000

RESET#LMX5251

RESETCP3000

RFCE

BBCLK

RFDATA

RFSYNC

SDAT

SCLK

SLE

tPTOR

Low High

Low

High

Low

Low

Low

LMX5251	CP3000 LMX5251	Standby	Active
Oscillator	Initialization Initialization
Start-Up

	Off			Any State
				After RF Init
		RESET# = High and			RFCE = Low
		Power is On
Wait for
Crystal Osc.	Power-Up			Sleep
To Stabilize
		Crystal Osc. Stable			RFCE = High
RFCE = High			Wait for
RFDATA = Don't Care	RF Init		Crystal Osc.	Wait XTL
Write Registers			To Stabilize

Crystal Osc. Stable

Idle

LMX5251 in	LMX5251 in Normal Mode
Power-Up Mode	DS016

Figure 20. LMX5251 Power-Up Sequence

DS324

Figure 21. LMX5252 Power States

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

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