Bluetooth/Gps Circuit - Kenwood NX-5400 Service Manual

2.4.9 Bluetooth/GPS Circuit

The main component of the Bluetooth/GPS circuit is BT/GPS IC (IC850).
The clocks of BT/GPS IC require 19.2MHz for core and 32.768kHz slow clock (X850) for UART.
19.2MHz clock (X700) is shared with MPU/DSP (IC702), and is supplied through the clock buffer IC (IC700).
The BT/GPS IC communicates to the MPU/DSP (IC702) on the HCI UART. Interface of UART & Digital audio (PCM) between the
MPU/DSP (IC702) and the BT/GPS IC (IC850), have level conversion at the level shift IC (IC852, IC853).
The BT/GPS IC is powered by 1.8V and 3.3V which are supplied from two discrete external regulators (IC38 and IC37). The input of
these regulators is sourced from a switching regulator (IC33) which regulates the battery voltage to 3.8V.
GPS antenna
Matching
HPF
BT antenna
2.4.9.1 Bluetooth Circuit
The BT/GPS IC (IC850) support Bluetooth 3.0 up to HCI level.
The TX/RX frequency is 2400-2483.5MHz (79ch Hopping, 2402-2480MHz, 1MHz step). The transmit power is +2dBm at Bluetooth
antenna input.
The Bluetooth antenna is made of sheet metal, and connected to the BT/GPS IC (IC850) through the LC filter (L855).
Frequency configuration for Bluetooth is following:
There are two LO modes: 2X and Offset LO (OSLO). 2X where LO is 2*RF_FREQ (e.g. when transmitting at 2441MHz it is at
4882MHz). OSLO where LO is at 2/3*RF_FREQ (e.g. when transmitting at 2441MHz it is at 1627.333MHz).
In RX the 2X is always used.
In GFSK TX if power is 10dBm or more then OSLO is used.
In EDR2 TX if power is -12dBm or more then OSLO is used.
In EDR3 TX if power is -12dBm or more then OSLO is used.
Otherwise 2X is used for TX as well.
LNA Supply
LNA Enable
Pre-SAW LNA Attenuator
TCXO
19.2MHz
LC filter
Fig.5 Bluetooth/GPS circuit
Fig.6 Bluetooth circuit
IC850 BT/GPS IC
VDD_TCXO(G1) VBAT1(A2)
TCXO_LDO_IN(H1)
GPS_EXT_LNA_EN(H6)
GPS IC(IC850)
GPS_LNA_IN(L2)
BT_HCI_UART_TX(A4)
Post-SAW
BT_HCI_UART_RX(B5)
BTFM_nSHUTDOWN(A6)
IC700
GPS PA EN(G3)
Clock
TCXO_CLK_LV(F1)
Buffer
RTC_CLK(H9)
BT_RF
3.3V
1.8V
VDDS
IC702
GPS_TX
LEVEL
GPS_RX
SHIFT
MPU/DSP
OSCILLATOR
32.768kHz
(No.RA016<Rev.001>)1-17