User Guide

NPL-4/5
System Module and User Interface Nokia Customer Care
Page 52 Copyright © 2004 Nokia Corporation. All rights reserved. Issue 1 05/04
Main features
The ASIC supports three magnetometer axis. The ASIC features are:
• Pre-amplifier followed by a single-shot sigma delta type of ADC for each measurement
channel
• H-bridge for driving the SET/RESET coil inside the magnetometer element
• Internal voltage reference for the ADC and the magnetometer bridge
• Digital control interfaces (I2C, CBUS, UART)
• Control registers
• One-bit digital control output signal to turn on/off the external linear regulator
Block diagram and functional descriptions
Figure 20: Block Diagram
The magnetometer interface has three differential inputs for X-, Y- and Z-bridge respec-
tively. The measurement path for each axis can be enabled/disabled separately and the
power consumption of any unused path is minimized. The magneto-resistive bridges of
all axes are biased by a single reference voltage (2.2 V) provided by the internal band-
gap reference.
I2C slave interface
write cmd,addr
write data (8)
read addr
read data (8)
CBUS interface
UART interface
write cmd,addr
write data (16)
read addr
read data (16)
write cmd,addr
write data (8)
read addr
read data (8)
CBusClk
CBusEnX
CBusDa
UARTRx
CLOCK
DIVIDER
internal
clocks
Pre - amplifier
Magnetometer
SET/RESET
generator
Clk
Single shot
measurement
counters
Sigma-delta ADC
Pre
- amplifier
Pre - amplifier
data
REGISTERS CONTROL
reset
ClrX
Sigma-delta ADC
Sigma-delta ADC
Bandgap
reference
UARTTx
VBridge
I2CClk
I2CDa
InX
InY
InZ
2
2
2
3
3
2
2
SRVdd
SROp
SROm
TankCharge
SRVss
RegCtrl
SMC
TMC
DTest1
DTest2
DTest3
DVdd
DVss
A
Vdd
A
Vss