BU21008MUV

Technical Note

3/16

www.rohm.com

2009.04 - Rev.B

© 2009 ROHM Co., Ltd. All rights reserved.

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Block Diagram, Pin configuration

AVDD

DVDD

SREF

SIN[15:0]

CS

SCL

SDA/TXD

RXD

SDN

CLK_EXT

INT

MODE[1:0]

Sensor I/F、

CV translate

circuit

ADC

Data register

Conversion

sequence control

host I/F

Power

management

Clock

generation

CR

oscill

ation

Reset

generation

Power

on

Reset

Data correction and

making to format

DVSS

AVSS

DVSS

DVDD

AVDD

SREF

SIN[0]

SIN[1]/LED[0]

SIN[2]

MODE[1]

MODE[0]

AVSS

TSTA

SIN[15]/LED[7]

SIN[4]

SIN[13]/LED[6]

SIN[12]

SIN[13]/LED[6]

SIN[3]/LED[1]

・

Sensor I/F CV translate circuit

This module selects between sensor inputs. The selection sequences between all 16 channels.

・

AD Conversion

The voltage into which CV is converted is converted into a digital value.

Conversion is 10 bit and full scale corresponds to AVDD.

・

Conversion sequence control

Performs timing generation for the analogue circuitry and a sequencer circuit for selection of the sensor channel for

conversion.

・

Data correction and making to format

This module provides the digital intelligence of the sensor.

The block includes, amongst other things, scaling, adding offsets and input filtering for de-bouncing.

Registers are formatted to simplify usage by the software application.

The block implements auto-calibration to manage drift in temperature, process variation, voltage variation and aging

effects.

・

Data register

This stores the results for the software application. Please refer to the register map for details.

・

HOST I/F

2 wire serial interface.

・

Power management

The power management block provides smart power control.

When the sensors are not in use, the Controller automatically transitions into a low-power mode.

When a sensor is touched, then the device automatically wakes up and enters its normal operation.

The chip drives an INT pin for alerting the controller device in this case.

・

Reset generation

The circuit is initialized by a either a soft reset command or by the external SDN pin.

・

Clock generation

The device has an internal oscillator.

Provision is also made if the application would like to make use of an external clock input.