UR7HCPXZ-S440 Datasheet, PDF (3/10 Pages) Semtech Corporation – Advanced “Click-to-Select” No-DriftTM Pointing Stick Controller

FUNCTIONAL DESCRIPTION
The UR7HCPXZ-S440 consists
functionally of four major sections
(see Functional Diagram, previous
page). These are the PixiPoint^TM Z
Interface, the 16-Bit Timer, the
Oscillator Circuit and the Serial
Communication Port. All sections
communicate with each other and
operate concurrently.
SIGNAL CONDITIONING CIRCUIT
The PixiPoint^TM Z sensor is a
flexible (but very firm) “beam” with
four Strain Gauges – one on each
of the sides. If force is applied
precisely in the X direction, then it
will produce a change of resistance
of only the two X gauges. Force in
the Y direction will cause changes
only in the Y gauges. One of the
pair of the gauges will increase,
while the other will concurrently
decrease in resistance.
If the user presses on the sensor
from the top (Z-Axis), all of the
strain gauges will decrease the
resistance.
When a test current is passed
through the gauges, these
resistance changes are converted
into the voltage changes. These
signals are very small, typically
under 1 mV Full Scale.
The patented Signal Conditioning
Circuit balances and amplifies the
incoming signals for digitizing by a
built-in A/D converter.
PIN DEFINITIONS
Mnemonic
VDD
VSS
VSS2
OSCIN
Pin #
8
11
7
9
_OSCOUT
10
_RESET
6
RTS
26
TXD
27
_LB
18
_MB
19
_SB
20
_RB
21
DRV_XY0
12
DRV_XY1
13
Z_SIG0
14
Z_SIG1
15
DRVZ
4
SELX
2
SELZ
3
INH
22
VREF
5
AD
1
DA
31
OFST
32
SP0
23
SP1
24
SP2
25
SP3
28
SP4
29
SP5
30
SENSOR_SEL 17
ZTAP_EN
16
Type
P
P
P
I
O
I
I
I
I/O (nd)
I/O (nd)
I/O (nd)
I/O (nd)
I/O
I/O
I/O
I/O
I/O
O
O
O
AI
AI
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O(nd)
I/O(nd)
Name and Function
Power Supply: +5V
Ground
Ground
Oscillator Input: external clock input or one
side of the Ceramic Resonator with built-in Load
Capacitors
Oscillator Output: open for external clock
input or other side of the Ceramic Resonator with
built-in Load Capacitors
Reset: apply 0V to provide orderly start-up
Request to Send: High = Disable TX
Transmit to Host: Idle High
Left Button: active low, strobed sampling
Middle Button: active low, strobed sampling
Scroll Button: active low, strobed sampling
Right Button: active low, strobed sampling
Sensor’s Excitation Driver
Sensor’s Excitation Driver: connect to DRV_XY0
Sensor’s Excitation Driver
Sensor’s Excitation Driver: connect to Z_SIG0
Sensor’s Excitation Driver
Select X: control line for analog multiplexer
Select Z: control line for analog multiplexer
Multiplexer Inhibit Signal: active high
Reference Voltage for built-in A/D
Analog to Digital Converter Input
Digital to Analog Converter Output
Offset: resets the offset circuit during inactivity
Switched Power Driver
Switched Power Driver: connect to SP0
Switched Power Driver: connect to SP0
Switched Power Driver: connect to SP0
Switched Power Driver: connect to SP0
Switched Power Driver: connect to SP0
Sensor Select Pin: Float - CTS, Low - Bokum
ZTAP Z Enable Pin: Float - Enabled, Low - Disable
Note: An underscore before a pin mnemonic denotes an active low signal. For SENSOR_SEL
and ZTAP_EN Pins: Upon power-up they are inputs with pull-up. After initialization, the chip
will switch the pull-ups off and drive these pins low. Selection of a particular mode is made
by connecting the pin to ground or leaving it not connected (floating).
Pin Types Legend: AI=Analog Input; I=Input; O=Output; I/O=Input or Output;
I/O (nd)=Input or Output with N-channel Open Drain driver
SIGNAL CONDITIONING CIRCUIT (CON’T)
Semtech’s proprietary circuit can correct a significant imbalance between
the gauges in each X and Y pair (+/- 25%), allowing relaxed manufacturing
tolerances for the sensors, interconnecting cabling, and temperature-shift
induced errors (no performance degradation over the full operating
temperature range and for large temperature gradients between the
paired gauges).
Copyright ©1999-2001 Semtech Corporation
3
DOC7-PXZ-S440-DS-103
www.semtech.com