Infineon FingerTIP FTF 1100 MF1 User manual

Microsystems for Biometrics
FingerTIP™
FTF 1100 MF1 V2.0
CMOS Chip and System
Data Book 3.3 (Status: 05.00)
This document contains information on a new product. Details are subject to change
without notice.

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Contents
1 INTRODUCTION 5
1.1 Validity of the Manual 5
1.2 Revision History 5
1.3 Related Documentation 5
2 OVERVIEW 6
2.1 Features of the FingerTIP™=6
2.2 Functional Block Diagram of the FingerTIP™ 7
2.3 Dynamics of the Sensor 8
2.4 Fingerprint Image Readout 10
2.5 Sleep Mode 11
2.6 Selecting EPP 1.9 or SPI Mode 11
2.7 Switch-on Sequence of the FingerTIP™ 11
2.8 Defect Rate 11
3 THE PARALLEL INTERFACE EPP 1.9 12
3.1 Basic Information on the Parallel Interface 12
3.2 EPP Register Definitions 13
3.3 EPP 1.9 Signal Definitions 13
3.4 Timing of the EPP 1.9 Protocol Used by the FingerTIP™ 14
3.5 Selecting the EPP Mode 15
3.6 Resetting the Pixel Pointer and Changing the Dynamics in EPP Mode 15
3.7 Set the FingerTIP™ into Sleep Mode in EPP Mode 15
3.8 Fingerprint Image Readout 16
3.9 Pinout of the FingerTIP™ in EPP Mode 17
3.10Recommended Electrical Connection of the FingerTIP™ in EPP Mode 19
4 THE SERIAL INTERFACE SPI 20
4.1 Basic Information on the Serial Interface SPI 20
4.2 Pin Description of the SPI Interface 21
4.2.1 EPP/SPI 21

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4.2.2 Chip Select (/CS) 21
4.2.3 Serial Input (SI) 21
4.2.4 Serial Output (SO) 22
4.2.5 Serial Clock (SCK) 22
4.3 SPI Protocol and Timing 23
4.4 The FingerTIP™ SPI Commands 25
4.4.1 Command: Set Mode 26
4.4.2 Command: Reset Pointer 26
4.4.3 Command: Read Status 27
4.4.4 Command: Read Data 27
4.5 Fingerprint Image Readout 28
4.6 Pinout of the FingerTIP™ in SPI Mode 29
4.7 Recommended Electrical Connection of the FingerTIP™ in SPI Mode 31
5 ELECTRICAL CHARACTERISTICS AND PIN DESCRIPTION 32
5.1 FingerTIP™ Electrical Characteristics 32
5.2 Static Pad Characteristics 33
5.3 Pin Description 34
6 MODULE 35
6.1 Module Dimensions and Material 35
7 FINGERTIP™ SDK SOFTWARE AND BIOMETRIC ALGORITHMS 36
7.1 Enrollment 36
7.2 Verification 36
8 LITERATURE 37
9 INDEX 38

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1 Introduction
This document describes the FingerTIP™ and its features. Chapter 2 describes the
function of the FingerTIP™. The following chapters explain the EPP and SPI interface of
the sensor and its timing characteristics. Chapter 5 outlines the electrical characteristics.
The module dimensions are shown in chapter 6. The last chapter contains general
information on the SDK software package for fingerprint recognition available from Infineon
Technologies.
1.1 Validity of the Manual
This FingerTIP™ Data Book is valid for sensor devices FTF 1100 MF1.
1.2 Revision History
Date Revision
04.00 3.3 Added revision history
Changed ESD references from 8kV to 12kV maximum
Added section 3.10 Recommended connection in EPP mode
Added section 4.7 Recommended connection in SPI mode
Changed section 2.1 to reference enhanced sensor surface process
1.3 Related Documentation
The Design-In Guideline /2/ of the FingerTIP™ contains information on the electrical and
mechanical design-in and describes for example how to minimize the influence of ESD air
discharge. We strongly recommend reference to this document in your design for
precautionary measures and attributes.

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2 Overview
The FingerTIP™ is available as a module. The module consists of the sensor chip in a
plastic package with a metal frame and a flexible PCB (Printed Circuit Board). Biometric
algorithms are also available on request.
2.1 Features of the FingerTIP™=
==
=
Measuring technique capacitive sensor in CMOS technology
Resolution 224 x 288 pixels (513 dpi); data format: 8 bit/pixel
Image capture and < 100ms (in EPP mode @ VCC = 4.5V – 5.5V; T = 25°C)
readout time1< 110ms (in SPI mode @ VCC = 4.5V – 5.5V; T = 25°C)
< 140ms (in SPI mode @ VCC = 3.3V – 4.5V; T = 25°C)
Usable gray levels (dynamics) approx. 70 or approx. 40 (programmable)
Interface parallel interface ≤1MHz (EPP 1.9 protocol)
serial interface (SPI ≤5MHz [VCC = 4.5V – 5.5V]
res. ≤4MHz [VCC = 3.3V – 4.5V])
Supply voltage EPP: VCC = 4.5V – 5.5V
SPI: VCC = 3.3V – 5.5V
Power consumption EPP: < 5mW / typ. 50mW (sleep/readout mode, 1MHz, VCC=5V)
SPI: < 5mW / typ. 50mW (sleep/readout mode, 5MHz, VCC=5V)
ESD protection212kV air discharge on the sensor surface
Mechanical resistance3ultra hard surface provides protection against ´ruboff´ and
scratches on the sensor surface
Chemical resistance3Enhanced resistance against most liquids, gases and sweat
with advanced surface fabrication process
Size sensor area: 11.1mm x 14.3mm
module: 21.0mm x 18.0mm x 1.5mm, flexible PCB: 45.9mm
Module package PPS plastic housing with metal frame and a PI PCB
interconnect (meets flammability standard UL94V0)
Module connector flexible 21-wire PCB with 0.5 mm pitch
Life cycle > 100,000 tips
> 0.8 years readout mode, 3 years sleep mode and 10 years
storage
Operating temperature - 40°C < T < +85°C (non condensing)
Storage temperature - 40°C < T < +125°C (non condensing)
1The total system reaction time would including the image capture and readout time as well as fingerprint identification. Therefore this
time depends mainly on the processor performance, the algorithms used for identification and the image capture speed. With the
Infineon FingerTIP™ SDK running on an 400MHz PC this time is usually less than 500ms.
2This value is guaranteed only for the FingerTIP™ module if the notes of the Design-In Guideline are observed.
3Details see qualification report.

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2.2 Functional Block Diagram of the FingerTIP™
The block diagram (figure 1) shows the structure of the FingerTIP™. The sensor surface
is made of an environmental resistant material that protects a matrix of 224 x 288 metal
electrode pixels. The measurement technology used is capacitive and outputs an 8-bit
value per pixel.
Figure 2 illustrates the capacitive measurement technology: The capacitance CPis formed
by a single metal electrode (pixel) and the finger that constitutes the second electrode.
Valleys and ridges on the finger will yield varying CPvalues. CPis too small for direct
measurement, therefore CPis measured indirectly. CPis charged (SW1 is closed and SW2
is open) and discharged (SW1 is open and SW2 is closed) up to 255 times. The voltage of
CCincreases with each charge cycle. The charge stored in CPis proportional to the
capacitance of CP.
The voltage of CCis compared with the reference voltage Vref. If both values are equal, the
value of the 8-bit counter, which counts the number of charge cycles, is stored and the
charge cycle ends. This value represents the gray level of the pixel of a fingerprint. Two
values of Vref can be selected to allow different ranges of usable gray levels (section 2.3).
Figure 1: Functional Block Diagram FingerTIP™
DATA
switch
8
8DATA
OUT
1. pixel of 1. line
224. pixel of 1. line
parallel
data
select
EPP or SPI
output
serial
data
EPP/SPI /RESET /REQUEST READY SI SCK /CS
(EPP) (EPP) (EPP) (SPI) (SPI) (SPI)
parallel
/
serial
converter
sensor cell array
288 lines x 224 columns

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+
-
SW1 SW 2
integrating
ca
p
acito
r
finger
surface
comparator
Cp
Vref
Cc
V
CC $00 ... $FF
COUNTER
STOP
Figure 2: FingerTIP™: Capacitive Measurement Technique
In each charge cycle one line with 224 pixels is acquired. These 224 8-bit values are first
stored in the line register. In a second step the data is transferred to the shift register. The
output lines of the shift register are connected to the data switch and the parallel to serial
converter. Depending on the selected mode – EPP or SPI – the DATA switch unit
connects the corresponding input line to the output line (EPP: parallel output, SPI: serial
output). While the values are being transferred from the shift register to the output unit, the
next line is evaluated. Once the shift register has output all the 224 bytes, a 225th byte with
the value 00h is added to signal the line end. When all the lines are output the FingerTIP™
continues to output a sequence of 225 bytes (224 x FFh and 1 x 00h).
2.3 Dynamics of the Sensor
The FingerTIP™ provides an 8-bit representation of the gray levels for each pixel. In terms
of image processing, the value 0 represents black and the value 255 white. In reality, the
gray level representation of a fingerprint will be limited by the so called water line and air
line as shown in the schematic histogram (figure 3).
Figure 3: Schematic Histogram of the FingerTIP™
frequency of
occurrence
air line
(finger valley)
water line
(finger ridge)
D
y
namics of the Sensor

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Figure 4: The Corresponding Sum-Histogram
The maximum obtainable local contrast is determined by the maximum difference between
the gray levels of finger valleys (air) and finger ridges (skin moisture). This local contrast is
called dynamics.
An alternative representation of the gray levels is the so-called sum-histogram, which is
generated from the fingerprint histogram (shown in figure 3) by integration over all gray
levels. A diagram of the sum-histogram is shown in figure 4.
The so-called water line appears when the sensor surface is covered with water. If the
surface is in contact with air, the air line appears. A typical fingerprint will be somewhere
between these two characteristic lines and is illustrated in figure 4.
The dynamics of the sensor depends on the internal reference voltage Vref (figure 2). Two
values of Vref are selectable to allow the sensor to be adapted to different requirements.
Table 1 shows the number of usable gray levels. The procedure to change the dynamics
is shown in section 3.6 for EPP mode and section 4.41 for SPI mode.
High dynamics Low dynamicsSupply voltage VCC
Vref usable gray levels Vref usable gray levels
5.0 V 3.6 V approx. 70 2.5 V approx. 40
Table 1: Reference Voltages and the Resulting Values for Dynamics
typicalfingerprint
"air line”
(sensor surface
in contact with air) gray level
Sum of
frequencies
of occurrence
255
0
"water line”
(sensor surface
covered with water)
wate
r
(finger ridge) air (finger valley)

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Figure 5: Pixel Position on the FingerTIP™
2.4 Fingerprint Image Readout
The fingerprint image consists of 288 x 224 pixels. Each pixel is represented by an 8-bit
value. Figure 5 shows the position of pixel (1,1) and the definition of lines and columns in
the sensor field. When the readout is started (see chapter 3 and 4 for details), the image is
transferred line by line starting with the first line. Each line is read out byte by byte (a pixel
is represented by one byte) starting with pixel 1. An extra byte with the value 00h is added
to each line, signaling the end of the line. This byte is called LineEndMark. Once the whole
image is read out, the FingerTIP™ continuously outputs a sequence of 225 bytes (224 x
FFh and 1 x 00h). The complete procedure for resetting the pixel pointer and reading out
the image is explained in chapters 3 and 4.
It is recommended to check the LineEndMark after every line read. Chapters 3 and 4 gives
some hints for a failure analysis.
PCB
(Pixel Pointer
reset position)
1. pixel of 1. line
1. pixel of 288. line
224. pixel of 1. line
Sensor cell array
288 line x 224 columns
line
column
1. column

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2.5 Sleep Mode
The FingerTIP™ offers a power saving mode called sleep mode. In this mode the power
consumption of the sensor is reduced to about 10% of the power consumption in readout
mode (chapter 5.1, table 13). The life time of the sensor will be extended if it is switched to
this mode (see section 2.1). Therefore it is recommended to switch the sensor to sleep
mode whenever no readout of an image is necessary. When the sensor is switched back
to readout mode, a new fingerprint can be acquired immediately. Section 3.7 (for EPP) and
section 4.4 (for SPI) explain how to switch the sensor to sleep mode.
2.6 Selecting EPP 1.9 or SPI Mode
The EPP/SPI input pin of the FingerTIP™ is used for selecting the EPP 1.9 or SPI mode.
Before power-on, the EPP/SPI pin must be set to GND to select SPI mode. Accordingly,
the EPP/SPI pin must be set to VCC to select EPP 1.9 mode by using a pull-up resistor.
The mode can not be changed after power-on. Therefore the logic level of this input must
not be changed over the time of power on.
2.7 Switch-on Sequence of the FingerTIP™
The FingerTIP™ has a built-in power-on reset. Therefore no external reset signal is
needed for a sensor reset. The RESET pin of the FingerTIP™ is only active in EPP mode
and is needed for resetting the pixel pointer of the sensor cell field to pixel position (1,1)
and for changing the dynamics.
2.8 Defect Rate
Usually all biometric software including our FingerTIP™ Software Package can handle line
and column defects of captured fingerprints. Up to three line or column defects and up to
50 single pixel defects are allowed in the cell field of the FingerTIP™.

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3 The Parallel Interface EPP 1.9
This chapter describes the parallel interface of the FingerTIP™ and how to read out an
image, change the dynamics and set sleep mode. First the data transfer protocol, electrical
and timing parameters of the sensor's EPP mode, which is compatible to the IEEE 1284
standard, is described. Next the readout procedure will be explained using a block
diagram. Finally, the pinout of the sensor's parallel port is shown.
For further information for design-in the sensor, please refer to the Design-In Guideline /2/.
3.1 Basic Information on the Parallel Interface
The FingerTIP™ offers an EPP 1.9 compatible parallel interface according to the IEEE
1284 standard. The IEEE 1284 defines five different data transfer modes: Standard Mode
(SPP), Nibble Mode, Byte Mode, Extended Capabilities Port Mode (ECP) and Enhanced
Parallel Port Mode (EPP). Only the ECP and EPP modes use a hardware-implemented
handshake for data transfer. This leads to high data rates of at least 1MByte/s. The
FingerTIP™ has an EPP 1.9 compatible interface which is easy to implement on the PC
side and which can easily be emulated by a microcontroller/processor. Please note that
the older version EPP 1.7, which does not meet the IEEE 1284 standard, is not supported
by the FingerTIP™.
If not already done, the EPP 1.9 mode can be enabled on the PC by entering the BIOS
setup menu or by using a BIOS setup utility program. The FingerTIP™ cannot be used on
printer ports which do not support EPP 1.9.
The sensor represents a level-two EPP device, which is designed for high data rates
according to IEEE 1284.
The IEEE 1284 standard specifies four different modes for EPP 1.9: Read data, write data,
write address and read address. The FingerTIP™ only supports the read data cycle.
Therefore the sensor uses only two handshake lines (nDataStrb/REQUEST and
nWait/READY) and 8 data lines. An additional line (nReset/RESET) is used for resetting
the sensor's pixel pointer, selecting the sleep mode and for changing the dynamics. The
following sections describe the timing, signal definition and protocol.
More background information on the EPP parallel port protocol can be found, for example,
in the book Parallel Port Complete /3/

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3.2 EPP Register Definitions
The PC printer port uses five I/O addresses in EPP mode. As the EPP can emulate an
SPP the first three addresses 0,1 and 2 (offset to the base_address of the printer port, for
example 378h for LPT1) are used by SPP. The addresses 3 and 4 are used by the EPP.
As the FingerTIP™ only supports read cycles, address 4 is needed. By executing a single
I/O read instruction on [base_address + 4], the PC EPP controller will generate the
necessary handshake signals to transfer one data byte from the sensor to the PC. For
more information please refer to the Design-In Guideline /2/.
3.3 EPP 1.9 Signal Definitions
Table 2 describes the EPP signals and shows their corresponding SPP signals used by
the FingerTIP™.
FingerTIP Signal SPP Signal EPP Signal Direction Description
/RESET nInit nReset PC →FTIP Reset pixel pointer
Activate sleep mode
Change dynamics
/REQUEST nAutoLF nDataStrb PC →FTIP Start read cycle (low active)
READY Busy nWait FTIP →PC Data valid (low active)
DA0-DA7 D1-D8 AD1-AD8 FTIP →PC Data Lines
Vss Ground Ground Ground
Table 2: Signal Definition of the FingerTIP™ (FTIP) in EPP 1.9 Mode
Table 3 shows the EPP pin names and the connection between the FingerTIP™ and the
printer port. Note that a one by one connection of the sensor and the printer port is not
recommended. Some PCs use weak output drivers for the handshake lines. This results in
poor signal quality if long cables are used between sensor and printer port. For more
information please refer to the Design-In Guideline /2/.
FingerTIP Signal Pin No. Sensor SPP Signal Pin No. EPP Port
/RESET 4 nInit 16
/REQUEST 5 nAutoLF 14
READY 6 Busy 11
DA0-DA7 9-16 D1-D8 2-9
Vss 2,19 Ground 18-25
Table 3: Pin Connection Between the FingerTIP™ and the Printer Port

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3.4 Timing of the EPP 1.9 Protocol Used by the FingerTIP™
Figure 6 shows the EPP protocol for a data read cycle and the timing. Table 4 shows the
values of the timing parameters. The pad characteristics are described in chapter 5.
After a reset, which sets the pixel pointer to position (1,1), readout of the first byte can be
started. A readout cycle is started when the /REQUEST line switches to low. The sensor
outputs the data byte and switches the READY line to high if the data is valid. In the next
step the PC reads the data byte and afterwards sets the /REQUEST line to high. Now the
sensor switches the READY line to low and the data lines change to tristate. Now a new
readout cycle can be started. During readout of the image no reset is needed.
tristate
tristate
Cyc
DA0 – DA7
from sensor
READY
from sensor
/REQUEST
from PC
/RESET
from PC
Figure 6: EPP Timing Diagram of the FingerTIP™. I/O Level: TTL Compatible
Interval Name Min. Typ. Max. Dependency [PC or Sensor]
Power-on reset 80 µs
TRst Reset impulse 2 µsReset [PC]
TReq Reset to request 300 µs[PC]
TSData setup time 10 ns 50 ns 100 ns Data setup time [Sensor]
THData hold time 100 ns Data hold time [Sensor]
TRea Request to ready 600 ns 700 ns Response time valid data [Sensor]
TTra Transfer time 200 ns Transfer data to PC [PC]
TES Deadlock time 50 ns 125 ns [Sensor]
TNR Next read 30 ns [Sensor]
TCyc Transfer of 1 Byte ≤1.0 µs [PC / Sensor]
tRO / tFO Output Rise/Fall Time 0.20 V/ns 0.50 V/ns 0.80 V/ns @ CI/O_Line = 50 pF
tRI / tFI Input Rise/Fall Time 0.05 V/ns 0.50 V/ns 0.80 V/ns @ CI/O_Line = 50 pF
Table 4: Timing Parameters; Typical Values for 1MHz EPP Clock Frequency (VCC = 5V)

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3.5 Selecting the EPP Mode
When power is switched on, the EPP/SPI pin must be set to VCC for selecting the EPP
mode. It is recommended to connect the EPP/SPI pin to VCC by using a pull-up resistor. It
is not possible to change from SPI to EPP mode without switching power off and on. If the
sensor is in EPP mode, the EPP/SPI pin must be at high level all the time.
3.6 Resetting the Pixel Pointer and Changing the Dynamics in EPP Mode
In EPP mode the dynamics can only be changed using the /RESET line. Please note that
via the /RESET signal the dynamics can be changed only from low to high but not vice
versa. To change the dynamics to low, the complete image must be read out. After the last
byte of the image has been read out, the sensor resets its internal dynamics register. Now
the dynamics is set to low by default. With the following reset only the pixel pointer is set to
position (1,1) – the dynamics is still low. The next (optional) reset also sets the pixel
pointer to position (1,1) and additionally changes the dynamics to high (figure 7). Further
resets only set the pixel pointer to position (1,1) but do not change the dynamics which
remains high.
Note that switching on the sensor while reset is low can be interpreted as the first reset. In
this case, the next reset will change the dynamics to high. If the images must be read out
in low dynamics, the image from the first readout should not be used.
Figure 7: Changing the Dynamics to high after Readout of the Complete Image
3.7 Set the FingerTIP™ into Sleep Mode in EPP Mode
The FingerTIP™ offers a sleep mode to save power and increase the life time of the
sensor. In EPP mode the sensor can be switched to sleep mode by pulling down the reset
line for more than 2µs as shown in figure 8. Therefore it is recommended to switch the
sensor to sleep mode whenever there is no readout of an image. When the sensor is
switched back to readout mode, a new fingerprint can be acquired immediately.
Figure 8: Set the Sensor to Sleep Mode
TMin = 2 µsTMin = 1 µs
1st reset
set pixel pointer: (1,1)
/RESET
TMin = 2 µs
2nd reset
dynamics: low dynamics: high
set pixel pointer: (1,1)
Sensor in Readout Mode
/RESET
TMin = 2
µ
s
Sensor in Sleep Mode

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3.8 Fingerprint Image Readout
The following figure 9 shows the block diagram for a readout of the sensor in EPP mode.
Figure 9: Block Diagram for Image Readout in EPP Mode
RESET
Set pixel pointer: (1,1)
Set
dynamics
high?
YES
NO
STOP
set ´sleep mode´
store image
Read line
225 bytes
RESET
Set pixel pointer: (1,1)
Set dynamics to ´high´
NO
YES
LineEndMark
OK?
NO
YES
Read
288 lines?
NOYES Read
new image?
Store image
Stop readout procedure if:
- Timeout on the EPP interface
(TRea > 10µs)
- More than 3 times LineEndMark
Next Readout:
Dynamics will
be set to ´high´
SENSOR:
Power-On Reset
Wait 300µs

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Once the sensor has completed its power-on reset (see table 4), the readout of the
fingerprint image can be started. Before the first byte is read, the pixel pointer must be set
to position (1,1) (see figure 7). This is done by a reset impulse (low active) with TRst length
(see table 4). With a second reset the sensor can be set into high dynamics mode (see
section 3.6). Then the first byte of the image can be read out. 225 EPP read cycles are
needed for reading a complete line. The 225th byte of each line is the LineEndMark and
must be 00h. Interference such as ESD air discharge and alike can force double clocking
on the sensor under special conditions and the LineEndMark may not be 00h. Usually this
kind of interference is singular and temporary. Therefore it is recommended to start
reading a new image. Note that the dynamics is now high because the image was not read
out completely (see section 3.6). After 64800 (225 x 288) EPP read cycles the whole
image is read out.
If more than three readouts have failed because of LineEndMark error, the read out should
be stopped in order to analyze the error. It is also recommended to check for timeout
errors of the EPP port. If TEL > 10µs the readout should be stopped and the error should
be analyzed. For more information and error handling please see the Design-In Guideline
/2/.
Once the image readout is finished and the sensor is not needed for the moment, the
sensor should be set to sleep mode.
3.9 Pinout of the FingerTIP™ in EPP Mode
In figure 10, the pinout of the FingerTIP™ module is shown. Table 5 shows the pin
names, the pin direction and gives a short description of the pins.
Some of the pins are multi-functional pins, depending on the selected interface mode –
EPP or SPI. Chapter 5 gives a complete overview of the pins for EPP and SPI mode. The
pad characteristics are also shown in chapter 5.
Figure 10: Pinout of the FingerTIP™ Module
1
21
Module

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Pad no. Signal
Direction Signal Name Active Description
1 Prot. GND Protective Ground
2V
SS Signal Ground
3 Input EPP/SPI Select Interface Mode:
VCC*: EPP 1.9; Vss : SPI
4 Input /RESET Low Reset pixel pointer to position (1,1)
Change the Dynamics
5 Input /REQUEST Low Start a Readout of a Byte
6 Output READY High Indicates valid data on DA0 to DA7
(tristate in sleep mode)
7 Not used Do not connect
8 Not used Do not connect
9 Output DA0 Data line DA0 (tristate if not active)
10 Output DA1 Data line DA1 (tristate if not active)
11 Output DA2 Data line DA2 (tristate if not active)
12 Output DA3 Data line DA3 (tristate if not active)
13 Output DA4 Data line DA4 (tristate if not active)
14 Output DA5 Data line DA5 (tristate if not active)
15 Output DA6 Data line DA6 (tristate if not active)
16 Output DA7 Data line DA7 (tristate if not active)
17 Not used Do not connect
18 Not used Do not connect
19 VSS Signal Ground
20 VCC Supply voltage
21 Prot. GND Protective Ground
* using a 22K pull-up resistor
Table 5: Module Pin Description for EPP 1.9 Mode

FingerTIP™
Infineon Technologies 19/38 FTF 1100 MF1 V2.0 databook 3.3 (05.00)
3.10 Recommended Electrical Connection of the FingerTIP™ in EPP Mode
21 Protec. GND
20 Vcc
19 GND
18 NC
17 NC
16 D7
15 D6
14 D5
13 D4
12 D3
11 D2
10 D1
9 D0
8 NC
7 NC
6 READY
5 /REQUEST
4 /RESET
3 EPP/SPI
2 GND
1 Protec. GND
Vcc
INIT
BUSY
8
AutoLF
Molex-FFC/FPC
R2 (e.g. 33Ω)
R3 (e.g. 33Ω)
2/8 74XX245
Notice:
Place the resistors close to the outputs of the drivers
Place the drivers close to the outputs of the handshake/data lines
(if using a DB25 connector place the drivers into the connector)
shielded cable
DB25 / PC
1
13
25
14
GND
max 1.5 m
Connect pin 1 and 21 to protective ground
Protective GND R1 (e.g. 33Ω)
10µF
GND
R4 (≥22Ω)
10µF
R7 (e.g. 33Ω)
1/8 74XX245
R8 - R15 (e.g. 33Ω)
8/8 74XX245
R5 - R6 (e.g. 1KΩ)
2/8 74XX245
EN
GND
R16 (≥15KΩ)
(22KΩ) R16
Figure 11: Recommended circuit for interfacing the FingerTIP™ to an EPP Printer Port
The recommended circuit consists of 3 parts. The first consists of the drivers and resistors
between the DB-25 connector and the cable. The drivers are required to buffer the RESET
(AutoLF) and REQUEST (Init) handshake lines in the case of weak PC output drivers. This
is done to compensate for any potential PC signal issues. The serial resistors after the
drivers are required to reduce signal ringing. The value of these resistors is dependent on
the drivers used, but typical values are 33Ohm.
The second part is the cable. For a proper data transfer the cable must be shielded, and
the maximum length should be less than 1.5 meters. To guarantee clean signal quality it is
recommended to use several ground path wires to the PC chassis. On the sensor side of
the cable, the shield must be connected to pin 1 and 21 (protective ground) with a
dedicated line. Never connect the signal ground to protective ground on sensor side. This
connection configuration of the shield is required for optimal ESD protection.

FingerTIP™
Infineon Technologies 20/38 FTF 1100 MF1 V2.0 databook 3.3 (05.00)
The third part of the recommended circuit is consists of the drivers and resistors between
the cable and the 21-pin sensor-connector. The resistors R1 and R4 are required for both
supply current limitation and ESD protection. The drivers in the data and ready lines
decouple these lines from the EPP port. The combination of driver and resistor in the
RESET and REQUEST line limits a possible supply current of the sensor via these I/O
pins. The values of R5 and R6 will be dependent on the maximum output current of the
drivers, so it is recommended to choose such a combination of driver and resistor such
that the maximum current per handshake line is < 5mA.
For stabilising the sensor power supply, capacitors C1 and C2 are required.
4 The Serial Interface SPI
This chapter describes the serial interface of the FingerTIP™ and how to read out an
image, change the dynamics and set sleep mode. First the basic interface information, the
data transfer protocol and electrical and timing parameters of the sensor's SPI mode are
described. Then the readout procedure is illustrated by a block diagram. Finally, the pinout
of the sensor's SPI mode is shown.
For further information to design-in the sensor, please refer to the Design-In Guideline /2/.
4.1 Basic Information on the Serial Interface SPI
The FingerTIP™ Serial Peripheral Interface (SPI) can be operated with a clock rate of up
to 5 MHz depending on the supply voltage (see table 7). Every command sent by the
master is confirmed with a response from the sensor. The on-chip SPI interface allows bus
protocols for the SPI modes (0,0) and (1,1). With the rising edge of the clock the SPI
interface reads data from the SI pin while the SPI interface outputs data on the SO pin with
the falling edge of the clock. The data format of the commands, the corresponding
responses and the image data is 8-bit with LSB first. The SPI interface is implemented as
a 3-line bus consisting of input, output and clock signals plus a chip-select line. This allows
Multi-Master and Slave operation with bus-compliant systems.