AT77C104B-FingerChip - Atmel Corporation

1. Features

•Thermal Sensitive Layer Over a 0.35 µm CMOS Array

•Image Zone: 0.4 × 11.6 mm

•Image Array: 8 × 232 = 1856 Pixels

•Pixel Pitch: 50 × 50 µm = 500 dpi Resolution

•On-chip 8-bit Analog to Digital Converter

•Serial Peripheral Interface (SPI) - 2 Modes:

– Fast Mode at 16 Mbps Max for Imaging

– Slow Mode at 200 kbps Max for Navigation and Control

•Die Size: 1.5 × 15 mm

•Operating Voltage: 2.3 to 3.6V

•Operating Temperature Range: -40°C to 85°C

•Finger Sweeping Speed from 2 to 20 cm/Second

•Low Power: 4.5 mA (Image Acquisition), 1.5 mA (Navigation), <10 µA (Sleep Mode)

•Hard Protective Coating (>4 Million Sweeps)

•High Protection from Electrostatic Discharge

•Small Form Factor Packaging

•Comply with the European Directive for Restriction of Hazardous Substances (RoHS

Directive)

2. Description

This document describes the specifications of Atmel’s AT77C104B fingerprint sensor

dedicated to PDA, cellular and smartphone applications. Based on FingerChip® ther-

mal technology, the AT77C104B is a linear sensor that captures fingerprint images by

sweeping the finger over the sensing area. This product embeds true hardware-based

8-way navigation and click functions.

3. Applications

• Scrolling, Menu and Item Selection for PDAs, Cellular or Smartphone Applications

• Cellular and Smartphones-based Security (Device Protection, Network and ISP

Access, E-commerce)

• Personal Digital Agenda (PDA) Access

• User Authentication for Private and Confidential Data Access

• Portable Fingerprint

•Acquisition

Chip-on-board Package

Actual size of sensor

FingerChip®

Thermal

Fingerprint

Sweep Sensor,

Hardware

Based,

Navigation and

Click Function,

SPI Interface

AT77C104B

Sweep your finger

to make life easier

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AT77C104B

Note: The die attach is connected to pin 6 and must be grounded. The FPL pin must also be grounded.

Table 3-1. Pin Description for Chip-on-board Package: AT77C104B-CB08YV

Pin Number Name Type Description

1 Not connected

2 Not connected

3 Not connected

4 Not connected

5 GNDD G Digital ground supply

6 GNDA G Analog ground supply - connect to GNDD

7 VDDD P Digital power supply

8 VDDA P Analog power supply - connect to VDD

9 SCK I Serial Port Interface (SPI) clock

10 TESTA IO Reserved for the analog test, not connected

11 MOSI I Master-out slave-in data

12 TPP P Temperature stabilization power

13 MISO O Master-in slave-out data

14 SCANEN I Reserved for the scan test in factory, must be grounded

15 SSS I Slow SPI slave select (active low

16 IRQ O Interrupt line to host (active low). Digital test pin

17 FSS I Fast SPI slave select (active low)

18 RST I Reset and sleep mode control (active high)

19 FPL I Front plane, must be grounded

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Figure 3-1. Typical Application

The pull-up must be implemented for the master controller. The noise should be lower than 30

mV peak-to-peak on VDDA.

Figure 3-2. Pin Description

The TESTA pin is only used for testing and debugging. The SCANEN pin is not used in the final

application and must be connected to ground.

Warning: SSS and FSS must never be low at the same time. When both SSS and FSS equal

0, the chip switches to scan test mode. With the SPI protocol, this configuration is not

possible as only one slave at a time can be selected. However, this configuration

works when debugging the system.

TESTA

IRQ TPP

MISO VDDD

MOSI

SCK GNDD

SSS VDDA

FSS

SCANEN GNDA

FPL

RST

VDDA

10 kΩ10 kΩ

VDDD VDDD

10µF

GND

10µ

GND

VDDD

GNDD

GNDA

VDDD

VDDA

SCK

TESTA

MOSI

TPP

MISO

SCANEN

SSS

IRQ

FSS

RST

FPL

Bottom View Top View

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AT77C104B

4. Specifications

Table 4-1. Absolute Maximum Ratings

Parameter Symbol Comments Value

Power supply voltage VDDD, VDDA -0.5 to 4.6V Note: Stresses beyond those listed

under “Absolute Maximum

Ratings” may cause permanent

damage to the device. These are

stress ratings only and functional

operation of the device at these or

any other conditions beyond those

indicated in the operational

sections of this specification is not

implied. Exposure to absolute

maximum rating conditions for

extended periods may affect device

reliability.

Front plane FPL GND to VDD +0.5V

Digital input SSS, FSS,

SCK, MOSI GND to VDD +0.5V

Temperature stabilization

power TPP GND to VDD +0.5V

Storage temperature Tstg -50 to +95°C

Lead temperature

(soldering 10 seconds) Tleads Do not solder Forbidden

Table 4-2. Recommended Conditions of Use

Parameter Symbol Comments Min Typ Max Unit

Positive supply voltage VDD

2.5 ±5%

3.3 ±10% 2.3 2.5

3.3 3.6 V

Front plane FPL Must be grounded GND V

Digital input voltage CMOS levels V

Digital output voltage CMOS levels V

Digital load CL20 50 pF

Operating temperature range Tamb Domestic "D" grade -40 to +85 °C

Maximum current on TPP ITPP Use of TPP is optional 0 - 60 mA

Table 4-3. Resistance

Parameter Min Value Standard Method

ESD

On pins HBM (Human Body Model) CMOS I/O 2 kV MIL-STD-883 method 3015.7

On die surface (zap gun) air discharge ±16 kV NF EN 6100-4-2

Mechanical Abrasion

Number of cycles without lubricant

Multiply by a factor of 20 for correlation with a real finger 200 000 MIL E 12397B

Chemical Resistance

Cleaning agent, acid, grease, alcohol, diluted acetone 4 hours Internal method

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5. Power Consumption and DC Characteristics

The following characteristics are applicable to the operating temperature -40°C ≤ Ta ≤ +85°C.

Typical conditions are: power supply = 3.3V; Tamb = 25°C; FSCK = 12 MHz (1600 slices per sec-

ond); duty cycle = 50%

CLOAD 120 pF on digital outputs unless otherwise specified.

Table 4-4. Explanation of Test Levels

Level Description

I 100% production tested at +25°C

II 100% production tested at +25°C, and sample tested at specified temperatures (AC testing done on sample)

III Sample tested only

IV Parameter is guaranteed by design and/or characterization testing

V Parameter is a typical value only

VI 100% production tested at temperature extremes

D 100% probe tested on wafer at Tamb = +25°C

Table 4-5. Specifications

Parameter Symbol Test Level Min Typ Max Unit

Resolution IV 50 Micron

Size IV 8 × 232 Pixel

Yield: number of bad pixels I 5 Bad pixels

Equivalent resistance on TPP pin I 23 35 47 Ohm

Table 5-1. Power Requirements

Name Parameter Conditions Test Level Min Typ Max Unit-

VDD Positive supply voltage I 2.3 2.5/3.3 3.6 V

IDD Current on VDD in acquisition mode I 3 4.5 6 mA

IDDNAV Current on VDD in navigation mode I 1 1.5 2 mA

IDDCLI Current on VDD in click mode I 0.2 0.3 0.5 mA

IDDSLP Current on VDD in sleep mode I 10 µA

IDDSTB Current on VDD in stand-by mode I Refer to ”Power Management” on page 28

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Note: 1. A minimum noise margin of 0.05 VDD should be taken for Schmitt trigger input threshold switching levels compared to VIL and

VIH values.

Table 5-2. Digital Inputs

Logic Compatibility CMOS

Name Parameter Conditions Test Level Min Typ Max Unit

IIL

Low level input current without pull-

up device(1) VI = 0V I 1 µA

IIH

High level input current without

pull-down device(1) VI = VDD I1µA

IIOZ

Tri-state output leakage without

pull-up/down device(1) VI = 0V or VDD IV 1 µA

VIL Low level input voltage(1) I0.3 V

DD(1) V

VIH High level input voltage(1) I0.7 V

DD(1) V

VHYST Schmitt trigger hysteresis(1) VDD = 3.3V

Tem p = 2 5 °CIV 0.400 0.750 V

Table 5-3. Digital Outputs

Logic Compatibility CMOS

Name Parameter Conditions Test Level Min Typ Max Unit

VOL Low level output voltage

IOL = 3 mA

VDD = 3.3V ±10% I0.15 VDD

(1) V

IOL = 1.75 mA

VDD = 2.5V ±5%

VOH High level output voltage

IOH = -3 mA

VDD = 3.3V ±10% I0.85 V

DD V

IOH = -1.75 mA

VDD = 2.5V ±5%

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6. Switching Performances

The following characteristics are applicable to the operating temperature -40°C ≤ Ta ≤ +85°C.

Typical conditions are: nominal value; Tamb = 25°C; FSCK = 12 MHz; duty cycle = 50%; CLOAD 120

pF in digital output unless specified otherwise.

Note: 1. TSCK = 1/FCTRL (clock period)

Note: All power supplies = +3.3V

Note: All power supplies = +2.5V

Table 6-1. Timings

Parameter Symbol Test Level Min Typ Max Unit

Clock frequency acquisition

mode FACQ IV 8 16 MHz

Clock frequency navigation

mode and chip control FCTRL I- 0.2MHz

Duty cycle (clock SCK) DC IV 20 50 80 %

Reset setup time TRSTSU I½ T

SCK(1) ns

Slave select setup time TSSSU I½ T

SCK(1) ns

Slave select hold time TSSHD I½ T

SCK(1) ns

Table 6-2. 3.3V ±10% Power Supply

Parameter Symbol Test Level Min Typ Max Unit

Data in setup time TSU IV 3 ns

Data in hold time THIV 1 ns

Data out valid TVI30ns

Data out disable time from SS

high TDIS IV 3.8 ns

IRQ hold time TIRQ IV 3 µs

Table 6-3. 2.5V ±5% Power Supply

Parameter Symbol Test Level Min Typ Max Unit

Data in setup time TSU IV 3 ns

Data in hold time THIV 1 ns

Data out valid TVI30ns

Data out disable time from SS

high TDIS IV 3.8 ns

IRQ hold time TIRQ IV 3 µs

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7. Timing Diagrams: Slow and Fast SPI Interface

Figure 7-1. Read Timing Fast SPI Slave Mode

Figure 7-2. Read/Write Timing Slow SPI Slave Mode

Figure 7-3. Read Status Register to Release IRQ

Figure 7-4. Chip Initialization

Tsshd

Tdis

RST

SCK

MISO

Trstsu Tsssu DC

SCK

MOSI

MISO

Tsssu

Tsu Th

Tsshd

SCK

MOSI

IRQ

Tirq

11 0 0 0 X

RST

SCK

MISO

Min = 10 µs

Trstsu

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8. Functional Description

The AT77C104B is a fingerprint sensor based on FingerChip technology. It is controlled by an

SPI serial interface through which output data is also transferred (a slow SPI for the pointing

function and a fast one for acquisition). Six modes are implemented:

–Sleep mode: a very low consumption mode controlled by the reset pin RST. In this

mode, the internal clocks are disabled and the registers are initialized.

–Stand-by mode: also a low consumption mode that waits for an action from the

host. The slow serial port interface (SSPI) and control blocks are activated. In this

mode the oscillator can remain active.

–Click mode: waits for a finger on the sensor. The SSPI and control blocks are

activated. The local oscillator, the click array and the click block are all activated.

–Navigation mode: calculates the finger’s x and y movements across the sensor.

The SSPI and control blocks are still activated. The local oscillator, the navigation

array and the navigation block are also activated.

–Acquisition mode: slices are sent to the host for finger reconstruction and

identification. The SSPI and control blocks are still activated. The fast serial port

interface block (FSPI) and the acquisition array are activated, as well as the local

oscillator when watchdog is required.

–Test: this mode is reserved for factory testing.

In the final application, three main modes are used:

–Stand-by: low consumption mode

–Pointing: equivalent to click and navigation modes

–Acquisition: fingerprint image capture

Note: The term "host" describes the processor (controller, DSP...) linked to the sensor. It is the master. In

the description of n-bit registers (see ”Function Registers” on page 11), the term "b0" describes

the Least Significant Bit (LSB). The term “b(n-1)” describes the Most Significant Bit (MSB). Binary

data is written as 0b_ and hexadecimal data as 0x_.

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9. Sensor and Block Diagram

Figure 9-1. Functional Block Diagram

The circuit is divided into the following main sections:

• An array or frame of 8 x 232 pixels + 1 dummy column

• An analog to digital converter

• An on-chip oscillator

• Control and status registers

• Navigation and click units

• Slow and fast serial interfaces

TPP FPL VDDA GNDA VDDD GNDD RST

FSS

SCK

MISO

MOSI

SSS

IRQ

SCANEN

TESTA

Pixel Array

(232 x 8)

Array

CTRL

Click

CTRL

Click Pixels

(12)

Acquisition

Navigation

Algorithms

Oscillator (420 kHz)

Click

Algorithm

Watchdog

Heating

Test

Slow Serial

Interface

SPI

(200 kHz)

Control

Fast Serial

Interface

SPI

(8-16 MHz)

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10. Function Registers

Note: 1. Navigation requires 3 registers. The reading of the first register (0b1000) enables the reading

of all 3 registers.

10.1 Status Register

Access Type: Read Only

Function: State of AT77C104B

•CLICK: click detection

0: default

1: click detected

•MOV: movement detection

0: default

1: X or Y movement detected

• TRANSIT: not used, for testing only

• SLICE: not used, for testing only

Table 10-1. Registers

STATUS 0000 Read

MODECTRL 0001 Read/Write

ENCTRL 0010 Read/Write

HEATCTRL 0011 Read/Write

NAVCTRL 0100 Read/Write

CLICKCTRL 0101 Read/Write

MOVCTRL 0110 Read/Write

0111 Reserved

NAVIGATION(1) 1000 Read

NAVIGATION(1) 1001 Reserved

NAVIGATION(1) 1010 Reserved

PIXELCLICK 1011 Reserved

PIXELCLICK 1100 Reserved

PIXELCLICK 1101 Reserved

1110 Reserved

b7 b6 b5 b4 b3 b2 b1 b0

CLICK MOV TRANSIT SLICE READERR – – –

00000000

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•READERR: read error detection

0: default, no error

1: read error detected

Note: To clear the interrupts, the status register is initialized after each reading from the host.

10.2 Modectrl Register

Access Type:Read/Write

Function:Mode control

•MODE: select operating mode

0000: standby

0001: test (reserved for factory use)

0010: click

0100: navigation

1000: acquisition

Certain changes can be made. For example, MODE can be set to 0b0110 to activate click and

navigation.

•ANALOGRST: reset local oscillator

0: oscillator in active mode

1: oscillator in power-down mode

Notes: 1. Click or navigation modes cannot be used when the local oscillator is switched off. .

2. To return to standby mode and stop the oscillator (to save on power consumption), two Modec-

trl register accesses are

necessary: the first one to select standby mode and the second to switch off the oscillator.

3. The read-only registers cannot be read when the oscillator is turned off.

4. To shift between navigation and acquisition modes, you must be in standby mode (Modectrl =

0b00001).

If modes such as “acquisition and click” or “acquisition and navigation” are programmed

together, they will be ignored by the system.

With x = 0 or 1.

b6 b5 b4 b3 b2 b1 b0

MODE (MSB) MODE MODE MODE (LSB) ANALOGRST – –

0000100

Programmed Mode Register Value

11xx 01xx

1x1x 0x1x

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10.3 Enctrl Register

Access Type:Read/Write

Function: Interrupts control

•CLICKEN: click interrupts enable

0: default

1: click IRQ enabled

IRQ is generated when a click is detected.

•MOVEN: movement interrupts enable

0: default

1: movement IRQ enabled

IRQ is generated when an X or Y movement is detected.

•TRANSITEN: not used, for testing only

•SLICEN: not used, for testing only

•READERREN: read error interrupts enable

0: default

1: read error IRQ enabled

IRQ is generated when a read error is detected.

Note: The interrupt is cleared after the status register is read.

10.4 Heatctrl Register

Access Type:Read/Write

Function:Heating control

•HEAT: sensor heating

0: default, no heating

1: heating

The default value is recommended to optimize power consumption.

b6 b5 b4 b3 b2 b1 b0

CLICKEN MOVEN TRANSITEN SLICEN READERREN – –

0000000

b6 b5 b4 b3 b2 b1 b0

HEAT WDOGEN HEATV (MSB) HEATV(LSB) – – –

0000000

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•WDOGEN: watchdog enable

0: default

1: watchdog enabled

Watchdog automatically stops heating of the sensor after a time-out.

•HEATV (2 bits): heating power value

00: 50 mW

01: 100 mW

10: reserved

11: reserved

VDD is between 2.6 and 3.6V.

Notes: 1. Heating can only be used in the acquisition mode (it is not allowed in navigation or click

modes).

2. The oscillator has to be activated when the watchdog is required and must not be stopped

while the watchdog remains active.

10.5 Navctrl Register

Access Type:Read/Write

Function:Navigation control

•NAVFREQ: navigation frequency

00: 5.8 kHz

01: 2.9 kHz (default value)

10: 1.9 kHz

11: 1.5 kHz

A faster frequency enables faster finger movement detection. A lower frequency enhances sen-

sitivity. Refer to notes 1 and 2 on page 15.

•NAVV: navigation pixels threshold

00: lower threshold

01:

10:

11: higher threshold

Sets the minimum analog value detected as a high level (‘1’). Refer to note 1 on page 15.

•CLICKV: click pixels threshold

00: lower threshold

01:

10: higher threshold

11: reserved

b6 b5 b4 b3 b2 b1 b0

NAVFREQ

(MSB) NAVFREQ (LSB) NAVV ( MSB) NAVV (LSB) CLICKV (MSB) CLICKV (LSB) reserved

1000000

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Sets the minimum analog value detected as a high level (‘1’) and the maximum analog value

detected as a low level (‘0’). See note 3.

Notes: 1. Navfreq and Navv registers should not be changed once the navigation mode is selected. Fin-

ger sensitivity refers to the minimum level of information required from a finger. The sensitivity

is linked to the integration time; a longer integration time enables better sensitivity but does not

tolerate fast movement.

2. The navigation frequency is the frequency needed for the reading of one new navigation

frame.

3. The Clickv register should not be changed once the click mode is selected.

10.6 Clickctrl Register

Access Type:Read/Write

Function:Click control

•CLICKFREQ: click pixels reading frequency

00: 180 Hz

01: 90 Hz (default value)

10: 60 Hz

11: 45 Hz

Faster frequency enables faster finger click detection. Lower frequency enables higher

sensitivity.

•CLICKDET: threshold for selecting the black/white color of a slice

00: more than 7 black/white pixels and less than 5 white/black pixels

01: more than 8 black/white pixels and less than 4 white/black pixels

10: more than 9 black/white pixels and less than 3 white/black pixels

11: more than 10 black/white pixels and less than 2 white/black pixels

•CLICKCPT: click detection counter (maximum number of slices read between two

transitions)

000: 5

001: 7

010: 10

011: 12

100: 16

101: 20

110: 25

111: 31

b6 b5 b4 b3 b2 b1 b0

CLICKFREQ

(MSB)

CLICKFREQ

(LSB)

CLICKDET

(MSB)

CLICKDET

(LSB)

CLICKCPT

(MSB) CLICKCPT CLICKCPT

(LSB)

0101101

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Two transitions are interpreted as a click if the number of slices between them is less than

CLICKCPT. This is used to differentiate a touch-down/touch-up from a real click. A click is equiv-

alent to two close touch-down/touch-up transitions.

This register adjusts the “time out” for considering the two transitions as a click.

Note: Clickfreq and Clickcpt registers should not be changed once the click mode is selected.

10.7 Movectrl Register

Access Type: Read/Write

Function: In stream mode, during navigation calculation, the AT77C104B must

interrupt the host when a maximum absolute X or Y movement is detected (second and third

navigation registers). The MOVECTRL register enables you to control this value. This value can

be set as the minimum finger movement value at which the pointing device makes a

displacement.

•MOVCTRL: generates an interrupt when the second or third navigation register (X or Y

absolute movement) is greater than the value programmed in the Movectrl register

0b0000000

0b0000001

0b0000010

...

0b1111111

For example, when MOVCTRL = 0b0001001, an interruption to the host is generated when the

absolute X movement register (second navigation register) or absolute Y movement register

(third navigation register) is greater than 0b00010010.

Note: The Movctrl register should not be changed once the navigation mode is selected.

10.8 Navigation Register

Access Type: Read Only (these three registers cannot be read individually . The reading com-

mand of the first navigation register [address 0b1000] returns the value of the three registers).

Function: The format of the navigation registers is similar to the PS/2 protocol. Three registers

are used to codemovements and clicks. The navigation registers are initialized after each read-

ing. The registers only represent actions (movement, click, transition...) that have occurred since

the last data packet sent to thehost.

b6 b5 b4 b3 b2 b1 b0

(MSB) – – – – – (LSB)

0000000

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10.8.1 General Register

•YOVR: Y overflow

0: default

1: Y movement overflow

High (‘1’) when the Y movement counter is overflowed.

•XOVR: X overflow

0: default

1: X movement overflow

High (‘1’) when the X movement counter is overflowed.

•YSIGN: Y sign bit

0: default, positive Y movement

1: negative Y movement

High (‘1’) when the Y movement is negative. Low when the Y movement is positive.

•XSIGN: X sign bit

0: default, positive X movement

1: negative X movement

High (‘1’) when the X movement is negative. Low when the X movement is positive.

•TRANS: not used, for test purposes only.

•CLICK: Click

0: default

1: click detected

This function is not in the PS/2 protocol.

•FINGER: not used, for test purposes only.

Note: In the PS/2 protocol, bits b2 and b1 are used to code the middle and right buttons respectively,

and b3 is set to high.

b7 b6 b5 b4 b3 b2 b1 b0

YOVR XOVR YSIGN XSIGN 1 TRANS CLICK FINGER

00001000

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10.8.2 Absolute X Movement Register (0 to 255 Pixels)

10.8.3 Absolute Y Movement Register (0 to 255 Pixels)

Note: When a click is detected, the information is placed in the b7 bit of the status register and in the b1

bit of the general navigation register. The reading of the status register initializes the b7 bit but

does not initialize the b1 bit of the general navigation register. The host must carefully correlate

the two bits.

11. SPI Interface General Description

Two communication busses are implemented in the device:

• The control interface, a slow bus that controls and reads the internal registers (status,

navigation, control...).

• The pixels’ acquisition interface, a fast bus that enables full pixel acquisition by the host.

A synchronous Serial Port Interface (SPI) has been adopted for the two communication busses.

The SPI protocol is a slave/master full duplex synchronous serial communication. This protocol

uses three communication signals:

• SCK (Serial Clock): the communication clock

• MOSI (Master Out Slave In): the data line from the master to the slave

• MISO (Master In Slave Out): the data line from the slave to the master

The slaves are selected by an input pin SS/ (Slave Select). A master can communicate with sev-

eral slaves.

The word length of the transferred data is fixed to 8 bits. The Most Significant Bit (MSB) is sent

first. For each 8-bit transfer, 8 bits are sent from the master to the slave and 8 bits transferred

from the slave to the master. Transfers are still synchronized with the communication clock

(SCK). Only the host can initialize transfers. To send data, the slave must wait for an access

from the master. When there is no transfer, a clock is not generated.

b7 b6 b5 b4 b3 b2 b1 b0

XMOV (MSB)––––––XMOV (LSB)

00000000

b7 b6 b5 b4 b3 b2 b1 b0

YMOV (MSB)––––––YMOV (LSB)

00000000

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Figure 11-1. One Master with Several Slaves

When a master is connected with several slaves, the signals SCK, MISO and MOSI are inter-

connected. Each slave SS/ is driven separately. Only one slave can be selected, the others

have their MISO tri-stated and ignore MOSI data.

The SS/ signal falls a half-period before the first clock edge, and rises a half-period after the last

clock edge.

11.1 Clock Phase and Polarity

During phase zero of the operation, the output data changes on the clock’s falling edge and the

input data is shifted in on the clock’s rising edge. In phase one of the operation, the output data

changes on the clock’s rising edge and is shifted in on the clock’s falling edge.

Polarity configures the clock’s idle level, which is high ('1') during polarity one of the operation

and low ('0') during polarity zero of the operation.

11.2 AT77C104B and the SPI

The AT77C104B is always the slave and the host always the master. The host drives the SCK

clock. Both the AT77C104B and the host transmit data with the MISO signal. The word length of

the transferred data is fixed to 8 bits. The Most Significant Bit (MSB) is sent first.

The AT77C104B supports only one phase and polarity configuration:

• The clock’s idle level set to high (polarity 1)

• The output data changed on the clock’s falling edge, and input data shifted in on the clock’s

rising edge (phase 0).

Figure 11-2. SPI Waveform (Phase = 0, Polarity = 1)

Note: During initialization of the SCK wire (power-on or reset), SS/ has to be inactive (‘1’).

Slave #1 Slave #3

Master

SS/3

SS/2

SS/1

SCK

MISO

MOSI

Slave #2

SCK

MOSI/MISO

SS/

Emission Reception

MSB LSB

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11.2.1 Recommendations

The SSS or FSS falling edge should be half a clock cycle before the first SCK falling edge and

the SSS or FSS rising edge should be half a clock cycle after the last SCK

rising edge.

11.3 SPI Behavior with Hazardous Access

The control register block uses an internal finite state machine that can only be initialized by the

RST pin (asynchronous reset). When SPI access does not use 8 clock pulses, the internal finite

state machine is desynchronized. The only way to resynchronize it is by resetting the sensor

with the RST pin. No requester modification is recorded when a write access is made on a read-

only register. Reliable initialization of read-only registers is not guaranteed when the slow SPI’s

maximum clock frequency is not respected.

12. Control Interface (Slow SPI)

This interface controls the sensor’s internal registers. The protocol enables reading and writing

of these registers.

The master (host) initiates transfers to the slave (sensor). The sensor can only use its interrupt

pin to communicate with the host. When the host is interrupted, it must read the status register

before continuing operation.

The word length of the transferred data is fixed to 8 bits. The Most Significant Bit (MSB) is sent

first.

12.1 Communication Protocol

Accesses to the host are structured in packets of words. The first word is the command and the

other words are the data.

The b7 bit is used to differentiate the command and data. When the word is a command, b7 is

high ('1') and when the word is a piece of data, b7 is low ('0').

The following protocol is used:

12.1.0.1 Command Format

The host indicates to the sensor if it wants to read or write into a register and indicates the regis-

ter’s address.

12.1.0.2 Data Format (Writing into Register)

If writing into a register, the host transmits the data.

b7 b6 b5 b4 b3 b2 b1 b0

1Read

(1)/Write (0) Address (b3) Address (b2) Address (b1) Address (b0) x x

b7 b6 b5 b4 b3 b2 b1 b0

0 Data (b6) Data (b5) Data (b4) Data (b3) Data (b2) Data (b1) Data (b0)

5347C–BIOM–02/06

AT77C104B

12.1.0.3 Data Format (Reading of Register)

If reading a register, the host transmits one or several packets of data and data is shifted in from

the sensor. The host transmits dummy words with the data format (b7 is low ['0’]). If reading the

navigation or pixelclick registers, the host transmits three packets of data to read the three

registers.

Note: The host cannot communicate with the sensor without receiving data from it. Useless data is ignored by the host.

12.2 Communication Speed

To reduce consumption, the control interface’s communication speed is set to the lowest possi-

ble speed and depends on the host’s configuration.

To communicate with “fast” controllers, the sensor’s communication speed can be set to 200

kbits/s.

12.2.1 Example for the MODECTRL Register

Figure 10 represents a typical writing sequence into an internal register (MODECTRL register in

this example).

See Appendix B for flowchart.

Figure 12-1. Writing into an Internal Register

Note: The break on SCK on the SPI chronogram has been added for better comprehension only. In a real application, SCK can be

continuous.

b7 b6 b5 b4 b3 b2 b1 b0

0xxxxxxx

SSS

SCK

MOSI

MISO

xxx xxxx x xxx xxxx x

00110000

10000 xx1

Writing into MODECTRL Register Requested New Data to be Written into MODECTRL Register

(Navigation and Click Mode)

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AT77C104B

Figure 12-2 represents a typical reading sequence of a register different from the navigation reg-

ister. In this example, the status register is used.

Figure 12-2. Reading Sequence of a Register (Except for Navigation Registers)

12.3 Example of Navigation Registers

Figure 12 represents a typical reading sequence of the three navigation registers.

Refer to ”Appendix C” on page 33 for flowchart

Figure 12-3. Reading of the Navigation Registers

13. Image Capture (Fast SPI)

This serial interface enables full-speed acquisition of the sensor’s pixels by the host.

This interface only supports the serial clock (SCK) and one data line: MISO (Master In/ Slave

Out).

SCK

MOSI

MISO

xxx xxxx x 100 0000 0

0xx xxxx

11000 x x0

Reading of STATUS Register Requested Emission of the STATUS Register

(Click Detected)

SCK

MISO

MOSI

Reading of Navigation

X X

XX X X

X0 1 0

0 10

00 0

1 0 0 00 0 0 1 0 0 0 0

0 0 0 X X

X X X X

X XXX

0XX X XX X X

Emission of the First

Navigation Register

(No Overflow, Y Negative Movement

Click Detected, Black Slice)

Emission of the Second

Navigation Register

(X Absolute Movement

= 24 Pixels)

Emission of the Third

Navigation Register

(Y Absolute Movement

= 144 Pixels)

5347C–BIOM–02/06

AT77C104B

13.1 Communication Protocol

When the sensor is in acquisition mode, the host can receive pixels through the fast SPI (FSS/ =

0). The host must transmit the communication clock (SCK) to receive the pixels. This clock must

have a regular frequency to obtain constant fingerprint slices (See “Registration Integration

Time” on page 25.).

With the sensor configured to acquisition mode, the controller can proceed to fast accesses.

Figure 13-1. Example of an 8-bit Access

During an 8-bit access, the sensor transmits two pixels (each pixel is coded on 4 bits).

Figure 13-2. Fast SPI Communication

13.2 Communication Speed

The acquisition speed of the pixels is linked to the clock’s communication speed. The faster the

communication clock, the faster the authorized maximum finger sweeping speed. The sensor

supports fast communications up to 16 Mbps.

13.3 Reading of Frame

A frame consists of 232 true columns and 1 dummy column of 8 pixels of 4 bits each. A frame

starts with a dummy column.

FSS/ = 0

Sending of Dummy Data

0b0000000

Reception of 2 Pixels

End of

Communication

Sending of 2 Pixels (8 Bits)

FSS/ = 1

Yes

Controller

Sensor

Bit2

Bit3

MSB

Bit1 Bit0 Bit3 Bit2 Bit1 Bit0 Bit2 Bit1 Bit0 Bit3 Bit2 Bit1 Bit0

Bit3

MSB

SCK (Pixel Clock)

MISO

Transmission Clock

Edge (Sensor)

Reception Clock

Edge (Host)

Pixel 2i Pixel 2i - 1 Pixel 2i + 2 Pixel 2i + 1

5347C–BIOM–02/06

AT77C104B

Figure 13-3. Example of a Frame

The first dummy column, at the beginning of the pixel array, is added to the sensor to act as a

specific easy-to-detect pattern, and represents the start of the frame tag.

The pixel array is always read in the following order: the first byte, following the 4 bytes of the

dummy column, which contains the value of the pixels physically located on the upper left corner

of the array, when looking at the die with bond pads to the right. Then another 4 bytes are read

that contain the value of the pixels located in the same column from top to bottom. The next col-

umn on the right is output, and so on, until the last line on the right, close to the bond pads, is

output.

Even values are first sent during the data serialization for SPI transfer. Therefore, the synchroni-

zation sequence on the chip’s MISO output is F0F00200.

Figure 13-4. Reading of Frame

Notes: 1. For the first array or frame reading, 40 dummy clock cycles must be sent before the first data arrives. This is necessary for

the initialization of the chip pipeline. Consequently, the first synchronization sequences appear after 40 clock cycles. For the

following array readings, data arrives at each clock cycle. One should implement a synchronization routine in the protocol to

look for the F0F00200 pattern.

2. The Most Significant Bit (MSB) is sent first.

13.4 Reading of Entire Image

The FingerChip delivers fingerprint slices or frames with a height of 0.4 mm and a width of 11.6

mm (this equals 8 × 232 pixels). Pixels are sampled/read sequentially and are synchronous with

SCK. Raw slices are captured by the acquisition system and overlapped with the corresponding

X or Y finger displacement computed by Atmel reconstruction software. This reconstruction soft-

ware supports a sweeping speed from 2 to 20 cm/s.

Pixel Frame

p10

p11

P12

P13

P14

P15

p16

Synchro = F0F00200

Dummy

Column 232 x 8 Pixels Column

SCK

MISO

Dummy Column

F 0 F 0 20 0 P2 P1 P4 P6 P3 P5 P8 P7

First Pixel

Column

0 P10 P9

Second Pixel

Column

5347C–BIOM–02/06

AT77C104B

The table below shows finger speeds according to the different clock frequencies. The recon-

struction results are obtained after acquisition of all slices.

13.5 Registration Integration Time

The pixel’s integration time (the time needed for one frame reading) must be as regular as possi-

ble to obtain consistent fingerprint slices. This time is directly dependant on the SCK, SPI clock

and frequency. Therefore, the SPI cycle of 4 × 8 × 233 clock pulses should be as regular as

possible.

Figure 13-5. Regular Integration Time

Note: The 500 µs duration corresponds to the host’s computation time (slice reconstruction, finger detection…) and in the illustration is

given as an example only. Once the host detects a finger, this value remains constant, thus guaranteeing a regular integration

time.

14. Navigation (Slow SPI)

The sensor’s navigation function includes the processing elements necessary for providing the

displacement of the finger touching the sensor in an up or down and right or left direction. It is

aimed at a screen menu navigation or simple pointing application. In addition, a click processing

function is embedded to detect a quick touch of the finger on the sensor. It is aimed at screen

text, box or object selection. A double-click function could also be implemented in the software.

This interface has been designed to resemble the PS/2 mouse protocol.

An interrupt signal IRQ indicates to the host that an action has been detected. The host must

read the status register to obtain details on the action. The IRQ signal enables implementation of

an efficient power consumption protocol.

Table 13-1. Finger Speeds Versus Clock Frequencies

Fsck

(MHz)

Data Rate

(Mbit/s)

Slice Rate

(Slices/s)

Absolute

Maximum Finger

Speed (cm/s) Comments

1 1 134 3 Too slow

2 2 268 6 Too slow

4 4 536 12 Minimum

6 6 804 18 Normal speed

8 8 1072 24 Good speed

12 12 1608 36 Very good speed

16 16 2146 48 Very good speed

Clock SCK

Regular Integration Time

Frame n

4 x 8 x 233 =

7456 Pulses

Frame n+1

7456 Pulses

Frame n+2

7456 Pulses

Frame n+3

7456 pulses

500 us max

233 = 232 + 1 Dummy Column

5347C–BIOM–02/06

AT77C104B

Note:

• Click and navigation modes can be used together.

• Two configurations are implemented for the click and navigation modes:

– Stream mode, where the sensor sends an interrupt to the host when a movement or

a change in the button’s state is detected.

– Remote mode, where the sensor does not interrupt the host but waits for its registers

to be read.

In these two modes, the registers are initialized after each reading from the host.

See “Appendix D” on page 34. for an example of an interrupt generated by a movement

detection.

14.1 Navigation

See “Navigation Register” on page 16.

The typical navigation slice frequency has been fixed to 2.9 kHz. A programmable divider is

implemented in the control registers (NAVFREQ) to reduce this frequency. Finger displacement

is provided as a number of pixels in X and Y directions. Negative movements are possible. The

decremented between two accesses.

14.2 Click

See “Clickctrl Register” on page 15.

The sensor generates a click detection. The host must read the b7 bit of the status register or

the b1 bit of the general navigation register.

The click function is composed of an array of a few pixels and a processing unit. The typical click

slice frequency is 90 Hz. A programmable divider is implemented to modify this frequency in the

control registers (CLICKFREQ).

14.3 Double-click

This function is performed by the controller, allowing better flexibility. It detects a succession of

two clicks.

Navctrl

(Bits b6 to b5)

Typical Navigation

Slice Frequency

(kHz)

Typical

Integration Time

(µs)

Typical Maximum

Finger Speed

(cm/s)

00 5.8 172 30

01 2.9 345 15

10 1.9 526 9.5

11 1.5 666 7.5

5347C–BIOM–02/06

AT77C104B

15. Temperature Stabilization Function and Watchdog

The sensor has an embedded temperature stabilization unit that identifies a difference in tem-

perature between the finger and the sensor. When this difference is increased, the images are

more contrasted. This function is optional and its use depends on the quality of the image pro-

cessing software, therefore its management should be decided together with the image

processing software.

In order to limit excessive current consumption by the use of the temperature stabilization func-

tion, a watchdog has been implanted in the sensor. The local oscillator stops the heating of the

module after a defined time. The oscillator should not be stopped as long as watchdog is active,

otherwise the clock stops automatically.

When heating of the sensor is requested '1' is written in bit 6 of the HEATCTRL

sor is heated during ‘n’ seconds.

Due to the oscillator frequency dispersion, the value of n is:

2 seconds (minimum) < n = 4 seconds (typical) < 7 seconds (maximum).

The accuracy of n is not important since the heat register can be enabled successively.

The level of power consumption is programmable. Two pre-programmed values are set to 50 or

100 mW.

The dissipated die power is quasi constant over a significant supply voltage range as shown

below (mode 50 mW selected):

Note: This function is useless for navigation and click modes.

Power = f ( Vdd )

4,80E-02

4,90E-02

5,00E-02

5,10E-02

5,20E-02

5,30E-02

5,40E-02

2 2,2 2,4 2,6 2,8 3 3,2 3,4 3,6 3,8

VDD

Power ( W )

Power = f ( Vdd)

5347C–BIOM–02/06

AT77C104B

16. Power Management

16.1 Sleep Mode (<10 µA)

Reset high

16.2 Standby Mode (<10 µA Providing SPI Bus not Accessed)

Power consumption can be reduced in several ways:

• By switching off the FingerChip sensor

• By programming a standby mode by writing 00001xx in the MODCTRL register (STANDBY

mode set and oscillator stopped.) Bit b6 (HEAT) of the HEATCTRL register must be turned to

‘0’ when programming standby mode

16.3 Acquisition Mode Current Consumption

16.3.1 Static Current Consumption

When the SPI bus is not used, only the analog part of the circuit consumes power at around 4

mA.

16.3.2 Dynamic Current Consumption

When the clock is running, the digital sections also consume current. With a 30 pF load at 16

MHz, the power consumption is approximately 4.5 mA on the VDD pins.

16.4 Navigation and Click Modes Current Consumption

16.4.1 Static Current Consumption

The SPI bus’ consumption is very low in click and navigation modes, the majority of the con-

sumption being generated by the analog part of the circuit. Therefore, the static and dynamic

consumption is almost the same.

16.4.2 Dynamic Current Consumption

With a 30 pF load at maximum clock frequency, the current consumption in click mode is almost

300 µA on pins VDD. With a 30 pF load at maximum clock frequency, the current consumption in

navigation mode is approximately 1.5 mA.

Note: We advise use of the interrupt capabilities (IRQ signal or Interrupts register) so as to limit the

host’s overall current consumption. The host can, from time to time, check the IRQ or Interrupt

The click mode is only 300 µA, and once a click is detected the host can turn on the navigation

mode as well.

5347C–BIOM–02/06

AT77C104B

17. Packaging Mechanical Data

Figure 17-1. AT77C104B-CB08YV Top View

All dimensions in mm.

Figure 17-2. AT77C104B-CB08YV Bottom View

All dimensions in mm.

17.1 Package Information

17.1.1 Electrical Disturbances

Three areas of the FingerChip device must never be in contact with the casing, or any other

component, so as to avoid electrical disturbances. These areas are shown in Figure 21:

Figure 17-3. Sensitive Areas

Figure 17-4. Epoxy Overflow

Maximum epoxy overflow width: 0.35 mm on the die edge.

Maximum epoxy overflow thickness: 0.33 mm.

23 ±0.3

4.6 max

1.1 min

0.74 ±0.06

1.2 max

0.56 ±0.1

4.8 ±0.4

1.75 ±0.5

4.8 max

5 ±0.3

11.98

0.2

+0.07

1.50 - 0.01

0.5 ±0.08

2.25 ±0.3 0.5 ±0.08

1.5 ±0.3

2 ±0.08

19 1

11.5 mm

6 mm

5347C–BIOM–02/06

AT77C104B

Note: Refer to Figure 17-1 on page 29.

18. Ordering Information

18.1 Package Device

0.35

0.33

Fingerchip Epoxy Glue Overflow

AA Section

AT77C

Atmel prefix

FingerChip family

Device type

Temperature range

V: -40˚ to +85˚C

Quality Level: Standard

Package

CBXX: Chip On Board (COB)

CBXX

104B V_

RoHS compliant

5347C–BIOM–02/06

AT77C104B

19. Appendix A

19.1 Controller Initialization

Controller

Initialized ?

Host Controller

Initialization

SPI Initialization

(Phase = 0, Polarity = 1)

SPI

Initialized ?

Yes

RST = 1

Sensor Initialization

Pulse

> 10 us ?

Yes

RST = 0

5347C–BIOM–02/06

AT77C104B

20. Appendix B

20.1 Example for the MODECTRL Register

Interrupts Masked

SSS/ = 0

Yes

MODECTRL Writing Requested

Sending of 0b10000100

Transfer

ended ?

Yes

MODECTRL Reading

Requested

Reception of the Command

Reading of MODECTRL

Modification of MODECTRL to

Change Mode Bits

Sending of the New

MODECTRL

Transfer

ended ?

Yes

Reception of MODECTRL

SSS/ = 1

Interrupts enabled

Sensor

Controller

Reception of the Command

Writing of MODECTRL

Sending of MODECTRL

Sending 0b11000100

Transfer

Ended ?

Modification of MODECTRL to

Change Mode Bits

Transfer

Ended ?

5347C–BIOM–02/06

AT77C104B

21. Appendix C

21.1 Example of Navigation Registers

Interrupts Masked

SSS/ = 0

Yes

Transfer

Ended ?

NAVIGATION Reading

Requested

Reception of the Command

Reading of NAVIGATION

Sending of Dummy Data

0b00000000

Reception of NAVIG2

Yes

Sending of NAVIG3

Sending of Dummy Data

0b00000000

Reception of NAVIG3

Sensor

Controller

Sending of NAVIG2

Sending of NAVIG1

Sending 0b11000000

Transfer

Ended ?

Sending of Dummy Data

0b00000000

Reception of NAVIG1

Transfer

Ended ?

Transfer

Ended ?

SSS/ = 1

Interrupts Enabled

Yes

5347C–BIOM–02/06

AT77C104B

22. Appendix D

23. Example of an Interrupt Generated by a Movement Detection

Interrupts Masked

SSS/ = 0

Yes

NAVIGATION Reading

Requested

Sending of 0b11100000

Transfer

Ended ?

Yes

STATUS Reading Requested

Sending of 0b11000000

Reception of the Command

Interrupts Control

Detection of Movement

Sending of Dummy Data

0b00000000

Reception of the 3 Navigations

3 Registers

Values Sent ?

Yes

Sending of the 3

Navigation Registers

SSS/ = 1

Interrupts enabled

Sensor

Controller

Reception of the Command

Reading of NAVIGATION

Sending of STATUS

Interrupts Cleared

Transfer

Ended ?

Transfer

Ended ?

Main Program

Interrup ? No

Sending of Dummy Data

0b00000000

Reception of STATUS

Interrupt Generated

IRQ/ = 0

Printed on recycled paper.

5347C–BIOM–02/06

marks or trademarks , FingerChip® is the registered trademark of Atmel Corporation or its subsidiaries. Other terms and product names may be

trademarks of others.

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intellectual property right is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN ATMEL’S TERMS AND CONDI-

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