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FT7681-DataSheet-20151104

FT7681

True Multi-Touch

Capacitive Touch

Panel Controller

INTRODUCTION

The FT7681 is single-chip capacitive touch panel controllers with built-in enhanced Micro-controller unit (MCU).It provides the benefits of full screen common mode scan technology,fast response time and high level of accuracy.It can drive capacitive type touch panel with up to 35 driving and 28 sensing lines.

FEATURES

● AEC-Q100 qualification: Grade 3 (2016/Q1) ● Mutual Capacitive Sensing Techniques ● Full Screen Common Mode Scan Techniques ● True Multi-touch up to 10 Points of absolute X and Y Coordinates ● High immunity to RF and power Interferences ● 7681 Supports up to 35TX + 28 RX

● Full Programmable Scan Sequences to Support Various TX/RX Configurations ● High Report Rate: Over 100Hz

● Touch Resolution of 325 Dots per Inch (dpi) or above ● Auto-calibration ● Support Interfaces:I2C

● Built-in 64KB Flash

● 2.8 to 3.6V Operating Voltage

● IOVCC (Ext. or Int.) supports from 1.8V to 3.6V ● Single Channel(TX/RX)resistance: Up to 100K ? ● Single Channel (transmit/receive) Capacitance: 20pF ● Optimal Sensing Mutual Capacitor: 0.5pF~4pF ● 12-Bit ADC Accuracy

● 3 Operating Modes Active Monitor Hibernation

● Operating Temperature Range: -40°C to +85°C ● Package:

TQFP80 10x10x1mm, 0.4mm/pitch

INTRODUCTION ........................................................................................................................................................... I FEATURES .................................................................................................................................................................... I 1 OVERVIEW ........................................................................................................................................................... 3 1.1 T YPICAL A PPLICATIONS ................................................................................................................................... 3 2

FUNCTIONAL DESCRIPTION (3)

2.1 A RCHITECTURAL O VERVIEW ........................................................................................................................... 3 2.2 MCU ................................................................................................................................................................ 4 2.3 O PERATION M ODES ........................................................................................................................................ 4 2.4 H OST I NTERFACE ............................................................................................................................................ 5 2.5 S ERIAL I NTERFACE .......................................................................................................................................... 5 3 ELECTRICAL SPECIFICATIONS (6)

3.1 A BSOLUTE M AXIMUM R ATINGS ....................................................................................................................... 6 3.2 DC C HARACTERISTICS .................................................................................................................................... 7 3.3 AC C HARACTERISTICS .................................................................................................................................... 8 3.4 I/O P ORTS C IRCUITS ....................................................................................................................................... 9 3.5

POWER ON/R ESET S EQUENCE (9)

1 OVERVIEW

1.1

Typical Applications

FT7681 accommodates a wide range of applications with a set of buttons up to a 2D touch sensing device; their typical applications are listed below. ● Automotive

● Factory Equipment

● Navigation systems, GPS ● Game consoles

● POS (Point of Sales) devices

● Portable MP3 and MP4 media players

● Digital cameras

FT7681 support Touch Panel, the spec is listed in the following table,

Part Number Package TX

Total Channels

Recommended for

Tablet TP Size FT7681LPZ

TQFP 80 10x10x1mm

Pitch =0.4mm

35 28

≦12”,

Sensor Pitch:6.8mm

2 FUNCTIONAL DESCRIPTION

2.1 Architectural Overview

Figure2-1 shows the overall architecture for the FT7681.

Figure 2-1 System Architecture Diagram

The FT7681 is comprised of five main functional parts listed below,

● Touch Panel Interface Circuits

The main function for the AFE and AFE controller is to interface with the touch panel. It scans the panel by sending AC signals to the panel and processes the received signals from the panel. It includes both Transmit (TX) and Receive (RX) functions. Key parameters to configure this circuit can be sent via serial interfaces. ● Enhanced MCU with DSP accelerator

For the Enhanced MCU, larger program and data memories are supported. Furthermore, a Flash memory is implemented to store programs and some key parameters.

Complex signal processing algorithms are implemented by MCU and DSP accelerator to detect the touches reliably and efficiently. Communication protocol software is also implemented in this MCU to exchange data and control information with the host processor.

● External Interface

I2C: an interface for data exchange with host

INT: an interrupt signal to inform the host processor that touch data is ready for read

RSTN: an external low signal reset the chip. The port is also use to wake up the FT7681 from the Hibernate mode.

●A watch dog timer is implemented to ensure the robustness of the chip.

●A voltage regulator to generate 1.8V for digital circuits from the input VDD3 supply

●Power On Reset (POR) is active until VDDD is higher than some level and hold decades of μs.

2.2 MCU

This section describes some critical features and operations supported by the enhanced MCU.

Figure 2-2 shows the overall structure of the MCU block. In addition to the enhanced MCU core, we have added the following circuits,

●A DSP accelerator cooperates with MCU to process the complex algorithms

●Timer: A number of timers are available to generate different clocks

●Clock Manager: To control various clocks under different operation conditions of the system

Figure 2-2 MCU Block Diagram

Modes

2.3 Operation

FT7681 offers following three modes:

●Active Mode

When in this mode, FT7681 actively scans the panel. The default scan rate is 100 frames per second. The host processor can configure it to speed up or to slow down.

●Monitor Mode

In this mode, FT7681 scans the panel at a reduced speed. The default scan rate is 25 frames per second and the host processor can increase or decrease this rate. In this mode, most algorithms are stopped. A simpler algorithm is being executed to determine if there is a touch or not. When a touch is detected, FT7681 shall enter the Active mode immediately to acquire the touch information quickly. During this mode, the serial port is closed and no data shall be transferred with the host processor.

●Hibernate Mode

In this mode, the chip is set in a power down mode. It shall only respond to the “RESET” signal from the host processor. The chip therefore consumes very little current, which help prolong the standby time for the

portable devices.

2.4 Host Interface

Figure 2-3 shows the interface between a host processor and FT7681. This interface consists of the following

three sets of signals:

● Serial Interface

● Interrupt from FT7681 to the Host ● Reset Signal from the Host to FT7681

Figure 2-3 Host Interface Diagram

The serial interface of FT7681 is I2C. The detail of the interface is described in detail in Section 2.5. The interrupt signal (/INT) is used for FT7681 to inform the host that data are ready for the host to receive. The /RST signal is used for the host to wake up FT7681 from the Hibernate mode. After resetting, FT7681 shall enter the Active mode.

2.5 Serial Interface

FT7681 supports the I2C interfaces, which can be used by a host processor or other devices. The I2C is always configured in the Slave mode. The data transfer format is shown in Figure 2-4.

Figure 2-4 I2C Serial Data Transfer Format

Figure 2-5 I2C master write, slave read

Host

Figure 2-6 I2C master read, slave write

Table 2-1 lists the meanings of the mnemonics used in the above figures.

Table 2-1 Mnemonics Description

Mnemonics

Description

I2C Start or I2C Restart

A[6:0] Slave address

R/ W

READ/WRITE bit, ‘1’ for read, ‘0’for write

A(N) ACK(NACK) bit P

STOP: the indication of the end of a packet (if this bit is missing, S will indicate the

end of the current packet and the beginning of the next packet)

I2C Interface Timing Characteristics is shown in Table 2-2.

Table 2-2 I2C Timing Characteristics Parameter

Min Max Unit SCL frequency

10 400

KHz Bus free time between a STOP and START condition 4.7 us Hold time (repeated) START condition 4.0 us Data setup time

250 ns Setup time for a repeated START condition 4.7 us Setup Time for STOP condition 4.0

3 ELECTRICAL SPECIFICATIONS

3.1

Absolute Maximum Ratings

Table 3-1 Absolute Maximum Ratings

Item

Symbol Value Unit Note Power Supply Voltage 1

VDDA - VSSA

-0.3 ~ +3.6

1, 2

Power Supply Voltage 2 VDD3 – VSS -0.3 ~ +3.6 V 1, 3 I/O Digital Voltage IOVCC 1.8~3.6 V 1 Operating Temperature Topr -40 ~ +85℃ 1

Storage Temperature Tstg -55 ~ +150 ℃ 1

Notes

1. If used beyond the absolute maximum ratings, FT7681 may be permanently damaged. It is strongly recommended that the device be used within the electrical characteristics in normal operations. If exposed to

the condition not within the electrical characteristics, it may affect the reliability of the device.

2. Make sure VDDA (high) ≥VSSA (low)

3. Make sure VDD (high) ≥VSS (low)

3.2 DC

Characteristics

Table 3-2 DC Characteristics

Notes: This consumption data is intended for design guidance only. Actual current will depend on the par-

ticular sensor design and firmware options.

Item Symbol Unit Test Condition Min. Typ. Max. Note

Input high-level voltage VIH V 0.7 x IOVCC-- IOVCC

Input low -level voltage VIL V -0.3 -- 0.3 x IOVCC

Output high -level voltage VOH V IOH=-0.1mA 0.7 x IOVCC-- --

Output low -level voltage VOL V IOH=0.1mA -- -- 0.3 x IOVCC

I/O leakage current ILI uA Vin=0~VDDA -1 --

Current consumption

（Normal operation mode）

Iopr mA

VDDA=VDD3 = 2.8V

Ta=25℃

MCLK=24MHz

-- 11.00 --

Current consumption

（Monitor mode）

Imon mA

VDDA=VDD3 = 2.8V

Ta=25℃

MCLK=24MHz

0.87

Current consumption

（Sleep mode）

Islp uA

VDDA=VDD3 = 2.8V

Ta=25℃

MCLK=24MHz

78.8

-- Step-up output voltage VDD5 V VDDA

=VDD3

= 2.8V 0.25

Power Supply voltage VDDA

VDD3

V 2.8 -- 3.6

3.3 AC Characteristics

AC Characteristics of Oscillators

Item

Symbol Unit Test Condition

Min.

Typ.

Max.

Note

OSC clock 1 fosc1

MHz

VDD3 = 2.8V; Ta=25℃

49 50 51

Table 3-3 AC Characteristics of TX & RX

Item

Symbol Test Condition

Min Typ Max Unit Note

TX acceptable clock ftx 100 150 400 KHz TX output rise time Ttxr -- TBD -- nS TX output fall time Ttxf -- TBD -- nS RX input voltage Trxi

1.2

TBD

1.6

3.4 I/O Ports Circuits

Figure 3-1 General Purpose In/Out Port Circuit.

The input/output property can be configured via firmware setting. The firmware can also control its output behavior as push-pull or as open-drain that SDA of I2C interface is required.

Figure 3-2 Reset Input Port Circuits

Sequence

ON/Reset

3.5 POWER

Reset should be pulled down to be low before powering on and powering down. I2C shouldn’t be used by

other devices during Reset time after VDD powering on (Trtp). INT signal will be sent to the host after in-itializing all parameters and then start to report points to the host. If Power is down, the voltage of supply must be below 0.3V and Tpdt is more than 1ms.

P o w e r

Figure 3-3 Power on time

P o w e r

0.3V

Figure 3-4 Power Cycle requirement

VDD INT I2C

Reset Tvdr

Figure 3-5 Power on Sequence

Reset time must be enough to guarantee reliable reset, the time of starting to report point after resetting approach to the time of starting to report point after powering on.

P o w e r I N T I 2C

R E S E T

Figure 3-6 Reset Sequence

Table 3-5 Power on/Reset Sequence Parameters

Parameter

Description

Min Max Units Tris Rise time from 0.1VDD to 0.9VDD

-- 5 ms Tpdt Time of the voltage of supply being below 0.3V 5 -- ms

Trtp Time of resetting to be low before powering on 100 -- μs

Tpon Time of starting to report point after powering on 200 -- ms Tvdr Reset time after VDD powering on

1 -- ms Trsi Time of starting to report point after resetting 200 -- ms Trst Reset time

END OF DATASHEET