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64 LEDs, I²C Interfaced LED Driver with Keyscan
1 General Description
nt. LED brightness can be controlled by analog or digital means. need for continuous device reprogramming. can be used to trigger an interrupt. nal clock is also supported. Figure 1. AS1115 - Typical Application Diagram
2 Key Features
3 Applications
4 Pinout
Figure 2. Pin Assignments (Top View) Table 1. Pin Descriptions SDA 1 22 Serial-Data I/O . Open drain digital I/O I²C data pin. cathode. Keyscan detection optional, but must be polled by the µProzessor. KEYA 11 8 Keyscan Input. Keyscan lines for key readback. Can be used for selfxaddressing. KEYB 12 9 Keyscan Input. Keyscan lines for key readback. 4 11 Serial-Clock Input . 3.4MHz maximum rate. IRQ 24 21 Interupt Request Output . Open drain pin. point drive that source current to the display. VDD 19 16 Positive Supply Voltage . Connect to +2.7 to +5.5V supply. circuitxboard ground plane to maximize power dissipation.
www.austriamicrosystems.com/LEDxDriverxICs/AS1115 Revision 1.08 3 x 25 AS1115 Datasheet x Absolute Maximum Ratings
5 Absolute Maximum Ratings
Stresses beyond those listed in Ta ble 2 may cause permanent damage to the device. These are s tress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in Section 6 Electrical Characteristics on page 4 is not implied. Exp osure to absolute maximum rating conditions for extended periods may affect device reliability. T able 2. Absolute Maximum Ratings Parameter Min Max Units Comments Electrical Parameters VDD to GND x0.3 7 V All other pins to GND x0.3 7 or VDD + 0.3 V DI G0:DIG7 Sink Current 500 mA SEGA:SEGG, SEGDP Sink Current 100 mA Input Current (latchxup immunity) x100 100 mA Norm: JEDEC 78 Electrostatic Discharge Electrostatic Discharge HBM +/x 1 kV Norm: MIL 883 E method 3015 Thermal Information Thermal Resistance Θ JA 88 °C/W on PCB, QSOPx24 package 30.5 °C/W on PCB, TQFN(4x4)x24 package Temperature Ranges and Storage Conditions Junction Temperature +150 ºC Storage Temperature Range x55 +150 ºC Package Body Temperature +260 ºC The reflow peak soldering temperature (body temperature) specified is in accordance with IPC/JEDEC J-STD- 020“Moisture/Reflow Sensitivity Classification for Non- Hermetic Solid State Surface Mount Devices”. The lead finish for Pbxfree leaded packages is matte tin (100% Sn). Humidity nonxcondensing 5 85 % Moisture Sensitive Level 1 Represents a max. floor life time of unlimited ams AG Technical content still valid
6 Electrical Characteristics
parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality Control) methods. Table 4. Logic Inputs/Outputs Characteristics
www.austriamicrosystems.com/LEDxDriverxICs/AS1115 Revision 1.08 5 x 25 AS1115 Datasheet x Electrical Characteristics Note: The Min / Max values of the Timing Characteristics are guaranteed by design. F igure 3. Timing Diagram T able 5. Timing Characteristics (C B = 550pF (max) on each Bus Line) Symbol Parameter Conditions Min Typ Max Unit fSCL SCL Frequency 1 M Hz tBUF Bus Free Time Between STOP and START Co nditions 500 ns tHOLDSTART Hold Time for Repeated ST ART Condition 260 ns tLOW SCL Low Period 50 0 ns tHIGH SCL High Period 26 0 ns tSETUPSTART Setup Time for Repeated ST ART Condition 260 ns tSETUPDATA Data Setup Time 50 n s tRISE SDA + SCL Rise Time 12 0 ns tFALL SDA + SCL Fall Time 12 0 ns tSETUPSTOP STOP Condition Setup Time 26 0 ns tSPIKESUP Pulse Width of Spike Suppressed 50 n s Key Readback Debounce Time 20 ms Repeated START SDI SCL STARTSTOP tBUF tLOW tHOLDSTART tHOLDDATA tR tHIGH tF tSETUPDATA tHOLDSTART tSPIKESUP tSETUPSTOP tSETUPSTART ams AG Technical content still valid
7 Typical Operating Characteristics
Figure 6. Segment Current vs. T emperature; Figure 7. Segment Current vs. R SET ;
8 Detailed Description
Figure 16. AS1115 - Block Diagram (QSOP-24 Package)
able the master to generate the STOP condition. x Master Transmitter to Slave Receiver . The first byte transmitted by the master is the slave address, followed by a number of data bytes. The slave returns an acknowledge bit after the slave address and each received byte. a repeated START condition is also the beginning of the next serial transfer, the bus will not be released. hardware after reception of the slave address and direction bit. is input on SCL. START and STOP conditions are recognized as the beginning and end of a serial transfer. ee Figure 20) is the first byte received following the START condit ion from the master device. Figure 20. I²C Device Address Byte x The default slave address is factoryxset to 0000000. maximum of four devices with the same prexset code can therefore be connected on the same bus at one time. A short writes a logical “0” whereas an open writes a logical “1” as address bit (see Figure 26 on page 15). a write operation is selected. address code, and the R/W bit, the slave device outputs an acknowledge signal on the SDA line.
- A single command for self addressing will update all connected AS1115. This command has to be done after startup or every time the
debounce time of key registers.
The AS1115 operation, (see Table 6) is determined by a command byte (se e Figure 21 on page 11). Figure 22. Command and Single Data Byte Received Figure 23. Setting the Pointer to a Address Register to select a Data Register for a Read Operation Figure 24. Reading nBytes from AS1115
1 Byte
is time, all registers should be programmed for normal operation. is set to the minimum values. wn Register (see Table 7). During shutdown mode the DigitxRegisters maintain t heir data. ing shutdown mode). For minimum supply current in shutdown mode, logic input should be at GND or VDD (CMOS logic level). used with an external clock, Shutdown Register bit D7 should be set to 1 when writing to the Shutdown Register. ected using a 8xbit address word, and communication is done via the I²C interface. Table 6. Register Address Map
The Shutdown Register controls AS1115 shutdown mode. bit D1 corresponds to digit 1 and so on). Table 9 lists some examples of the possible settings for the Decode Enable Register bits. Note: A logic high enables decoding and a logic low bypasses the decoder altogether. When decode mode is used, the decoder looks only at the lowerxnibble (bits D3:D0) of the data in the DigitxRegisters, disregarding bits D6:D4. exB font; Table 10 lists the HEX font. CodexB/HEX decode for digits 0,2,5.
Figure 25. Standard 7-Segment LED Intensity Control and Inter-Digit Blanking The decimal point can be enabled with every character by setting bit D7 = 1. The decimal point can be enabled with every character by setting bit D7 = 1.
www.austriamicrosystems.com/LEDxDriverxICs/AS1115 Revision 1.08 15 x 25 AS1115 Datasheet x Detailed Description I²C Self Addressing If this feature is used, 2 of the 16 key readback nodes can be left open or shorted for selfxaddressing. This is done with KEYA together with SE GG (A0) and SEGF (A1). This two nodes cannot be used for keyxreadback in this case. After startup all devices have the predefined address 0000000. A single command for self addressing will update all connected AS1115. This command has to be done after startup or every time the AS1115 gets disconnected from the supply. The I²C address definition must be done with fixed connection, since I²C detection is excluded from debounce time of key registers.geht Note: A short writes a logical “0” whereas an open writes a logical “1” as address bit (see Figure 26). Fig ure 26. Address Coding Keyscan Register These two registers contain the result of the keyscan input of the 16 keys. To ensure proper results the data in these registers are updated only if the logic data scanned is stable for 20ms (debounce time). A change of the data stored within these two registers is indicated by a logic low on the IRQ pin. The IRQ is highximpedance if a read operation on the key scan registers is started. Note: If I²C self addressing is used segment G&F of KEYA is used for the two LSB of the I²C address. In this case these two nodes cannot be used as a key. Additionally the debounce time is disabled for these two bits. The data within the keyscan register is updated continuously during every cycle (1/10 of refresh rate). Therefore, to get a valid readx back of keys it is recommended to read out the keyscan registers immediately after the IRQ is triggered. A short writes a logical “0” whereas an open writes a logical “1” as keyscan register bit. Note: If the blink_en bit (bit D4 in the Feature Register 0x0E) is set to ‘1’, the keyscan is not returning a valid value. T able 11. No-Decode Mode Data Bits and Corresponding Segment Lines D7 D6 D5 D4 D3 D2 D1 D0 Corresponding Segment Line DP A B C D E F G T able 12. Self Addressing Register (Address (HEX) = 0x2D)) D7 D6 D5 D4 D3 D2 D1 D0 Factoryxset IC address X X X X X X X 0 Userxset IC address X X X X X X X 1 T able 13. LED Diagnostic Register Address Register HEX Address Segment Key D7 D6 D5 D4 D3 D2 D1 D0 0x1C KEYA DP A B C D E F G0x1D KEYB ams AG Technical content still valid
www.austriamicrosystems.com/LEDxDriverxICs/AS1115 Revision 1.08 16 x 25 AS1115 Datasheet x Detailed Description Display-Test Mode The AS1115 can detect open or shorted LEDs. Readout of either open LEDs or short LEDs is possible, as well as a OR relation of open and sh ort. Note: All settings of the digitx and controlxregisters are maintained. LED Diagnostic Registers These eight registers contain the result of the LED open/short test for the individual LED of each digit. N o te: If one or more short occures in the LED array, detection of individual LED fault could become ambiguous. Intensity Control Register (0x0A) The brightness of the display can be controlled by digital means using the Intensity Control Registers and by analog means using RSET (see Se lecting RSET Resistor Value and Using External Drive rs on page 19). The intensity can be controlled globally for all di gits, or for each digit individually. The global intensity command will write intensity data to all four individual brightness registers, while the individual intensity command will only write to the associated individual intensity register. T able 14. Testmode Register Summary D7 D6 D5 D4 D3 D2 D1 D0 X RSET_short RSET_open LED_global LED_test LED_open LED_short DISP_test T able 15. T estmode Register Bit Description (Address (HEX) = 0x0F)) Addr: 0x0F Address Bit Bit Name Default Access D7:D0 D0 DISP_test 0 W Optical display test. (Testmode for external visual test.) 0: Normal operation; 1: Run display test (All digits are tested independently from scan limit & shutdown register.) D1 LED_short 0 W Starts a test for shorted LEDs. (Can be set together with D2) 0: Normal operation; 1: Activate testmode D2 LED_open 0 W Starts a test for open LEDs. (Can be set together with D1) 0: Normal operation; 1: Activate testmode D3 LED_test 0 R Indicates an ongoing open/short LED test 0: No ongoing LED test; 1: LED test in progress D4 LED_global 0 R Indicates that the last open/short LED test has detected an error 0: No error detected; 1: Error detected D5 RSET_open 0 R Checks if external resistor RSET is open RSET correct; 1: RSET is open RSET_short 0 R Checks if external resistor RSET is shorted RSET correct; 1: RSET is shorted D7 0 x Not used T able 16. LED Diagnostic Register Address Register HEX Address Segment Register HEX Address Segment Digit D7 D6 D5 D4 D3 D2 D1 D0 Digit D7 D6 D5 D4 D3 D2 D1 D0 0x14 DIG0 DP A B C D E F G 0x18 DIG4 DP A B C D E F G0x15 DIG1 0x19 DIG5 0x16 DIG2 0x1A DIG6 0x17 DIG3 0x1B DIG7 ams AG Technical content still valid
Display brightness is controlled by an integrated pulsexwidth modulator which is controlled by the lowerxnibble of the Intensity Control Register. e modulator scales the average segmentxcurrent in 16 steps from a maximum of 15/16 down to 1/16 of the peak current set by RSET . where N is the number of digits. Note: To avoid differences in brightness this register should not be used to blank parts of the display (leading zeros). Table 18. Intensity Register Address
www.austriamicrosystems.com/LEDxDriverxICs/AS1115 Revision 1.08 18 x 25 AS1115 Datasheet x Detailed Description Feature Register (0x0E) The Feature Register is used for enabling various features including switching the device into external clock mode, applying an external reset, se lecting codexB or HEX decoding, enabling or disabling blinking, setting the blinking rate, and resetting the blink timing. Note: At powerxup the Feature Register is initialized to 0. T able 20. Feature Register Summary D7 D6 D5 D4 D3 D2 D1 D0 blink_ start sync blink_ freq_sel blink_en NU decode_sel reg_res clk_en T able 21. Feature Register Bit Descriptions (Address (HEX) = 0xXE) Addr: 0xXE Feature Register Enables and disables various device features. Bit Bit Name Default Access Bit Description D0 clk_en 0 R/W External clock active. 0 = Internal oscillator is used for system clock. 1 = Pin CLK of the serial interface operates as system clock input. D1 reg_res 0 R/W Resets all control registers except the Feature Register. 0 = Reset Disabled. Normal operation. 1 = All control registers are reset to default state (except the Feature Register) identically after powerxup. Note: The Digit Registers maintain their data. D2 decode_sel 0 R/W Selects display decoding for the selected digits (Table 8 on page 13). 0 = Enable CodexB decoding (see Table 9 on page 14). 1 = Enable HEX decoding (see Table 10 on page 14). D3 N U Not used D4 blink_en 0 R/W Enables blinking. 0 = Disable blinking. 1 = Enable blinking. D5 blink_freq_sel 0 R/W Sets blink with low frequency (with the internal oscillator enabled): 0 = Blink period typically is 1 second (0.5s on, 0.5s off). 1 = Blink period is 2 seconds (1s on, 1s off). D6 sync 0 R/W Synchronizes blinking on the rising edge of pin LD/CS. The multiplex and blink timing counter is cleared on the rising edge of pin LD/CS. By setting this bit in multiple devices, the blink timing can be synchronized across all the devices. D7 blink_start 0 R/W Start Blinking with display enabled phase. When bit D4 (blink_en) is set, bit D7 determines how blinking starts. 0 = Blinking starts with the display turned off. 1 = Blinking starts with the display turned on. ams AG Technical content still valid
www.austriamicrosystems.com/LEDxDriverxICs/AS1115 Revision 1.08 19 x 25 AS1115 Datasheet x Typical Application
9 Typical Application
lecting R SET Resistor Value and Using External Drivers Brightness of the display segments is controlled via RSET . The current that flows into ISET defines the current that flows through the LEDs. Se gment current is about 200 times the current in ISET . Typical values for RSET for different segment currents, operating voltages, and LED voltx ag e drop (VLED ) are given in Ta ble 22 & Table 23. The maximum current the AS1115 can drive is 47mA. If higher currents are needed, exterx nal drivers must be used, in which case it is no longer necessary that the devices drive high currents. Note: The display brightness can also be logically controlled (see Intensity Control Register (0x0A) on page 16). Calculating Power Dissipation The upper limit for power dissipation (PD) for the AS1115 is determined from the following equation: PD = (VDD x 5mA) + (VDD - VLED)(DUTY x ISEG x N) (E Q 1) Where: VDD is the supply voltage. DU TY is the duty cycle set by intensity register (page 17). N is the number of segments driven (worst case is 8) VLED is the LED forward voltage ISEG = segment current set by RSET Di ssipation Example: ISEG = 40mA, N = 8, DUTY = 15/16, VLED = 2.2V at 40mA, VDD = 5V (E Q 2) PD = 5V(5mA) + (5V - 2.2V)(15/16 x 40mA x 8) = 0.865W (EQ 3) Thus, for a TQFN(4x4)x24 package Θ JA = +30.5°C/W, the maximum allowed TAMB is given by: TJ,MAX = TAMB + PD x Θ JA = 150° C = TAMB + 0.865W x 30.5° C/W (E Q 4) In this example the maximum ambient temperature must stay below 123.61°C. ISEG (mA) V LED V LED V LED VDD = 2.7V 5kΩ 4.4kΩ VDD = 3.3V 6.7kΩ 6.4kΩ 5.7kΩ VDD = 3.6V 7.5kΩ 7.2kΩ 6.6kΩ 5.5kΩ T able 23. RSET vs. Segment Current and LED Forward Voltage, V DD = 4.0V & 5.0V ISEG (mA) V LED V LED VDD = 4.0V VDD = 5.0V ams AG Technical content still valid
Figure 29. QSOP-24 Marking
Figure 31. QSOP-24 Package
Figure 32. TQFN(4x4)-24 Package
www.austriamicrosystems.com/LEDxDriverxICs/AS1115 Revision 1.08 24 x 25 AS1115 Datasheet x Ordering Information The devices are available as the standard products shown in T able 25. No te: All products are RoHS compliant and austriamicrosystems green. Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect Technical Support is found at http://www.austriamicrosystems.com/TechnicalxSupport For further information and requests, please contact us mailto:sales@austriamicrosystems.com or find your local distributor at http://www.austriamicrosystems.com/distributor T able 25. Ordering Information Ordering Code Marking Description Delivery Form Package AS1115xBSST AS1115 64 LEDs, I²C Interfaced LED Driver with Keyscan Tape and Reel QSOPx24 AS1115xBQFT AS1115 Tape and Reel TQFN(4x4)x24 ams AG Technical content still valid
www.austriamicrosystems.com/LEDxDriverxICs/AS1115 Revision 1.08 25 x 25 AS1115 Datasheet Copyrights Copyright © 1997x2012, austriamicrosystems AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, AustriaxEurope. Trademarks Registered ®. A ll rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. All products and companies mentioned are trademarks or registered trademarks of their respective companies. Disclaimer Devices sold by austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. a ustriamicrosystems AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. austriamicrosystems AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with austriamicrosystems AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical lifexsupport or lifexsustaining equipment are specifically not recommended without additional processing by austriamicrosystems AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location. The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However, austriamicrosystemsAG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of austriamicrosystemsAG rendering of technical or other services. Contact Information Headquarters a ustriamicrosystems AG Tobelbaderstrasse 30 Ax8141 Unterpremstaetten, Austria Tel: +43 (0) 3136 500 0 Fax: +43 (0) 3136 525 01 For Sales Offices, Distributors and Representatives, please visit: http://www.austriamicrosystems.com/contact ams AG Technical content still valid