A6282 16-Channel Constant-Current LED Driver Features and Benefits Description ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ The A6282 device is designed for LED display applications. This CMOS device includes an input shift register, accompanying data latches, and 16 MOS constant current sink drivers. 16 constant-current outputs, up to 50 mA each LED output voltage up to 12 V 3.0 to 5.5 V logic supply range Schmitt trigger inputs for improved noise immunity Power-On Reset (POR), all register bits = 0 Low-power CMOS logic and latches High data input rate: 30 MHz Output current accuracy: between channels < ±3% and between ICs ±7%, over the full operating temperature range ▪ Internal UVLO and thermal shutdown (TSD) circuitry The CMOS shift registers and latches allow direct interfacing with microprocessor-based systems. With a 3.3 or 5 V logic supply, typical serial data input rates can reach up to 30 MHz. The LED drive current level can be set by a single external resistor, selected by the application designer. A serial data output permits cascading of multiple devices in applications requiring additional drive lines. The A6282 is available in two 24-terminal packages: QFN (package ES) and TSSOP (LP), which have an exposed thermal pad. Both packages are lead (Pb) free with 100% matte tin leadframe plating. Packages: 24-pin TSSOP with exposed thermal pad (Package LP) Applications include the following: ▪ Monocolor, multicolor, or full-color LED display ▪ Monocolor, multicolor, or full-color LED signboard ▪ Display backlighting ▪ Multicolor LED lighting 24-contact QFN 4 mm × 4 mm × 0.75 mm (Package ES) Not to scale Typical Application VLED 10 μF 10 μF SDI Controller SDI CLK CLK LE LE OE OE OUT0 OUT15 SDI SDO VDD VDD 100 nF A6282 GND REXT IC 1 CLK LE OUT15 SDO VDD GND OE VDD 100 nF A6282 REXT IC 2 Cascaded A6282 devices 6282-DS, Rev. 4 OUT0 A6282 16-Channel Constant-Current LED Driver Selection Guide Part Number Package Packing A6282EESTR-T 4 mm × 4 mm QFN, 24 pins, exposed thermal pad 1500 pieces per 7-in. reel A6282ELPTR-T TSSOP, 24 pins, exposed thermal pad 4000 pieces per 13 in. reel Absolute Maximum Ratings Characteristic Supply Voltage* Symbol Notes Rating Unit VDD –0.3 to 5.5 V OUTx Current (any single output) IO 60 mA Input Voltage Range* VI –0.3 to VDD + 0.3 V –0.3 to 13.2 V LED Load Supply Range* VOE, VLE, VCLK, VSDI VLED ESD Rating Operating Temperature Range (E) Junction Temperature Storage Temperature Range HBM (JEDEC JESD22-A114, Human Body Model) 2.0 kV CDM (JEDEC JESD22-C101, Charged Device Model) 1.0 kV –40 to 85 °C TA TJ(max) 150 °C Tstg –55 to 150 °C *With respect to ground. Thermal Characteristics Characteristic Package Thermal Resistance Test Conditions1 ES package, 4-layer PCB based on JEDEC standard LP packge, 4-layer PCB based on JEDEC standard Symbol RθJA Value 37 28 Units °C/W °C/W *Additional thermal information available on the Allegro website. Allowable Package Power Dissipation (W) 5.0 4.0 Pa ck ag e 3.0 Pa ck LP ,R QJ A ag eE S, 28 °C /W QJ 2.0 = R A =3 7° C/ W 1.0 0 25 50 75 100 125 Ambient Temperature (°C) 150 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 A6282 16-Channel Constant-Current LED Driver Functional Block Diagram VDD UVLO and TSD SDI SDO Serial - Parallel Shift Register CLK OE Control Logic Block LE Latches Output Control Drivers REXT IO Regulator Exposed Pad (ET and LP packages) OUT15 GND OUT0 OUT1 VLED Inputs and Outputs Equivalent Circuits Resistor values are equivalent resistance and not tested VDD CLK, SDI, LE, Ō¯Ē 500 Ω VDD 10 Ω SDO Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 A6282 16-Channel Constant-Current LED Driver Pin-out Diagrams SDO 19 OUT11 20 OUT12 21 OUT13 22 OUT14 23 OUT15 24 OE Top-down views 18 OUT10 1 GND 1 24 VDD SDI 2 23 REXT CLK 3 22 SDO LE 4 21 OE 17 OUT9 OUT0 5 16 OUT8 OUT1 6 4 15 OUT7 OUT2 7 18 OUT13 SDI 5 14 OUT6 OUT3 8 17 OUT12 CLK 6 13 OUT5 OUT4 9 16 OUT11 OUT5 10 15 OUT10 OUT6 11 14 OUT9 OUT7 12 13 OUT8 OUT4 12 OUT3 11 9 OUT1 OUT2 10 8 GND PAD 7 3 LE 2 VDD OUT0 REXT ES Package 20 OUT15 PAD 19 OUT14 LP Package Terminal List Table CLK GND LE Number ES LP 6 3 4 1 7 4 ¯¯Ē¯ Ō 24 21 OUT0 OUT1 OUT2 OUT3 OUT4 OUT5 OUT6 OUT7 OUT8 OUT9 OUT10 OUT11 OUT12 OUT13 OUT14 OUT15 PAD REXT SDI SDO VDD 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 – 2 5 1 3 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 – 23 2 22 24 Name Description Clock; data shift clock input terminal Logic supply ground and load supply ground Latch Enable input terminal Output Enable input terminal, active low (when Ō ¯¯Ē¯ = high, all OUTx outputs are forced off; when Ō ¯¯Ē¯ = low, on/off status of OUTx outputs is controlled by the state of the latches Constant current outputs Exposed pad for enhanced thermal dissipation; not connected internally, connect to GND Reference current terminal; sets output current for all channels Serial Data In terminal Serial Data Out terminal Logic Supply terminal Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 A6282 16-Channel Constant-Current LED Driver ELECTRICAL CHARACTERISTICS at TA1 = 25°C, VDD = 3.0 to 5.5 V, unless otherwise noted Characteristic Logic Supply Voltage Range LED Load Supply Output Voltage Undervoltage Lockout Output Current Output Current Shift Output to Output Matching Error3 Output Current Regulation Output Leakage Current Logic Input Voltage Logic Input Voltage Hysteresis Logic Input Current SDO Voltage Supply Current4 Symbol Test Conditions Operating VDD VLED Operating VDD 0 → 5.0 V VDD(UV) VDD 5 → 0.0 V VDD = 4.5 to 5.5 V, VDS(x) = 1 V, REXT = 374 VDD = 3.0 to 3.6 V, VDS(x) = 1 V, REXT = 374 IO VDD = 4.5 to 5.5 V, VDS(x) = 1 V, REXT = 910 VDD = 3.0 to 3.6 V, VDS(x) = 1 V, REXT = 910 VDD = 5.5 V, VDS(x) = 1 V, REXT = 910 Ω, %∆IO TA = 25°C; between one output on and all outputs on VDS = 1 V, REXT = 374 , all outputs on Err VDS = 1 V, REXT = 910 , all outputs on VDD = 5.5 V, VDS(x) = 1 to 3 V, REXT = 374 , all outputs on VDD = 5.5 V, VDS(x) = 1 to 3 V, REXT = 910 , all outputs on %IO(reg) VDD = 3.6 V, VDS(x) = 1 to 3 V, REXT = 374 , all outputs on VDD = 3.6 V, VDS(x) = 1 to 3 V, REXT = 910 , all outputs on IDSS VOH = 12 V VIH VIL VIhys All digital inputs II All digital inputs IOL = 1 mA VOL VOH IOH = –1 mA REXT = 3.8 k, VOE = 5 V IDD(OFF) REXT = 910 , VOE = 5 V REXT = 374 , VOE = 5 V All outputs on, REXT = 910 , VO = 1 V, data transfer 30 MHz IDD(ON) All outputs on, REXT = 374 , VO = 1 V, data transfer 30 MHz Min. 3.0 – 2.5 2.3 Typ.2 5.0 – 2.7 2.5 Max. 5.5 12.0 2.9 2.7 Unit V V V V 47.4 51.1 54.5 mA 46.5 50.1 53.5 mA 19.8 21.4 22.8 mA 19.5 21.0 22.4 mA – – ±1 % – – +1.0 +1.0 +3.0 +3.0 % % – 1.7 3 %/V – 2.4 4 %/V – 1.2 2 %/V – 1.8 3 %/V – 0.8×VDD GND 250 –1 – VDD – 0.5 – – – – – – – – – – – – – 0.5 VDD 0.2×VDD 900 1 0.5 – 6 16 40 μA V V mV μA V V mA mA mA – – 20 mA – – 45 mA Continued on the next page… Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 A6282 16-Channel Constant-Current LED Driver ELECTRICAL CHARACTERISTICS (continued), at TA1 = 25°C, VDD = 3.0 to 5.5 V, unless otherwise noted Characteristic Thermal Shutdown Temperature Thermal Shutdown Hysteresis Reference Voltage at External Resistor REXT Symbol Test Conditions TJTSD Temperature increasing TJTSDhys VEXT REXT = 374 Min. – – Typ.2 165 15 Max. – – Unit °C °C – 1.21 – V 1Tested at 25°C. Specifications are assured by design and characterization over the operating temperature range of –40°C to 85°C. data are for initial design estimations only, and assume optimum manufacturing and application conditions. Performance may vary for individual units, within the specified maximum and minimum limits. 3Err = (I (min or max) – I (av)) / I (av). I (av) is the average current of all outputs. I (min or max) is the output current with the greatest O O O O O difference from IO(av). 4Recommended operating range: V = 1.0 to 3.0 V. O 2Typical SWITCHING CHARACTERISTICS at TA1 = 25°C, VDD = VIH = 5.0 V, VDS = 1 V, VIL = 0 V, REXT = 910 Ω, IO = 21.4 mA, VL = 2 V, RL = 51 Ω, CL = 15 pF (see also Timing Diagrams section) Characteristic Symbol Test Conditions Clock Frequency fCLK CLK Clock Frequency (cascaded devices) fCLKC Min. Typ.2 Max. Unit – – 30 MHz CLK – – 25 MHz Clock Pulse Duration twh0 CLK = high 16 – – ns LE Pulse Duration twh1 LE = high 20 – – ns tsu0 SDI to CLK↑ 10 – – ns tsu1 CLK↑ to LE↑ 10 – – ns th0 CLK↑ to SDI 10 – – ns th1 LE↓ to CLK↑ 10 – – ns tr0 SDO, 10/90% points (measurement circuit A) – – 16 ns tr1 OUTx, VDD = 5 V,10/90% points (measurement circuit B) – 10 30 ns tf0 SDO, 10/90% points (measurement circuit A) – – 16 ns tf1 Setup Time Hold Time Rise Time Fall Time Propagation Delay Time Output Enable Pulse Duration OUTx, VDD = 5 V,10/90% points (measurement circuit B) – 10 30 ns tpd0 CLK↑ to SDO↑↓ (measurement circuit A) – – 30 ns tpd1 ¯¯Ē ¯ ↓ to OUTx↑↓ (measurement circuit B) Ō – – 60 ns tpd2 LE↑ to OUTx↑↓ (measurement circuit B) – – 60 ns (see Timing Diagrams section) 60 – – ns tw(OE) 1Tested at 25°C. Specifications are assured by design and characterization over the operating temperature range of –40°C to 85°C. data are for initial design estimations only, and assume optimum manufacturing and application conditions. Performance may vary for individual units, within the specified maximum and minimum limits. 2Typical Parameter Measurement Circuits VL A6282 A6282 RL SDO OUTx CL 15 pF (A) Circuit for tf0 , tpd0 , and tr0 (B) Circuit for tf1 , tpd1 , tpd2 , and tr1 . Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 A6282 16-Channel Constant-Current LED Driver Timing Diagrams Normal Operation t wh0 CLK t su0 t h0 SDI t pd0 t 10% SDO t t r0 f0 90% 50% t wh1 su1 LE Low = All Outputs Enabled OE t pd2 H ig h = O u tp u t o n OUTx (current) Low = Output off Disabling Outputs t w (OE) OE 50% 50% t pd1 OUTx (current) t pd1 t f1 t r1 90% 50% 10% Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 A6282 16-Channel Constant-Current LED Driver Operating Characteristics Channel Maximum Constant Output Current versus External Reference Resistance Channel Output Current versus Output Voltage VDD = 5.0 V 60 50 45 50 35 4.5 to 5.0 3.0 to 3.6 IO (mA) IO(max) (mA) VDD (V) 40 REXT = 470 Ω 40 30 30 25 REXT = 910 Ω 20 20 15 10 10 5 0 0.3 0 1.0 2.0 3.0 4.0 5.0 0 0.3 0.6 0.9 1.2 REXT (kΩ) 1.5 1.8 2.1 2.4 2.7 3.0 VDS (V) Input-Output Truth Table Serial Data Input (SDI) Shift Register Contents Clock Input (CLK) I0 I1 I2 … I15 Serial Data Out (SDO) H H R0 R1 … R15 R14 L L R0 R1 … R15 R14 X R0 R1 R2 … R15 R15 X X X X … P0 P1 P2 … P15 Latch Enable Input (LE) X L P15 H Latch Contents I0 I1 I2 … R0 R1 R2 … P15 I15 X X … Output Contents I15 L (Outputs on) P15 I0 I1 I2 … R15 P0 P1 P2 … X Output Enable Input ¯¯Ē¯ ) ( Ō X H (Outputs off) P0 P1 P2 … H H H … H L = Low logic (voltage) level, H = High logic (voltage) level, X = Don’t care, P = Present state, R = Previous state Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 A6282 16-Channel Constant-Current LED Driver Functional Description Normal Operation Serial data present at the SDI (Serial Data In) input is transferred to the shift register on the transition from logic 0 to logic 1 of the CLK (Clock) input pulse. On succeeding CLK pulses, the register shifts data towards the SDO (Serial Data Out) output. The serial data must appear at the input prior to the rising edge of the CLK waveform. Data present in any register is transferred to the respective latch when the LE (Latch Enable) input is high (serial-to-parallel conversion). The latches continue to accept new data as long as LE is held high (level triggered). Applications where the latches are bypassed (LE tied high) ¯ (Output Enable) input be high during serial require that the Ō¯¯Ē ¯ is high, the output sink drivers are disabled data entry. When Ō¯¯Ē (off). The data stored in the latches is not affected by the state ¯ . With Ō¯¯Ē ¯ active (low), the outputs are controlled by the of Ō¯¯Ē state of their respective latches. Setting Maximum Channel Current The maximum output current per channel is set by a single external resistor, REXT, which is placed between the REXT pin and GND. The voltage on REXT, VEXT, is set by an internal band gap and is 1.21 V, typical. The maximum channel output current can be calculated as: IO(max) = (18483.1/ REXT) + 0.67 , for VDD = 3.0 to 3.6 V , or IO(max) = (18841.2/ REXT) + 0.68 , for VDD = 4.5 to 5.5 V , where REXT is the value of the user-selected external resistor, which should not be less than 374 Ω. A chart of the maximum per channel (OUT0 to OUT15) constant output current, IO(max), at various values of REXT , is shown in the Operating Characteristics section. Undervoltage Lockout The A6282 includes an internal undervoltage lockout (UVLO) circuit that disables the outputs in the event that the logic supply voltage drops below a minimum acceptable level. This feature prevents the display of erroneous information, a necessary function for some critical applications. Upon recovery of the logic supply voltage after a UVLO event, all internal shift registers and latches are set to 0. The A6282 is then in normal mode. Thermal Shutdown Protection If the junction temperature exceeds the threshold temperature, TJTSD , 165°C typical, the outputs will be turned off until the junction temperature cools down through the thermal shutdown hysteresis, 15°C typical. The shift register and output latches register will remain active during a thermal shutdown event. Therefore, there is no need to reset the data in the output latches. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 A6282 16-Channel Constant-Current LED Driver Application Information Load Supply Voltage (VLED) This device is designed to operate with driver voltage drops (VDS) of 1.0 to 3.0V. If higher voltages are dropped across the driver, package power dissipation will increase. To minimize package power dissipation, it is recommended to use the lowest possible load supply voltage, VLED, or to set a series voltage drop, VDROP , according to the following formula: VDROP = VLED – VF – VDS , where VF is the LED forward voltage. For reference, typical LED forward voltages are: LED Type VF (V) White Blue Green Yellow Amber Red Infrared UV 3.5 to 4.0 3.0 to 5.5 1.8 to 2.5 2.0 to 2.5 1.9 to 3.0 1.6 to 2.5 1.2 to 1.8 3.0 to 4.0 1. Place the REXT resistor as close as possible to the REXT pin and GND pin. This will minimize parasitic inductance and capacitance. 2. Use a separate line to the device GND pin for REXT, and separate lines for the decoupling capacitors. The lines should join at ground. This star grounding will improve output load regulation and minimize any chance of oscillation. The REXT ground line should carry only the small current from the internal voltage reference at REXT. The high AC currents flowing through the decoupling capacitors and their resistive and inductive PCB lines cause noise (ground bounce) on the capacitor ground lines. Such noise could disturb the reference voltage at REXT and promote oscillation. Connect the exposed thermal pad of the ES and LP packages to the power ground, along with the decoupling capacitors, and not to the ground line for REXT. 3. Keep the output drive lines (OUT0 through OUT15) away from the REXT pin to avoid coupling of the output signal into the reference for the current sources. Output lines should not run adjacent to the REXT pin or directly under the REXT pin. VDROP = IO× RDROP for a single driver, for a Zener diode (VZ), or for a series string of silicon diodes (approximately 0.7 V per diode) for a group of drivers (these configurations are shown in the figure below). If the available voltage source will cause unacceptable power dissipation and series resistors or diodes are undesirable, a voltage regulator can be used to provide VLED. 4. Use decoupling capacitors on the VDD pin and the LED supply bus. Place the logic decoupling capacitor (0.1 μF, one for each A6282) as close as possible to the VDD pin. Use at least one 10 μF capacitor from the LED supply line to device ground for at least every two A6282s. Pattern Layout To save pins and board space, the A6282 uses one pin for both logic ground and power ground. Therefore, achieving optimal performance requires careful attention to layout. Following the suggestions below will improve the analog performance and logic noise immunity. Package Power Dissipation The maximum allowable package power dissipation based on package type is determined by: VLED VLED VLED VDROP VDROP VDROP VF VF VF VDS VDS VDS Typical application voltage drops 5. Use multilayer boards if possible. PD(max) = (150 – TA) / RJA , where RJA is the thermal resistance of the package, determined experimentally. Power dissipation levels based on the package are shown in the Thermal Characteristics table. The actual package power dissipation is determined by: PD(act) = DC × (VDS × IO× 16) + (VDD× IDD) , where DC is the duty cycle. The value 16 is the maximum number of available device outputs, representing the worst-case scenario (displaying all 16 LEDs). When the load supply voltage, VLED, is greater than 3 to 5 V, and PD(act) > PD(max), an external voltage reducer (VDROP) must be used (figure at left). Reducing DC will also reduce power dissipation. The ES and LP packages contain an exposed thermal pad on the bottom of the package for enhanced heat dissipation. Connect this pad to a large power ground plane using thermal vias. JEDEC documents JESD51-3 and JESD51-5 give suggestions for PCB and thermal via designs. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 A6282 16-Channel Constant-Current LED Driver Package ES, 4 mm x 4 mm, 24-pin QFN with Exposed Thermal Pad 0.30 4.00 ±0.15 1 2 0.50 24 24 0.90 1 2 A 2.10 4.00 ±0.15 4.10 2.10 4.10 25X D SEATING PLANE 0.08 C +0.05 0.25 –0.07 0.75 ±0.05 0.50 C C PCB Layout Reference View For Reference Only (reference JEDEC MO-220WGGD) Dimensions in millimeters Exact case and lead configuration at supplier discretion within limits shown A Terminal #1 mark area B Exposed thermal pad (reference only, terminal #1 identifier appearance at supplier discretion) +0.15 0.40 –0.10 B 2.10 2 1 C Reference land pattern layout (reference IPC7351 QFN50P400X400X80-25W6M) All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances; when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) D Coplanarity includes exposed thermal pad and terminals 24 2.10 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 A6282 16-Channel Constant-Current LED Driver Package LP, 24-pin TSSOP with Exposed Thermal Pad 7.80 ±0.10 4° ±4 24 0.65 0.45 +0.05 0.15 –0.06 B 3.00 4.40 ±0.10 6.40 ±0.20 A 1 6.10 (1.00) 2 4.32 0.25 24X SEATING PLANE 0.10 C +0.05 0.25 –0.06 3.00 0.60 ±0.15 0.65 1.20 MAX 0.15 MAX C SEATING PLANE GAUGE PLANE 1.65 4.32 C PCB Layout Reference View For reference only (reference JEDEC MO-153 ADT) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Terminal #1 mark area B Exposed thermal pad (bottom surface) C Reference land pattern layout (reference IPC7351 TSOP65P640X120-25M); all pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances; when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 12 A6282 16-Channel Constant-Current LED Driver Copyright ©2008-2010, Allegro MicroSystems, Inc. The products described here are manufactured under one or more U.S. patents or U.S. patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. For the latest version of this document, visit our website: www.allegromicro.com Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 13