NE587N

Philips Semiconductors Linear Products Product specification LED decoder/driver NE587 DESCRIPTION The NE587 is a latch/decoder/driver for 7-segment common anode LED displays. The NE587 has a programmable current output up to 50mA which is essentially independent of output voltage, power supply voltage, and temperature. The data (BCD) inputs and LE (latch enable) input are low-loading so that they are compatible with any data bus system. The 7-segment decoding is implemented with a ROM so that alternative fonts can be made available. PIN CONFIGURATIONS N Package D1 D2 LE BI/RBO RBI 1 2 3 4 5 6 7 8 9 18 17 16 15 14 13 12 11 10 VCC f g a b c d e POWER GND FEATURES • Latched BCD inputs • Low loading bus-compatible inputs • Ripple-blanking on leading- and/or trailing-edge zeros APPLICATIONS D3 D0 IP DIG GND D1 Package • Digital panel motors • Measuring instruments • Test equipment • Digital clocks • Digital bus monitoring D1 D2 LE BI/RBO RBI 1 2 3 4 5 20 19 18 17 16 15 14 13 12 11 VCC f g a b NC c d e POWER GND NC 6 D3 D0 IP 7 8 9 DIG GND 10 NOTE: 1. SOL and non-standard pinout. ORDERING INFORMATION DESCRIPTION 20-Pin Plastic Small Outline Large (SOL) Package 18-Pin Plastic Dual In-Line Package (DIP) NOTES: 1. SOL and non-standard pinout TEMPERATURE RANGE 0 to +70°C 0 to +70°C ORDER CODE NE587D1 NE587N DWG # 0172D 0407A ABSOLUTE MAXIMUM RATINGS TA=25°C unless otherwise specified. SYMBOL VCC VIN VOUT PD TA TJ TSTG TSOLD Supply voltage Input voltage (D0-D3, LE, RBI) Output voltage (a-g, RBO) Power dissipation (25°C)1 Ambient temperature range Junction temperature Storage temperature range Soldering temperature (10sec max) PARAMETER RATING -0.5 to +7 -0.5 to +15 -0.5 to +7 1000 0 to 70 150 -65 to +150 300 UNIT V V V mW °C °C °C °C NOTES: 1. Derate power dissipation as indicated N package—95°C/W above 55°C August 31, 1994 530 853-1095 13721 Philips Semiconductors Linear Products Product specification LED decoder/driver NE587 BLOCK DIAGRAM BI/RBO (4) VCC (18) .. RBI (5) D0 D1 D2 D3 (7) (1) (2) (6) DATA LATCHES BCD TO 7-SEGMENT DECODER LE (3) a (15) b (14) IP (8) BANDGAP REFERENCE SEGMENT CURRENT DRIVER c (13) d (12) e (11) GND (9) .. POWER GND (10) f (17) g (16) August 31, 1994 531 Philips Semiconductors Linear Products Product specification LED decoder/driver NE587 DC ELECTRICAL CHARACTERISTICS VCC=4.75 to 5.25V, 0°C < TA < 70°C. Typical values are at VCC=5V, TA=25°C, RP=1kΩ (±1%), unless otherwise specified. SYMBOL VCC VIH VIL VIC PARAMETER Operating supply voltage Input high voltage Input low voltage Input clamp voltage IIN=-12mA, TA=25°C Inputs D0-D3, LE, RBI VIN=2.4V IIH Input high current VIN=15V Input BI (Pin 4) RBI=H VIN=VCC=5.25V VIN=0.4V, Inputs D0-D3 IIL Input low current LE, RBI Input BI VCC=5.25V RBI=H, VIN=0.4V VOL Output low voltage Output RBO IOUT=3.0mA Output RBO VOH IOUT ∆IOUT Output high voltage Output segment “ON” current Output current ratio (all outputs ON) Output segment IOFF ICCO “OFF” current Supply current IOUT=-50µA RBI=H Outputs “a” through “g” VOUT=2.0V With reference to “b” segment VOUT=2.0V Outputs “a” through “g” VOUT=5.0V VCC=5.25V All outputs “ON” VOUT>1V VCC=5.25V ICCI Supply current All outputs blanked 50 70 mA NOTES: NE587 Programming: The NE587 output current can be programmed, provided a program resistor, RP, be connected between IP (Pin 8) and Ground (Pin 9). The voltage at IP (Pin 8) is constant (≈1.3V). Thus, a current through RP is IP ≈ 1.3V/RP, as shown in Figure 5. IO/IP is 20 in the 15 to 50mA output current range. 33 55 mA 20 250 µA 0.90 1.00 1.10 20 25 30 mA 3.5 4.5 V 0.2 0.5 V -0.7 mA -5 -200 µA 1.0 15 10 10 15 100 µA All inputs except BI BI TEST CONDITIONS LIMITS Min 4.75 2.0 2.0 Typ 5.00 Max 5.25 15 5.5 0.8 -1.5 V V µA UNIT V V August 31, 1994 532 Philips Semiconductors Linear Products Product specification LED decoder/driver NE587 AC ELECTRICAL CHARACTERISTICS VCC=5V, TA=25°C, RL=130Ω, CL=30pF including probe capacity. SYMBOL tDAV tDAV tW tS tH PARAMETER Propagation delay (Figure 2) Propagation delay (Figure 3) Latch enable pulse width (Figure 4) Latch enable setup time (Figure 4) Latch enable hold time (Figure 4) From data to LE From LE to data TEST CONDITIONS From data to output From LE to output 30 20 0 LIMITS Min Typ 135 135 Max UNIT ns ns ns ns ns NOTES: tDAV= (tHL+tLH) TRUTH TABLE BINARY INPUT 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 **BI INPUTS LE H L L L L L L L L L L L L L L L L L X RBI * L H X X X X X X X X X X X X X X X X D3 X L L L L L L L L L H H H H H H H H X D2 X L L L L L H H H H L L L L H H H H X D1 X L L L H H L L H H L L H H L L H H X D0 X L L H L H L H L H L H L H L H L H X H L H L L H L L L L L H L H H L H H H L L L L L H H L L L H H L H L H H H L L H L L L L L L L H H L H H H H a b c OUTPUTS d e H L H L H H H L H L H H L L L L H H f H L H H H L L L H L L H L L L L H H g H H H L L L L L H L L L L L H L H H RBO DISPLAY STABLE H L H L L H L L H L L H L H L H H H ** L H H H H H H H H H H H H H H H H L** STABLE BLANK 0 1 2 3 4 5 6 7 8 9 E H L P Blank Blank NOTES: H=HIGH voltage level, output is “OFF” L=LOW voltage level, output is “ON” X=Don’t care * The RBI will blank the display only if a binary zero is stored in the latches. ** RBO/BI used as an input overrides all other input conditions. NE587 PROGRAMMING 587 output current can be programmed by using a programming resistor, RP, connected between RP (Pin 8) and GND (Pin 9). The voltage at RP (Pin 8) is constant (K = 1.3V). A partial schematic of the voltage reference used in the NE587 is shown in Figure 1. Output current to program current ratio, IO/IP, is 20 in the 15mA to 50mA range. Note that IP must be derived from a resistor (RP), and not from a high-impedance source such as an IOUT DAC used to control display brightness. POWER DISSIPATION CONSIDERATIONS LED displays are power-hungry devices, and inevitably, somewhat inefficient in their use of the power supply necessary to drive them. Duty cycle control does afford one way of improving display efficiency, provided that the LEDs are not driven too far into saturation; but the improvement is marginal. Operation at higher peak currents has the added advantage of giving much better matching of light output, both from segment-to-segment and digit-to-digit. August 31, 1994 533 Philips Semiconductors Linear Products Product specification LED decoder/driver NE587 VCC IO 1:20 I P + V rP RP + 1.3V RP PIN 8 IP BAND GAP REFERENCE RP An output current of 10 to 50mA was chosen so that it would be suitable for multiplexed operation of large-size LED digits. When designing a display system, particular care must be taken to minimize power dissipation within the IC display driver. Since the output is a constant-current source, all the remaining supply voltage, which is not dropped across the LED (and the digit driver, if used), will appear across the output. Thus, the power dissipation will go up sharply if the display power supply voltage rises. Clearly, then, it is good design practice to keep the display supply voltage as low as possible, consistent with proper operation of the supply output current sources. Inserting a resistor or diode in series with the display supply is a good way of reducing the power dissipation within the integrated circuit segment driver, although, of course, total system power remains the same. Power dissipation may be calculated as follows. Referring to Figure 6, the two system power supplies are VCC and VS. In many cases, these will be the same voltage. Necessary parameters are: VCC VS ICC ISEG VF KDC Supply voltage to driver Supply voltage to display Quiescent supply current of driver LED segment current LED segment forward voltage at ISEG % Duty cycle Figure 1. TIMING DIAGRAMS D0–D3 tPLH OUTPUT tPHL LE = L VF, the forward LED drop, depends upon the type of LED material (hence the color) and the forward current. The actual forward voltage drops should be obtained from the LED display manufacturer’s literature for the peak segment current selected; however, approximate voltages at nominal rated currents are: Red Orange Yellow Green LE Figure 2. tP Data to Output LE tPLH tPHL 1.6 to 2.0V 2.0 to 2.5V 2.2 to 3.5V 2.5 to 3.5V tW D0–D3 D0–D3 OUTPUT OUTPUT Figure 3. tP Latch Enable to Output a f g b e d c Segment Identification August 31, 1994 534 ÉÉÉ ÉÉÉ ÉÉÉ ÉÉÉÉÉÉ ÉÉÉÉÉÉÉÉ ÉÉ ÉÉÉÉÉÉ ÉÉÉÉÉÉÉ ÉÉÉÉÉÉ ÉÉÉÉÉÉÉ ÉÉÉÉÉÉ ÉÉÉÉÉÉÉ tS tH Figure 4. Setup and Hold Times Philips Semiconductors Linear Products Product specification LED decoder/driver NE587 TYPICAL PERFORMANCE CURVES Supply Current vs Supply Voltage 40.0 RP = 1kΩ VOUT = 2V ALL OUTPUTS “ON” (0°C) (25°C) ICC 30.0 (mA) (70°C) 20.0 IOUT (mA) 10.0 Output Current vs Output Voltage RP = 1kΩ 40.0 (0°C) (25°C) 30.0 Normalized Output Current vs Temperature VCC = 5.0V 110.0 35.0 105.0 IOUT (%) 100.0 NE587 RP = 1kΩ (70°C) 25.0 95.0 20.0 4.0 90.0 4.4 4.8 5.2 5.6 6.0 6.4 0 1.0 2.0 VCC (VOLTS) 4.0 5.0 VOUT (VOLTS) 3.0 10 20 30 40 50 60 70 80 TEMP (°C) Normalized Output Current vs Supply Voltage VO = 2V, TA = 25°C 105 Maximum Power Dissipation vs Temperature Output Current vs Program Resistor 50.0 VCC = 5.0V VOUT = 2V TA = (25°C) 1000 40.0 102 IOUT (%) 100 NE587 RP = 1kΩ 800 PD (mW) 600 400 98 200 0 4.0 4.5 5.0 5.5 6.0 VCC (VOLTS) 0 25 TA (°C) VCC 0.01µF 50 75 10.0 30.0 IOUT (mA) 20.0 95 0.0 0 2.0 4.0 6.0 RP (kΩ) 8.0 10.0 These voltages are all for single-diode displays. Some early red displays had 2 series LEDs per segment; hence the forward voltage drop was around 3.5V. Thus, a maximum power dissipation calculation when all segments are on, is: P D + V CC x I CC ) x K DCmW (V S * V F) x 7 x I SEG D3 D2 D1 D0 VS a b c NE587 d e Assuming VS = VCC = 5.25V VF = 2.0V KDC = 100% PD MAX = 5.25 × 50 + 3.25 × 7 × 30mW = 945mW However, the average power dissipation will be considerably less than this. Assuming 5 segments are on (the average for all output code combinations), then PD MAX = 5.0 × 30 + 3.00 × 5 × 25mW = 525mW Operating temperature range limitations can be deduced from the power dissipation graph. (See Typical Performance Characteristics.) LE IP f g RBI RBO NOTE: Decoupling capacitor on VCC should be 0.01µF ceramic. Figure 5. Driving a Single Digit August 31, 1994 535 Philips Semiconductors Linear Products Product specification LED decoder/driver NE587 However, a major portion of this power dissipation (PD MAX) is because the current source output is operating with 3.25V across it. In practice, the outputs operate satisfactorily down to 0.5V, and so the extra voltage may be dropped external to the integrated circuit. Suppose the worst-case VCC/VS supply is 4.75 to 5.25V, and that the maximum VE for the LED display is 2.25V. Only 2.75V is required to keep the display active, and hence 2.0V may be dropped externally with a resistor from VCC to VS. The value of this resistor is calculated by: RS + 2.0 [ 7 x I SEG 1 10W ( W rating) 2 drops an appreciable voltage, rather than the saturating PNP transistors shown in Figure 9. For example a Darlington PNP or NPN emitter-follower may be preferable. Figure 8 shows the NE591 as the digit driver in a multiplexed display system. The NE591 output drops about 1.8V which means that the power dissipation is evenly distributed between the two integrated circuits. Where VS and VCC are two different supplies, the VS supply may be optimized for minimum system power dissipation and/or cost. Clearly, good regulation in the VS supply is totally unnecessary, and so this supply can be made much cheaper than the regulated 5V supply used in the rest of the system. In fact, a simple unsmoothed full-wave rectified sine wave works extremely well if a slight loss in brightness can be tolerated. A transformer voltage of about 3-4.5VRMS works well in most LED display systems. Waveforms are shown below: assuming worst case ISEG of 30mA. Hence now PD MAX = VCC × ICC + (VS - VV - RX × 7 × ISEG) × 7 × ISEG × KDC = 5.25 × 50 + 1.25 × 7 × 30mW = 525mW and PD av = 5.0 × 30 + 1.25 × 5 × 25 = 306 mW. If a diode (or 2) is used to reduce voltage to the display, then the voltage appearing across the display driver will be independent of the number of “ON” segments and will be equal to VS - VF - nVd, VD ≈ 0.8V Where n is the number of diodes used, power dissipation can be calculated in a similar manner. In a multiplexed display system, the voltage drop across the digit driver must also be considered in computing device power dissipation. It may even be an advantage to use a digit driver which VS ISEG The duty cycle for this system depends upon VS, VF and the output characteristics of the display driver. With VS = 4.9V peak VF = 2.0V The duty cycle is approximately 60%. August 31, 1994 536 Philips Semiconductors Linear Products Product specification LED decoder/driver NE587 VS VCC NE587 NE587 NE587 NE587 D3 D2 D1 D0 A0 A1 LE DIGIT DECODE BRIGHTNESS CONTROL Figure 6. 4-Digit Display with Brightness Control and Leading-Edge Ripple Blanking DATA BUS ADDRESS BUS ADDRESS DECODE NE591 D0 D1 D2 D3 D4 D5 D6 D7 VCC a .01µF b c d e f g NE587 RP Figure 7. Interfacing 8-Digit LED Display with µP Bus August 31, 1994 537 Philips Semiconductors Linear Products Product specification LED decoder/driver NE587 VS DIGIT 1 DIGIT 2 DIGIT 3 DIGIT 4 VCC D3 D2 D1 D0 LE RP NE587 Figure 8. Interfacing 4-Digit Multiplexed LED Display August 31, 1994 538