iC-NT LIGHT CHAIN PULSE DRIVER FEATURES APPLICATIONS ♦ Adjustable LED pulse operation, set range of 0.4..1A ♦ Controlled current slew rate enables short light pulses down to 1µs ♦ LED efficiency degradation compensated by positive current temperature coefficient ♦ Low standby current; circuit activation by input data ♦ Low power requirement for external set resistor ♦ Control logic with 3-step shift register ♦ Compatible to CMOS levels ♦ Data output buffer with built-in 120Ω wave impedance adaption ♦ Single 5V supply ♦ Thermal shutdown and power-down reset ♦ ESD protection ♦ Small outline package SO8 ♦ Suited for high-risk applications according to IEC 1496-1 ◊ Option: Extended temperature range of -20°C..85°C ♦ Electro-sensitive protective equipment (ESPE) ♦ Light curtain LED driver ♦ Light barrier LED driver PACKAGES SO8 BLOCK DIAGRAM +5V 2 iC-NT VDD CONTROL INPUTS 1 DOUT DIN 6µA 3 OUTPUT BUFFER LOGIC FF1 D CLK C R Q FF2 Q1 D C R Q 6 FF3 Q2 & D Q Q3 LED CURRENT SINK C R VDD +5V 4 500Ω 6µA S Dis SHEN LED 8 ISET 5 SEND 6µA 1 1 VDD PDR TR ENABLE A 1:1200 POWER DOWN RESET REFERENCE AND THERMAL SHUTDOWN VTREF + 50Ω RSET 1.8kΩ GND 7 ©1997 Rev A0 iC-Haus GmbH Integrierte Schaltkreise Am Kuemmerling 18, 55294 Bodenheim Tel (+49)6135-9292-0 Fax (+49)6135-9292-192 http://www.ichaus.com iC-NT LIGHT CHAIN PULSE DRIVER Rev A0, Page 2/8 DESCRIPTION The iC-NT device is an LED pulse driver for light barrier applications, especially light chain circuitries. The device, which is controlled by a shift register logic, features an adjustable LED current sink with a set range of 0.4..1A (at room temperature). For chain circuitries with several transmitters in operation, the internal set of three flipflops enables a secure beam and data shift control, free of race conditions. The decrease in LED efficiency with a rise in temperature is almost compensated by a positive temperature coefficient of the current sink. In order to generate steep light pulses, the LED switch off is actively supported by the discharge of its junction capacitance. The duration of this LED short-circuiting is controlled by a monoflop. In the event of a quick follow-up light pulse, a monoflop reset is performed automatically to protect against cross currents. The driver stage for the LED output prepares for a light pulse when DIN reads a high signal; synchronized with the CLK leading edge, the first flipflop transfers the DIN data to Q1 and powers up the LED sink. Since the chain is loaded with just one single high bit and DIN is given by the output DOUT of the previous device, input DIN now reads low at the falling edge of CLK. The LED current sink stops the power, at the same time as an internal data shift from Q1 to Q2 occurs. The LED pulse is well-defined by the time difference between two leading edges of the clock signal CLK. The second falling edge of CLK triggers the third flipflop and activates the next device in the chain via DOUT if enabled by SHEN. Since only one device is activated at a time, several iC-NT drivers may share one resistor, RSET, to define the LED current value. The shift register is reset and the LED current sink is turned off in the event of excessive temperature or undervoltage. Protective diodes to prevent destruction through ESD are also included. The iC-NT device fulfills safety requirements according to IEC 1496-1. An extended temperature range of -20°C..85°C is also available as an option. PACKAGE SO8 to JEDEC Standard PIN CONFIGURATION SO8 (top view) PIN FUNCTIONS No. Name Function 1 2 3 4 5 6 7 8 DIN VDD CLK SHEN ISET DOUT GND LED Data Input Supply Voltage 5V Clock Shift Enable Current Adjust, attachement RSET Data Output Ground Pulse Output, LED Cathode iC-NT LIGHT CHAIN PULSE DRIVER Rev A0, Page 3/8 ABSOLUTE MAXIMUM RATINGS Values beyond which damage may occur; device operation is not guaranteed. Item Symbol Parameter Conditions Fig. Unit Min. Max. G001 VDD Supply Voltage -0.5 7 V G002 V() Voltage at Inputs DIN, CLK, SHEN -0.5 VDD+0.5 V G003 V() Voltage at DOUT, ISET, LED -0.5 VDD+0.5 V E001 Vd() ESD Susceptibility at VDD, ISET and digital inputs/outputs MIL-STD-883, HBM 100pF discharged through 1.5kΩ 2 kV E002 Vd(LED) ESD Susceptibility at LED with standard circuitry, HBM 100pF discharged through 1.5kΩ 2 kV TG1 Tj Junction Temperature -40 150 °C TG2 Ts Storage Temperature -40 150 °C 5 THERMAL DATA Operating Conditions: VDD= 4.75..5.5V Item Symbol Parameter T1 Ta Operating Ambient Temperature Range (Extended temperature range of -20..85°C on request) T2 Rthja Thermal Resistance Junction to Ambient Conditions Fig. Unit Min. 0 surface mounted without special cooling areas All voltages are referenced to ground unless otherwise noted. All currents into the device pins are positive; all currents out of the device pins are negative. Typ. Max. 70 °C 170 K/W iC-NT LIGHT CHAIN PULSE DRIVER Rev A0, Page 4/8 ELECTRICAL CHARACTERISTICS Operating Conditions: VDD= 4.75..5.5V, RSET= 1.8..4.5kΩ, Tj= -20..125°C, unless otherwise noted Item Symbol Parameter Conditions Tj Fig. °C Unit Min. Typ. Max. Total Device 001 VDD Permissible Supply Voltage Range 002 I(VDD) Supply Current in VDD (Standby) 003 I(VDD) 4.75 5.5 V Analog section disabled; DIN= lo, CLK,SHEN= hi or lo, logic levels: lo= 0..0.45V, hi= VDD-0.45V..VDD 60 µA Supply Current in VDD Analog section disabled; DIN= lo CLK, SHEN hi or lo, logic levels: lo= 22%VDD, hi= 78%VDD 1 mA 004 I(VDD) Supply Current in VDD Analog section enabled; RSET≥ 1.8kΩ, LED current sink off -20 27 85 Toff 7.5 7.5 8.5 1.0 mA mA mA mA 005 I(VDD) Supply Current in VDD Analog section enabled; RSET≥ 1.8kΩ, LED current sink on -20 27 85 Toff 25 25 26 1.0 mA mA mA mA 006 VDDon Turn-on Threshold VDD (Power-on Release) 4.3 V 007 VDDoff Undervoltage Threshold at VDD (Power-down Reset) decreasing voltage VDD 2.7 008 VDDhys Hysteresis VDDhys= VDDon-VDDoff 100 009 Vc()hi Clamp Voltage hi at DIN, CLK, SHEN, DOUT, ISET, LED Vc()hi= V()-VDD, I()= 10mA 0.4 1.25 V 010 Vc()lo Clamp Voltage lo at DIN, CLK, SHEN, DOUT, ISET, LED I()= -10mA, VDD= 0V other pins open -1.25 -0.4 V 011 Toff Shutdown Temperature 110 150 °C V mV LED Current Sink 101 V(ISET) Reference Voltage at ISET -20 27 85 Toff 102 TC(ISET) Temperature Coefficient of Reference Voltage at ISET 1.27 1.50 1.79 0 27 0.30 0.33 V V V V 0.36 %/K 103 CR() Current Ratio I(LED) / -I(ISET) 104 I(LED) LED Pulse Current duty cycle I(LED)≤ 1%, RSET= 1.8kΩ, V(LED)= 1.0V..VDD -20 27 85 Toff 0.65 0.82 0.93 0.85 1.00 1.2 0 1.06 1.18 1.48 A A A A 105 I(LED) LED Pulse Current duty cycle I(LED)≤ 1%, RSET= 4.5kΩ, V(LED)= 0.85V..VDD -20 27 85 Toff 0.26 0.33 0.37 0.34 0.40 0.48 0 0.44 0.48 0.61 A A A A 106 tr(LED) LED Current Rise Time 3 150 ns 107 tf(LED) LED Current Fall Time 3 150 ns 400 ns 108 tdis(LED) LED Discharge Duration 1200 LED shutdown, switch Sdis closed iC-NT LIGHT CHAIN PULSE DRIVER Rev A0, Page 5/8 ELECTRICAL CHARACTERISTICS Operating Conditions: VDD= 4.75..5.5V, RSET= 1.8..4.5kΩ, Tj= -20..125°C, unless otherwise noted Item Symbol Parameter Conditions Tj Fig. °C Unit Min. Typ. Max. LED Current Sink (continued) 109 Ir(LED) LED Discharge Current V(VDD/LED)= 1.5V 200 110 Rpu(LED) Pull-up Resistor at LED 300 500 mA 850 Ω 78 %VDD Control Inputs DIN, SHEN, CLK 201 Vt()hi Threshold Voltage hi 202 Vt()lo Threshold Voltage lo 22 %VDD 203 Vhys() Schmitt-Trigger Input Hysteresis 400 mV 204 Ipd() Pull-Down Current V()= 5.0V 3 6 12 µA Output Buffer DOUT 301 Vs()hi Saturation Voltage hi Vs(DOUT)hi= VDD-V(DOUT), I(DOUT)= -4mA 0.4 V 302 Vs()lo Saturation Voltage lo I(DOUT)= 4mA 0.4 V 303 Isc()hi Short-Circuit Current hi V(DOUT)= 0V -40 -20 mA 304 Isc()lo Short-Circuit Current lo V(DOUT)= VDD 20 40 100 mA 305 Rout() Output Resistance VDD= 5.0V, V(DOUT)= 2.5V 80 120 190 Ω 306 tr() Rise Time CL(DOUT)≤ 50pF 20 60 ns 307 tf() Fall Time CL(DOUT)≤ 50pF 20 60 ns -100 Switching Characteristics 401 tphl(CLK LED Pulse Turn-on Delay -LED) DIN= hi, CLK lo→hi until I(LED)= 10% set value 4 100 ns 402 tplh(CLK LED Pulse Turn-off Delay -LED) DIN= lo, CLK lo→hi until I(LED)= 90% set value 4 80 ns 403 tplh(CLK- DOUT Switch Delay hi DOUT) CL(DOUT)≤ 50pF, CLK hi→lo 2 25 60 ns 404 tphl(CLK- DOUT Switch Delay lo DOUT) CL(DOUT)≤ 50pF, CLK hi→lo 2 25 60 ns iC-NT LIGHT CHAIN PULSE DRIVER Rev A0, Page 6/8 OPERATING REQUIREMENTS: Logic Operating Conditions: VDD= 4.75..5.5V, Ta= 0..70°C, CL()= 50pF, input levels lo= 0..0.45V, hi= VDD-0.45V..VDD, see Fig. 1 for reference levels and waveforms Item Symbol Parameter Conditions Fig. Unit Min. Max. I1 ten Activation Time (standby to operation): DIN lo→hi before CLK lo→hi 4 5 µs I2 tset1 Setup time: DIN stable before CLK lo→hi 2 50 ns I3 thold1 Hold time: DIN stable after CLK lo→hi 2 50 ns I4 tset2 Setup time: SHEN stable before CLK hi→lo 2 50 ns I5 thold2 Hold time: SHEN stable after CLK hi→lo 2 50 ns I6 tw LED Pulse time: 1st to 2nd CLK lo→hi 4 1.0 µs Fig. 1: Reference levels Fig. 2: Timing characteristics Fig. 3: LED Current Pulse Fig. 4: Chain configuration (SHEN= hi), LED pulse definition by clock signal iC-NT LIGHT CHAIN PULSE DRIVER Rev A0, Page 7/8 APPLICATIONS INFORMATION Light curtain The circuit in Figure 5 shows iC-NT chained to a light curtain where consecutive LEDs emit clock-driven light pulses. When discussing the function of iC-NT, it is assumed that all flipflops in IC1..ICn have been reset, for example after the operating voltage has been switched on. The signal DIN1= hi activates the IC1 current sink which is switched to LED1 with the CLK rising edge. With DIN1= lo, the next CLK rising edge resets FF1, turns off the LED and deactivates the current sink in IC1. Simultaneously, FF1 sends the stored information to FF2. FF3 also accepts this information via the CLK trailing edge (provided that SHEN= hi) and activates the current sink in the next component, IC2, via the output driver. The pulse diagram in Figure 6 is also valid for the subsequent components in the chain, i.e. the ICs switched as a light curtain make up a clock-driven shift register which passes on the input information. The typical timing of a CLK signal, shown in Figure 6, is characterized by two successive pulses which determine the length of a light pulse tw from 1..3µs, followed by a longer activation time of ten ≥5µs. In general, the CLK pulse interval is determined and lengthened by the activation time required by the receiver or by more extensive, system-set default options. Because of the high LED pulse currents, the PCB layout of the light curtain sender must be designed to avoid large voltage drops on the supply lines. The high, short-term pulse current is provided by back-up capacitors C1..Cn at the pulse driver ICs; these should have a low inductance due to the high current increase rate. The leads to the LED anode and to iC-NT’s GND pin should be as short as possible. The capacitors selected should ensure that the voltage drop caused by the light pulse is less than 1V, i.e. that C1..Cn= 1µF for a light pulse of 1A x 1µs, for example. In practice, the voltage at the IC drops much less during a light pulse, as charge from the back-up capacitors of neighboring ICs also flows into the chip. A low-inductance capacitance distribution can be achieved more economically by placing further smaller capacitors in parallel. Since only one device is activated at a time within one section of a light curtain, several iC-NTs may share the external resistor RSET, needed to set the pulse current. This parallel chain circuit should be limited to ca. 5 ICs due to the increasing capacitive loading at pin ISET. Fig. 5: Schematic of a Chain Configuration iC-NT LIGHT CHAIN PULSE DRIVER Rev A0, Page 8/8 Fig. 6: Signals of the Chain Configuration of Figure 5 ORDERING INFORMATION Type Package Order designation iC-NT SO8 iC-NT-SO8 For information about prices, terms of delivery, options for other case types, etc., please contact: iC-Haus GmbH Am Kuemmerling 18 D-55294 Bodenheim GERMANY Tel (+49)6135-9292-0 Fax (+49)6135-9292-192 http://www.ichaus.com This specification is for a newly developed product. iC-Haus therefore reserves the right to modify data without further notice. Please contact us to ascertain the current data. The data specified is intended solely for the purpose of product description and is not to be deemed guaranteed in a legal sense. Any claims for damage against us - regardless of the legal basis - are excluded unless we are guilty of premeditation or gross negligence. We do not assume any guarantee that the specified circuits or procedures are free of copyrights of third parties. Copying - even as an excerpt - is only permitted with the approval of the publisher and precise reference to source.