U2481B/ U2482B TELEFUNKEN Semiconductors Automotive Lamp Outage Monitor Description The U2481B and the U2482B multicomparator circuits are designed to monitor automotive illumination by sensing the voltage drop across shunt resistors. Provided with extremely low comparator thresholds, these ICs can be used together as a chip set to build an entire lamp monitor system. Single operation of both circuits is also possible. As a special feature for brake lamp monitoring, the U2481B contains a latch stage connected to one of its triple comparators. With – 4 single comparators – 1 double comparator and – 2 triple comparators each of the integrated circuits monitors up to 12 lamps and up to 6 fuses. All comparator stages are combined together to control the common output stage. Features Benefits Extremely low comparator thresholds of typically 3.5 mV Extremely low threshold voltage gives low voltage drop via shunt resistor. Power dissipation of the lamp monitor module is minimized Internal compensation for copper shunts Internal compensation for voltage-dependent bulb characteristic Perfect EMC in conjunction with an appropriate pc board layout Comparator input voltage may exceed supply voltage Internal protection measures for pulses according to ISO TR 7637/1 ESD according to MIL-SID-883 C test method 3015.7 – Human body model: 4 kV – Machine model: 200 V EMI protection (TEM cell up to 100 V/m) Applications Both ICs can be used in any kind of vehicle with a 12 V supply. It is sufficient to insert small resistors into the lamp wiring and to provide the dashboard instrument Rev. A1: 21.08.1995 cluster with a pilot lamp. These ICs increase the safety and add comfort features. Preliminary Information 1 (11) U2481B/ U2482B TELEFUNKEN Semiconductors Block Diagram VB 20 REFK1 IN1K1 28 Ref K1 VS 13 mV E1 27 19 VB Voltage drift of comparator threshold IT = f (VB) + – IT IT VS Power on Reset Stabilized voltage Vstab = 5.2 V POR IT Divider REFK2 IN1K2 1 Ref K2 13 mV 2 IN1K3 IN2K3 IN3K3 INFK3 REFK4 IN1K4 INFK5 REFK5 IN1K5 IN2K5 7 REFK7 IN1K7 IN2K7 IN3K7 Cl2 Ref K3 3.5 mV 6 E1 8 9 Up down counter T = 1.2 s Cl2 E2 Start High at forward counter end E3 26 VS Set Out High at Start return counter zero Reset Cl1 24 Ref K4 3.5 mV 25 14 E1 OUT 16 4 Ref K5 3.5 mV 3 Out E1 5 E2 10 12 13 17 POR INFK6 Set Ref K7 3.5 mV 3.5 mV Cl2 E1 IN1K6 * Connection to GND only for U2482B (latch disabled High at Start forward counter end Start High at return counter zero E2 REFK6 21 VS Up down counter T = 1.2 s E1 E3 22 K6 Ref + – 23 11 Reset Latch for stoplamps VB INF OSC E1 Cl1 REFK3 15 Oscillator Clock 1 Clock 2 2-TOsc 20-TOsc 18 GND * Cl1 94 8833 Figure 1. 2 (11) Preliminary Information Rev. A1: 21.08.1995 U2481B/ U2482B TELEFUNKEN Semiconductors Pin Description REFK2 1 28 REFK1 IN1K2 2 27 IN1K1 In1K5 3 26 INFK3 REFK5 4 25 IN1K4 IN2K5 5 24 REFK4 IN1K3 6 23 Pin 1 Symbol REFK2 2 3 4 IN1K2 IN1K5 REFK5 5 6 7 IN2K5 IN1K3 REFK3 8 9 10 IN2K3 IN3K3 IN1K7 11 REFK7 12 IN2K7 INF REFK3 7 22 REFK6 13 IN3K7 IN2K3 8 21 IN1K6 14 15 16 OUT OSC INFK5 IN3K3 9 20 VB 17 INFK6 IN1K7 10 19 VS 18 19 20 GND VS VB REFK7 11 18 GND 21 22 IN1K6 REFK6 IN2K7 12 17 INFK6 23 24 INF REFK4 IN3K7 13 16 INFK5 25 26 IN1K4 INFK3 14 15 OSC 27 28 IN1K1 REFK1 OUT 94 8831 Function Reference for threshold voltage single comparator K2 Input 1; single comparator K2 Input 1; double comparator K5 Reference for threshold voltage; double comparator K5 Input 2; double comparator K5 Input 1; triple comparator K3 Reference for threshold voltage; triple comparator K3 Input 2; triple comparator K3 Input 3; triple comparator K3 Input 1; triple comparator K7 (U2481B with latch) Reference for threshold voltage; triple comparator K7 (U2481B with latch) Input 2; triple comparator K7 (U2481B with latch) Input 3; triple comparator K7 (U2481B with latch) Output for pilot lamp R/C combination for oscillator Fuse monitor input ; double comparator K5 Fuse monitor input; single comparator K6 Ground Supply voltage Reference voltage of comparators Input1; single comparator K6 Reference for threshold voltage; single comparator K6 Input; brake fuse comparator Reference for threshold voltage; single comparator K4 Input 1; single comparator K4 Fuse monitor input; triple comparator K3 Input 1; single comparator K1 Reference for threshold voltage; single comparator K1 Figure 2. Pin configuration Rev. A1: 21.08.1995 Preliminary Information 3 (11) U2481B/ U2482B TELEFUNKEN Semiconductors 150 R1 1000 VBatt R2 C2 0.1 F C1 15 F VB 20 VS Rosc 19 82 k 28 A 1 k Fuse 15 Osc Cosc 27 10 nF 2 k Pilot lamp 1.2 W U2481B U2482B 2 k 16 4 14 1 k Shunt Out Kl 61 3 B 2 k Shunt 5 2 k 95 10689 Out A: Example of a “single comparator” using the fuse as a shunt resistor B: Example of a “double comparator” using copper shunts and additional fuse monitoring Figure 3. Basic application diagram 4 (11) Preliminary Information Rev. A1: 21.08.1995 TELEFUNKEN Semiconductors U2481B/ U2482B Functional Description Power Supply, Pins 19 and 20 The Ics have two supply pins. The IC itself is supplied via Pin 19 (stabilized voltage, POR-circuitry). Pin 20 supplies only the current sources of the comparators. Both pins have an an internal 21 V Zener Diode for protection. For reasons of interference protection and surge immunity the supply voltage pins have to be provided with RC-circuitries as shown in figure... The resistors limit the current in the case of overvoltage, whereas the capacitors smooth the supply voltage. Recommended values: Pin 19: R = 150 ; K = 0.1 F Pin 20: R = 1000 ; K = 0.1 F An external diode protects the IC against battery reversal. Power-On-Reset When the supply voltage is switched on, a power-on-reset pulse is generated internally which resets the brake lamp monitor latch and the counter stages. Oscillator, Pin 15 The RC-oscillator is the time base for clock 1 and clock 2 (see block diagram) which are desired from a divider stage and fed to the two upward and downward counters. The oscillator frequency fosc is mainly determined by the external R/C components and an integrated resistor. The capacitor K is charged by the external resistor and discharged by the integrated one. Because of the temperature characteristic and the tolerances of the integrated 2 k-resistor, the external one has to have considerable higher value in order to achieve a stable frequency. Calculation of the frequency: f osc 1 c1 (0.74 R osc 2260 ) osc f osc With the recommended values In order to disable monitoring when the lamps are switched off, therefore the comparator outputs are disabled if the reference voltage Vref < VMin with VMin = 0.33VB. As protection against transients on the supply, all comparator inputs require external resistors. Their tolerances directly influence the comparator threshold accuracy. Resistors with a 1% tolerance are recommended. Single comparators: The inputs (K1, K2, K4, K6) sink currents of typically 10 A each. During switch-over, the currents of reference and input pins are identical. Therefore identical external protection resistors (R = 1 k) are required. Double comparator: The reference input (K5) sinks a current of typically 20 A; its inputs sink currents of typically 10 A each during switch-over. Therefore the external protection resistors must provide R = 1 k for REFK5 and R = 2 k each for IN1K5 and IN2K5. Triple comparators: The reference inputs (K3 and K7) sink currents of typically 30 A. All inputs (IN1K3, IN2K3 IN3K3, and IN1K7, IN2K7, IN3K7) sink the identical typical current of 10 A during switch-over. Therefore the external protection resistor must provide R = 1 k for REFK3 and REFK7 and R = 3 k at each input. Fuse Monitoring The internal EXOR conjunction of comparators K1 and K2 allows fuse monitoring for both lamps. Even a simultaneous blowout of both fuses is detected. The pins INFK3, INFK5 and INFK6 with their EXOR gates can be used for additional fuse monitoring. Rosc = 82 k and Cosc = 10 nF Detection threshold for a blown fuse is Vref < VMin with VMin = 0.33 VB (VB = reference voltage of comparators). fosc ≈ 1.58 kHz Comparators Comparators K1 and K2: threshold voltage of typically Vth = 13 mV; designed to monitor high- and low-beam bulbs, where the fuses can be used as shunt resistors. Comparators K3 to K7: threshold voltage of typically Vth = 3.5 mV; designed for all other monitor purposes. Due to the integrated compensation circuitry, these comparators are suitable for pc layer copper shunts. Rev. A1: 21.08.1995 A bulb is detected as “good” as long as the voltage drop via the shunt resistor exceeds the threshold voltage. The pilot lamp is off. A failed bulb is detected if the voltage drop via the shunt resistor is smaller than the threshold voltage. The pilot lamp is on. An external transistor is necessary to drive the pilot lamp. Pin INF is used for brake fuse monitoring. With a voltage drop VF > 4.8 V across the fuse, the comparator detects a blown fuse. A voltage drop VF < 2.8 V represents a “good” fuse. U2481B’s comparator K7 is connected to a latch, thus a brake lamp outage is memorized. Preliminary Information 5 (11) U2481B/ U2482B Integrated Delay, Debouncing, Failure Display As soon as a comparator detects a failure a slow upward counter is started in order to generate the delay time, tdel = 1.2 s. With a consistent failure the output stage is enabled after tdel. If the failure disappears during tdel a fast downward counter is started in order to generate the reset time treset 135 ms. The upward counter is reset, the output stage stays disabled. Benefits: Intermittent contacts in the wire harness do not activate the pilot lamp! Even cyclical intermittent contacts are screened out as long as the pulse/pause ratio is smaller than 10:1. In the case of higher duty cycles the upward counter may reach its trigger threshold for the output activation after t > tdel. Individual delay- and reset times can be adjusted with external R/C components according to (see “oscillator”) – tdel = 1930 x tosc – treset = 198 x tosc 6 (11) TELEFUNKEN Semiconductors Latch for Brake Lamp Monitor A failure of a brake lamp detected by comparator K7 or a blown fuse in the brake circuitry is memorized after the delay time has expired. A reset of the latch can only be performed with a “poweron-reset”. Output Stage The output is a Darlington stage stage with protection diodes to VS and IC ground. The output is designed to drive an external pilot lamp with an external PNP transistor. At the end of the delay time the output stage is switched on and can source a current of Iout = –10 mA with a typical saturation voltage of Vsat = 1 V. Test Mode With VTEST = 23 V (20 mA) applied to Pin osc, via a 200 resistor the delay time stage can be bypassed for test purposes. A failure detection will be displayed immediately to save time during threshold testing. Preliminary Information Rev. A1: 21.08.1995 U2481B/ U2482B TELEFUNKEN Semiconductors Application Hints Layout Recommendations for Copper Layer Shunts Lamp outage monitor systems can be produced most costefficiently if stamped shunt resistors are replaced by copper layer shunts which are generated with the pc board layout. The U2481B and the U2482B are suitable for this application because of their comparator thresholds, which are compensated in reference to the temperature characteristic of copper. A constant lamp current, ILAMP = VTh/Rsh with threshold voltage VTh = f(T) and shunt resistor Rsh = f(T), is achieved if the comparator threshold and the shunt resistor have identical temperature characteristics. With the temperature coefficient of copper acu = 3.9<10–3 1/K, a copper shunt changes its nominal value by 52% if the automotive ambient temperature range of tamb = –40 to +95°C is taken into consideration. Two equations for calculation of the shunt resistance: Rshunt = RA<L/Wcn (with RA = Cu sheet resistance) Rshunt = VTh / 1/2 ILAMP Thus the length of copper shunt is calculated as: L = 2<VTh<Wcn / RA<ILAMP L = 215 mm For a reasonable pc-layout a meander-shaped shunt resistor is recommended. The high lamp currents may cause hot spots at sharp edges of the copper shunts. That may deteriorate accuracy of the measurement. Therefore it is recommended to layout the copper shunts with smoothed curves. In accordance to figure...the meander may be formed by 4 straight tracks (length LS each) and 3 connecting 180° ares (length L are each). If the mean are radius is selected to r = Wcn the are lenght becomes Lare = p Wcn. Thus the total lenght is Examples for sheet resistances of copper shunts (Tamb = 25°C): RA = 0.5 mW/square (35.1 mm layer thickness) RA = 0.25 mW/square (70 mm layer thickness) L = 4 LS + 3 Lare How to Lay Out Copper Shunts (figure 3) L S + 1 (L * 3 4 The width of the copper trace has to be selected in reference to a low current-effected temperature increase. The copper trace must be capable of peak currents which do not blow the fuse. The peak currents are specified by the car manufacturers. Example: A 7.5 A fuse allows a peak current of 26 A (1 s), 15 A (10 s) or 10 A (60 s). The copper shunt length has to be calculated between the two sense connections to the comparator. The connection of the common reference input of double and triple comparators has to be considered carefully. = 4 LS + 3 p Wcn With L = 215 mm the track length becomes p W cn) LS = 47.8 mm Using Fuses as Shunt Resistors This cost saving method can be used if the following assumptions are fulfilled: – – – Each lamp needs a dedicated fuse The fuse socket is mounted within the monitor module to connect the sense linesare suitable for this monitor task because of their comparator thresholds are compensated for the fuse temperature coefficient of aF = 4.1<10–3 1/K Calculation example for a copper shunt used with a 4 W bulb. Calculation Example for a 55 W Bulb and a ILAMP = 0.325 A Failure criterion: I = 1/2<ILAMP 10 A fuse is capable of I = 13.5 A Copper layer thickness: 70 mm Comparator threshold voltage (U2481B, U2482B): VTh = 3.5 mV Measured voltage drop across the fuse: VF = 52 mV Measured current: ILAMP = 4.2 A Calculated resistance: RF = 12.4 mW Selected comparatore threshold: VTh = 1/4 VF = 13 mV (typically); With a lamp current ILAMP < VTh/RF =< 1.05 A the comparator detects a blown fuse. Assumed copper width for temperature increase DTcu < 50°C: Wcu = 2.5 mm (13.5 A, 70 mm) Rev. A1: 21.08.1995 7.5 A fuse: Preliminary Information 7 (11) U2481B/ U2482B TELEFUNKEN Semiconductors Wcn = 2.5 mm to lamp to lamp switch LS Larc Wcn R2 28 27 R1 26 25 24 23 22 21 20 19 18 17 16 15 9 10 11 12 13 14 1 2 3 4 5 6 7 8 94 8832 U2481B U2482B Figure 4. Design example for a copper shunt with meander shape Absolute Maximum Ratings Parameters Supply voltage Pulse current (2 ms) Short circuit current (reversed battery) Output current Junction temperature Symbol VS, VBatt IS ISC Iout Tj Value 16.5 1.1 170 –12 150 Unit V A mA mA °C Symbol RthJA Tamb Tstg Value 110 –40 to +100 –55 to +125 Unit K/W °C °C Thermal Resistance Parameters Thermal resistance Ambient temperature range Storage temperature range 8 (11) SO 28 Preliminary Information Rev. A1: 21.08.1995 U2481B/ U2482B TELEFUNKEN Semiconductors Electrical Characteristics Tamb = –40 to +100_C, VBatt (Kl. 15) = 10 to 15 V, supply series resistors and input protection rsistors connected (see figure 1 “block diagram” and figure 2 “basic application schematic”) unless otherwise specified. Parameters Supply Operating voltage Supply current Power on reset (POR) Comparators Comparator input current during switch over Comparator thresholds VT1 of comparators K1 and K2 (VT1 = VRef... – VIN...) Voltage characteristic Temperature characteristic Comparator thresholds VT2 of comparators K3 to K7 (VT2 = VRef... – VIN...) Test Conditions / Pins Rev. A1: 21.08.1995 Min. VBatt 9 VBatt = 13 V, V14 = low Pin 20 Pin 19 Tamb = 25°C Pin 19 VBatt (Kl. 15) VBatt = 13 V Pins 27, 28 Pins 1, 2 Pins 24, 25 Pins 21, 22 Pin 7 Pins 6, 8, 9 Pin 11 Pins 10–12 Pin 4 Pins 3,5 VS = 10 V Pins 1, 2, 27, 28 VS = 13 V VS = 15 V 0.3 3 3.0 3.7 I27, I28 I 1 , I2 I24, I25 I21, I22 I7 I 6 , I8 , I9 I11 I10,I11,I12 I4 I 3 , I5 VT1x x = Pin No. 8.5 10.0 11.0 DVT1 DTT1 Typ. 0.7 5 10 10 10 10 30 10 30 10 20 10 11.5 13.0 14.0 0.5 3900 Max. Unit 16 V 1.1 7 4.2 5.0 mA mA V V mA 14.5 16.0 17.0 mV mV/V ppm/°K Pins 6, 7, 8, 9 Pins 24, 25 Pins 3, 4, 5 Pins 21, 22 Pins 10, 11, 12 VS = 10 V VS = 13 V VS = 15 V Voltage characteristic Temperature characteristic Min. comparator input voltage for detection Output Output current Output saturation voltage Symbol VT1x x = Pin No. DVT2 DTT2 VMin all Ref-pins VBatt = 13 V Iout = –10 mA Pin 19–Pin 14 1.5 2.0 2.3 Pin 14 I14 VSat Preliminary Information 3.0 3.5 3.8 0.17 3900 0.33 VBatt –10.0 1.0 4.5 5.0 5.3 mV mV/V ppm/°K 1.5 mA V 9 (11) U2481B/ U2482B Parameters Protection Voltage of Zener diodes Oscillator Oscillator frequency Delay time Debounce time Break fuse Brake fuse detection threshold Input current Trigger threshold (internal pull down resistor) Input current Test Test voltage for delay time override TELEFUNKEN Semiconductors Test Conditions / Pins Pin 19 Pin 20 all Ref... and IN... pins Rosc = 82 k, Cosc = 10 nF, Rosc = 82 k, Cosc = 10 nF Rosc = 82 k, Cosc = 10 nF Min. VS VB 21 19 VRef..., VIN... 19 fosc 1.58 Max. Unit V kHz Pin 15 1.1 1.2 1.3 s tdb 115 125 135 ms Pin 23 VTB 2.8 3.8 4.8 V Pin 23 Pins 16, 17, 28 I23 VTTx A V I 100 0.33 VBatt 100 V15 23 V x=16,17,18 VBatt = 13 V I = 20 mA Typ. td VBatt V23 = 13 V Symbol Pin 15 A Dimensions in mm Package: SO 28 95 9932 10 (11) Preliminary Information Rev. A1: 21.08.1995 TELEFUNKEN Semiconductors U2481B/ U2482B Ozone Depleting Substances Policy Statement It is the policy of TEMIC TELEFUNKEN microelectronic GmbH to 1. Meet all present and future national and international statutory requirements. 2. Regularly and continuously improve the performance of our products, processes, distribution and operating systems with respect to their impact on the health and safety of our employees and the public, as well as their impact on the environment. It is particular concern to control or eliminate releases of those substances into the atmosphere which are known as ozone depleting substances ( ODSs). The Montreal Protocol ( 1987) and its London Amendments ( 1990) intend to severely restrict the use of ODSs and forbid their use within the next ten years. Various national and international initiatives are pressing for an earlier ban on these substances. TEMIC TELEFUNKEN microelectronic GmbH semiconductor division has been able to use its policy of continuous improvements to eliminate the use of ODSs listed in the following documents. 1. Annex A, B and list of transitional substances of the Montreal Protocol and the London Amendments respectively 2 . Class I and II ozone depleting substances in the Clean Air Act Amendments of 1990 by the Environmental Protection Agency ( EPA) in the USA 3. Council Decision 88/540/EEC and 91/690/EEC Annex A, B and C ( transitional substances ) respectively. TEMIC can certify that our semiconductors are not manufactured with ozone depleting substances and do not contain such substances. We reserve the right to make changes to improve technical design and may do so without further notice. Parameters can vary in different applications. All operating parameters must be validated for each customer application by the customer. Should the buyer use TEMIC products for any unintended or unauthorized application, the buyer shall indemnify TEMIC against all claims, costs, damages, and expenses, arising out of, directly or indirectly, any claim of personal damage, injury or death associated with such unintended or unauthorized use. TEMIC TELEFUNKEN microelectronic GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany Telephone: 49 ( 0 ) 7131 67 2831, Fax number: 49 ( 0 ) 7131 67 2423 Rev. A1: 21.08.1995 Preliminary Information 11 (11)