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U643 Dataheets PDF



Part Number U643
Manufacturers ATMEL Corporation
Logo ATMEL Corporation
Description Flasher/ 30-mohm Shunt
Datasheet U643 DatasheetU643 Datasheet (PDF)

U643B Flasher, 30-mW Shunt Description The bipolar integrated circuit U643B is used in relaycontrolled automotive flashers where a high-level EMC is required. Lamp outage is indicated by frequency doubling during hazard warning as well as direction mode. Features D Temperature and supply voltage compensated flashing frequency D Frequency doubling indicates lamp outage D Relay driver output with high current carrying capacity and low saturation voltage D Minimum lamp load for flasher operation: .

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U643B Flasher, 30-mW Shunt Description The bipolar integrated circuit U643B is used in relaycontrolled automotive flashers where a high-level EMC is required. Lamp outage is indicated by frequency doubling during hazard warning as well as direction mode. Features D Temperature and supply voltage compensated flashing frequency D Frequency doubling indicates lamp outage D Relay driver output with high current carrying capacity and low saturation voltage D Minimum lamp load for flasher operation: ≥ 1 W D Very low susceptibility to EMI D Protection according to ISO/TR 7637/1 level 4 Block Diagram + VS + 49 6 C1 4 Measuring comparator K 1 V6–81 mV 20 kW K1 2 R3 Shunt 5 kW 7 30 mW K2 R1 Pulse generator 3 49 a–Comparator K2 20 kW 49 a–Comparator K3 K3 23 V 20 kW 5 kW IC Ground 1 95 9756 Relay 8 R2 49 a 1.5...2.2 kW 5 R4 470 W 5 W 21 W 21 W 21 W 21 W 5 W Indicator lamps GND – 31 Figure 1. Application circuit as a car flasher, Resistor R1 and R2: 1/4 Watt R4 for protection against continuous reversed polarity: 0.5 Watt Ordering Information Extended Type Number U643B U643B-FP Package DIP8 SO8 Remarks Rev. A3, 10-Apr-01 1 (5) U643B Pin Description Pin 1 2 3 4 5 6 7 8 Symbol GND VS REL OSC OSC VS LD SI IC ground Supply voltage VS Relay driver C1 Oscillator R1 Oscillator Supply voltage VS Lamp failure detection Start input (49a) Figure 2. Pinning OSC REL 3 4 VS 2 7 LD Function GND 1 8 SI U643B 6 Vs 5 OSC 94 9290 Functional Description Pin 1, GND The integrated circuit is protected against damage via resistor R4 to ground (–31) in the case of battery reversal. An integrated protection circuit together with external resistances R2 and R4 limits the current pulses in the IC. Pin 2, Supply voltage, VS - Power The arrangement of the supply connections to Pin 2 must be so as to ensure that, on the connection printed circuit board (PCB), the resistance of VS to Pin 6 is lower than that to Pin 2. Pin 3, Relay control output (driver) The relay control output is a high-side driver with a low saturation voltage and capable to drive a typical automotive relay with a minimum coil resistance of 60 W. Pin 4 and 5 Oscillator Flashing frequency, f1, is determined by the R1C1 components as follows (see figure 1): f1 [ where 1 C1 Hz mized layer resistance from point VS / shunt to Pin 6 is recommended. Pin 7, Lamp outage detection The lamp current is monitored via an external shunt resistor R3 and an internal comparator K1 with its reference voltage of typ. 81 mV (VS = 12 V). The outage of one lamp out of two lamps is detected according to the following calculation: Nominal current of 1 lamp: 21 W / (VS = 12 V): Ilamp = 1.75 A Nominal current of 2 lamps: 2 x 21 W / (VS = 12 V): Ilamp = 3.5 A. The detection threshold is recommended to be set in the middle of the current range: Ioutage [ 2.7 A Thus the shunt resistor is calculated as: R3 = VT (K1) / Ioutage R3 = 81 mV/2.7 A = 30 mW. Comparator K1‘s reference voltage is matched to the characteristics of filament lam.


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