U643B_05 ATMEL | Alldatasheet
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- Temperature and Supply Voltage Compensated Flashing Frequency Frequency Doubling Indicates Lamp Outage Relay Driver Output with High Current Carrying Capacity and Low Saturation Voltage Minimum Lamp Load for Flasher Operation: ≥ 1W Very Low Susceptibility to EMI Protection According to ISO/TR 7637/1 Level 4 1. Description The bipolar integrated circuit U643B is used in relay-controlled automotive flashers where a high-level EMC is required. Lamp outage is indicated by frequency doubling during hazard warning as well as direction mode. Flasher IC with 30-mΩ Shunt U643B Rev. 4727B–AUTO–09/05
4727B–AUTO–09/05 U643B 2. Block Diagram Figure 2-1. Car Flasher Application Circuit, Resistor R1 and R2: 0.25W; R4 for Protection Against Continuous Reversed Polarity: 0.5W V6-81 mV 20 kΩ 5 kΩ 20 kΩ 5 kΩ 23 V Pulse generator IC Ground 20 kΩ Relay + V S + 49 470 Ω 49 a 6 2 49 a-Comparator K 3 49 a-Comparator K 2
21 W 21 W 5 W21 W21 W5 W
- 31 Indicator lamps Measuring comparator K 1 Shunt 30 mΩ
4727B–AUTO–09/05 U643B 3. Pin Configuration Figure 3-1. Pinning GND REL OSC SI LD VS OSC U643B VS Table 3-1. Pin Description Pin Symbol Function
1 GND IC ground
2 VS Supply voltage V
S
3 REL Relay driver
1 Oscillator
6 VS Supply voltage V S
7 LD Lamp failure detection
8 SI Start input (49a)
4727B–AUTO–09/05 U643B 4. Functional Description
4.1 Pin 1, GND
The U643B is protected against damage in case of battery reversal via resistor R 4 to ground (–31). An integrated protection circuit together with external resistances R2 and R4 limits the cur- rent pulses in the IC.
4.2 Pin 2, Supply Voltage, V S Power
The arrangement of the supply connections to pin 2 must be so as to ensure that on the connec- tion printed circuit board (PCB), the resistance of VS to pin 6 is lower than that to pin 2.
4.3 Pin 3, Relay Control Output (Driver)
The relay control output is a high-side driver with a low saturation voltage. It is capable of driving a typical automotive relay with a minimum coil resistance of 60Ω.
4.4 Pin 4 and 5, Oscillator
The flashing frequency, f1, is determined by the R1C1 components as given by the formula below (see Figure 2-1 on page 2): where C1 ≤ 47 µF, R1 = 6.8 kΩ to 510 kΩ In case of a lamp outage (see pin 7) the oscillator frequency is switched to the lamp outage fre- quency f2 with f2 ≈ 2.2 × f1. Duty cycle in normal flashing mode: 50% Duty cycle in lamp outage mode: 40% (bright phase)
4.5 Pin 6, Supply Voltage, Sense
For accurate monitoring via the shunt resist or, a minimized layer resistance from point V S/shunt to pin 6 is recommended.
4727B–AUTO–09/05 U643B
4.6 Pin 7, Lamp Outage Detection
The lamp current is monitored via an external shunt resistor R 3 and an internal comparator K1 with its reference voltage of typically 81 mV (V S = 12V). The outage of one lamp is detected according to the following calculation: Nominal current of 1 lamp: 21W / (VS = 12V): Ilamp = 1.75A Nominal current of 2 lamps: 2 × 21W / (VS = 12V): Ilamp = 3.5A. The detection threshold should be set in the middle of the current range: Ioutage ≈ 2.7A Thus, the shunt resistor is calculated as: R3 = VT (K1) / Ioutage R3 = 81 mV/2.7A = 30 mΩ Comparator K1's reference voltage is matched to the characteristics of filament lamps (see Con- trol Signal Threshold in “Electrical Characteristics” on page 6). The combination of shunt resistor and resistance of wire harness prevents pin 7 from a too high voltage in the case of shorted lamps.
4.7 Pin 8, Start Input
Start condition for flashing: the voltage at pin 8 has to be below K3 threshold (flasher switch closed). Humidity and dirt may decrease the resistance between 49a and GND. If this leakage resistance is > 5 kΩ, the IC still remains in the OFF condition. In this case the voltage at pin 8 is between the thresholds of comparators K2 and K3. During the bright phase the voltage at pin 8 is above the K2 threshold, during the dark phase it is below the K3 threshold. For proper start conditions a minimum lamp wattage of 1W is required.
4727B–AUTO–09/05 U643B 5. Absolute Maximum Ratings Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Reference point pin 1 Parameters Symbol Value Unit Supply voltage Pins 2 and 6 V S 16.5 V Surge Forward Current tP = 0.1 ms tP = 300 ms tP = 300 ms Pins 2 and 6 Pins 2 and 6 Pin 8 IFSM IFSM IFSM 1.5 1.0 A A mA Output current Pin 3 I O 0.3 A Power Dissipation Tamb = 95°C T amb = 60°C DIP 8 SO8 DIP 8 SO8 Ptot Ptot Ptot Ptot 420 340 690 560 mW mW mW mW Junction temperature T J 150 °C Ambient temperature range T amb –40 to +95 °C Storage temperature range T stg –55 to +150 °C 6. Thermal Resistance Parameters Symbol Value Unit Junction ambient DIP8 SO8 RthJA RthJA 110 160 K/W K/W 7. Electrical Characteristics Typical values under normal operation in application circuit (see Figure 2-1 on page 2), VS (+49, pin 2 and 6) = 12V. Reference point ground (–31), Tamb = 25°C, unless otherwise specified. Parameters Test Conditions Symbol Min. Typ. Max. Unit Supply voltage range Pins 2 and 6 V S (+49) 9 to 15 V Supply current Pins 2 and 6 Dark phase Bright phase IS IS 4.5 7.0 mA mA Relay output: Saturation voltage Reverse current Pin 3 IO = 150 mA, VS = 9V with resistance = 60Ω VO IO 1.0 0.1 V mA Start delay First bright phase t on 10 ms Frequency tolerance δf1 –5 +5 % Bright period Basic frequency f1 Control frequency f2 ∆f1 ∆f2 Frequency increase Lamp outage f 2 2.15 f1 2.3 f1 Hz Control signal threshold VS = 15V, pin 7 VS = 9V, pin 7 VS = 12V, pin 7 VR3 VR3 VR3 mV mV mV Leakage resistance 49a to GND R P 45 k Ω Lamp load PL 1W
4727B–AUTO–09/05 U643B 9. Package Information
9.1 DIP8
- Ordering Information Extended Type Number Package Remarks U643B-MY DIP8 Pb-free U643B-MFPY SO8 Tubed, Pb-free U643B-MFPG3Y SO8 Taped and reeled, Pb-free
4727B–AUTO–09/05 U643B
9.2 SO8
- Revision History technical drawings according to DIN specifications Dimensions in mm 5.00 4.85 0.4 1.27 3.81 1.4 0.25 0.10 5.2 4.8 3.7 3.8 6.15 5.85 0.2 Please note that the following page numbers referred to in this section refer to the specific revision mentioned, not to this document. Revision No. History 4727B-AUTO-09/05
- Put datasheet in a new template
- Updated text to new style guide
- First page: Pb-free logo added
- Page 6: Ordering Information changed
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