Features • • • • • • • Pulse-width Modulation up to 2 kHz Clock Frequency Protection against Short-circuit, Load-dump Overvoltage and Reverse VS Duty-cycle 0 to 100% Continuously Output Stage for Power MOSFET Interference and Damage Protection According to VDE 0839 and ISO/TR 7637/1 Charge-pump Noise Suppressed Ground-wire Breakage Protection Description The U6084B is a PWM-IC with bipolar technology designed for the control of an N-channel power MOSFET used as a high-side switch. The IC is ideal for use in the brightness control (dimming) of lamps such as in dashboard applications. For constant brightness, the preselected duty-cycle can be reduced automatically as a function of the supply voltage. PWM Power Control with Automatic Duty-cycle Reduction Figure 1. Block Diagram with External Circuit VBatt C5 VS 9 16 Rsh 11 Short circuit latch monitoring U6084B Current monitoring + short circuit detection 12 5 Charge 13 pump RC oscillator 6 PWM C1 47 kΩ C2 47 nF Logic 3 14 Control input Duty cycle range 0-100% C3 Output Duty cycle reduction Voltage monitoring 4 1 150 Ω Enable/ disable 2 R3 Ground Rev. 4677B–AUTO–02/04 Pin Configuration Figure 2. Pinning GND 1 16 VS EN/DIS 2 15 NC VI 3 14 OUTPUT REDUCT 4 13 2 VS NC 5 12 SENSE OSC 6 11 DELAY NC 7 10 NC NC 8 9 LATCH Pin Description 2 Pin Symbol Function 1 GND IC ground 2 EN/DIS 3 VI 4 REDUCT 5 NC 6 OSC 7 NC Enable/disable Control input (duty cycle) Duty cycle reduction Attenuation Oscillator Not connected 8 NC 9 LATCH Not connected 10 NC 11 DELAY 12 SENSE Current sensing 13 2VS Voltage doubler 14 OUTPUT 15 NC Not connected 16 VS Supply voltage VS Status short-circuit latch Not connected Short-circuit protection delay Output U6084B 4677B–AUTO–02/04 U6084B Functional Description Pin1 – GND Ground-wire Breakage To protect the FET in case of ground-wire breakage, a 820 kΩ resistor between gate and source is recommended to provide proper switch-off conditions. Pin 2 – Enable/Disable The dimmer can be switched on or off, with pin 2, independently of the set duty cycle. Table 1. Pin 2 Function V2 Pin 3 – Control Input Function Approximately > 0.7 V or open Disable < 0.7 V or connected to pin 1 Enable The pulse width is controlled by means of an external potentiometer (47 kΩ). The characteristic (angle of rotation/duty cycle) is linear. The duty cycle be varied from 0 to 100%. It is possible to further restrict the duty cycle with resistors R1 and R2 (see Figure 3 on page 8). Pin 3 is protected against short-circuit to VBatt and ground GND (VBatt ≤16.5 V). Pin 4 – Duty Cycle Reduction With pin 4 connected according to Figure 3 on page 8, the set duty cycle is reduced to VBatt ≈ 12.5 V. This causes a power reduction in the FET and in the lamps. In addition, the brightness of the lamps is largely independent of the supply voltage range, VBatt = 12.5 to 16 V. Output Slope Control The rise and fall time (tr, tf) of the lamp voltage can be limited to reduce radio interference. This is done with an integrator which controls a power MOSFET as source follower. The slope time is controlled by an external capacitor C4 and the oscillator current (see Figure 3 on page 8). Calculation: C4 t f = t r = VBatt × --------I osc With VBatt = 12 V, C4 = 470 pF and Iosc = 40 µA, we thus obtain a controlled slope of 470 pF t f = t r = 12 V × ------------------ × 141 µs 40 µA Pin 5 – Attenuation Capacitor C4 connected to pin 5 damps oscillation tendencies. Pin 6 – Oscillator The oscillator determines the frequency of the output voltage. This is defined by an external capacitor, C2. It is charged with a constant current, I, until the upper switching threshold is reached. A second current source is then activated which taps a double current, 2 × I, from the charging current. The capacitor, C2 , is thus discharged by the current, I, until the lower switching threshold is reached. The second source is then switched off again and the procedure starts once more. 3 4677B–AUTO–02/04 Example for Oscillator Frequency Calculation V T100 = VS × α1 = ( V Batt – IS × R 3 ) × α1 V T<100 = VS × α2 = ( V Batt – IS × R 3 ) × α2 V TL = V S × α3 = ( V Batt – IS × R 3 ) × α3 where VT100 = High switching threshold 100% duty cycle VT<100 = High switching threshold < 100% duty cycle VTL = Low switching threshold α1, α2 and α3 are fixed values The above mentioned threshold voltages are calculated for the following values given in the datasheet. VBatt = 12 V, IS = 4 mA, R3 = 150 Ω, α1 = 0.7, α2 = 0.67 and α3 = 0.28. VT100 = (12 V - 4 mA × 150 Ω) × 0.7 ≈ 8 V VT<100 = 11.4 V × 0.67 = 7.6 V VTL = 11.4 V × 0.28 = 3.2 V For a duty cycle of 100%, the oscillator frequency, f, is as follows: I osc f = ----------------------------------------------------------- where C2 = 22 nF and Iosc = 40 µA 2 × ( V T100 – VTL ) × C 2 Therefore: 40 µA f = ------------------------------------------------------------------- = 189 Hz 2 × ( 8 V – 3.2 V ) × 22 nF For a duty cycle of less than 100%, the oscillator frequency, f, is as follows: I osc f = ---------------------------------------------------------------------------------------------------------2 × ( V T<100 – V TL ) × C 2 + 4 × V Batt × C 4 where C4 = 470 pF 40 µA f = ------------------------------------------------------------------------------------------------------------------------------- = 185 Hz 2 × ( 7.6 V – 3.2 V ) × 22 nF + 4 × 12 V × 470 pF A selection of different values of C2 and C4 provides a range of oscillator frequencies from 10 to 2000 Hz. Pins 7, 8, 10 and 15 Not connected. Pin 9 – Status Short Circuit Latch The status of the short-circuit latch can be monitored via pin 9 (open collector output). Table 2. Pin 9 Function 4 Pin 9 Function L Short-circuit detected H Not short-circuit detected U6084B 4677B–AUTO–02/04 U6084B Pins 11 and 12 – Short-circuit Protection and Current Sensing Short-circuit Detection and Time Delay td The lamp current is monitored by means of an external shunt resistor. If the lamp current exceeds the threshold for the short-circuit detection circuit (VT2 ≈ 90 mV), the duty cycle is switched over to 100% and capacitor C5 is charged by a current source of 20 µA (Ich - Idis). The external FET is switched off after the cut-off threshold (VT11) is reached. Renewed switching on the FET is possible only after a power-on reset. The current source, Idis, ensures that capacitor C5 is not charged by parasitic currents. Capacitor C5 is discharged by Idis to typ. 0.7 V. Time delay, td, is as follows: ( V 11 – 0.7 V ) t d = C 5 × ---------------------------------( Ich – Idis ) With C5 = 330 nF and VBatt = 12 V, we have ( 9.8 V – 0.7 V ) t d = 330 nF × -------------------------------------- = 150 ms 20 µA Current Limitation The lamp current is limited by a control amplifier that protects the external power transistor. The voltage drop across an external shunt resistor acts as the measured variable. Current limitation takes place for a voltage drop of VT1 ≈ 100 mV. Owing to the difference VT - VT2 ≈ 10 mV, current limitation occurs only when the short-circuit detection circuit has responded. After a power-on reset, the output is inactive for half an oscillator cycle. During this time, the supply voltage capacitor can be charged so that current limitation is guaranteed in the event of a short-circuit when the IC is switched on for the first time. Pins 13 and 14 – Charge Pump and Output Pin 14 (output) is suitable for controlling a power MOSFET. During the active integration phase, the supply current of the operational amplifier is mainly supplied by capacitor C3 (bootstrapping). Additionally, a trickle charge is generated by an integrated oscillator (f13 ≈ 400 kHz) and a voltage doubler circuit. This permits a gate voltage supply at a duty cycle of 100%. Pin 16 – Supply Voltage, Vs or VBatt Undervoltage Detection In the event of voltages of approximately VBatt < 5.0 V, the external FET is switched off and the latch for short-circuit detection is reset. A hysteresis ensures that the FET is switched on again at approximately VBatt ≥ 5.4 V. Overvoltage Detection Stage 1 If overvoltages of VBatt > 20 V (typically) occur, the external transistor is switched off and switched on again at VBatt < 18.5 V (hysteresis). Stage 2 If VBatt > 28.5 V (typically), the voltage limitation of the IC is reduced from 26 V to 20 V. The gate of the external transistor remains at the potential of the IC ground, thus producing voltage sharing between the FET and lamps in the event of overvoltage pulses (e.g., load-dump). The short-circuit protection is not in operation. At VBatt < 23 V, the overvoltage detection stage 2 is switched off. 5 4677B–AUTO–02/04 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 Parameters Symbol Value Unit Tj 150 °C Ambient temperature range Tamb -40 to +110 °C Storage temperature range Tstg -55 to +125 °C Symbol Value Unit RthJA 120 K/W Junction temperature Thermal Resistance Parameters Junction ambient Electrical Characteristics Tamb = -40 to +110°C, VBatt = 9 to 16.5 V, (basic function is guaranteed between 6.0 V to 9.0 V) reference point ground, unless otherwise specified (see Figure 1 on page 1). All other values refer to pin GND (pin 1). Parameters Test Conditions Current consumption Pin 16 Supply voltage Overvoltage detection, stage 1 Stabilized voltage IS = 10 mA, pin 16 Battery undervoltage detection - on - off Symbol Min. Typ. IS 24.5 VBatt 4.4 4.8 Unit 6.8 mA 25 V 27.0 V 5.0 5.4 5.6 6.0 V VBatt VS Max. Battery Overvoltage Detection Pin 2 Stage 1: - on - off VBatt 18.3 16.7 20.0 18.5 21.7 20.3 V Stage 2: - on - off VBatt 25.5 19.5 28.5 23.0 32.5 26.5 V Stabilized voltage IS = 30 mA, pin 16 VZ 18.5 20.0 21.5 V Short-circuit Protection Pin 12 Short-circuit current limitation VT1 = VS - V12 VT1 85 100 120 mV Short-circuit detection VT2 = VS - V12 Delay Timer Short-circuit Detection Pin 11 Switched off threshold VT11 = VS - V11 VT2 75 90 105 mV VT1 - VT2 3 10 30 mV VT11 9.5 9.8 10.1 V Charge current Ich 23 µA Discharge current Idis 3 µA Capacitance current I5 = Ich - Idis Output short-circuit latch Pin 9 Saturation voltage I9 = 100 µA Notes: 6 I5 Vsat 13 20 27 mA 150 350 mV 1. Reference point is battery ground U6084B 4677B–AUTO–02/04 U6084B Electrical Characteristics (Continued) Tamb = -40 to +110°C, VBatt = 9 to 16.5 V, (basic function is guaranteed between 6.0 V to 9.0 V) reference point ground, unless otherwise specified (see Figure 1 on page 1). All other values refer to pin GND (pin 1). Parameters Test Conditions Symbol Min. Voltage Doubler Pin 13 Voltage Duty cycle 100% V13 2 VS f13 I13 = 5 mA (whichever is lower) Oscillator frequency Internal voltage limitation Gate Output Typ. Max. Unit 280 400 520 kHz V13 26 27.5 30.0 V V13 (VS+14) (VS+15) (VS+16) V14 0.35 0.70 0.95 Pin 14 Low level VBatt = 16.5 V, Tamb = 110°C, R3 = 150 Ω Voltage Current 1.5(1) High level, duty cycle 100% V14 V14 = Low level I14 V14 = High level, I13 > I14 Enable/Disable Pin 2 Current V2 = 0 V Duty Cycle Reduction Pin 4 Z-voltage I4 = 500 µA V V13 1.0 mA -1.0 I2 -20 -40 -60 µA V4 6.9 7.4 8.0 V f 10 2000 Hz Oscillator Frequency Pin6 Threshold cycle Upper V T100 V 14 = High, α1 = -------------VS α1 0.68 0.7 0.72 V T<100 V 14 = Low, α2 = ---------------VS α2 0.65 0.67 0.69 V TL α3 = -------VS α3 0.26 0.28 0.3 ±Iosc 26 40 54 µA f 6.0 9.9 13.5 Hz Lower Oscillator current VBatt = 12 V Frequency tolerance C4 open, C2 = 470 nF, duty cycle = 50% Notes: 1. Reference point is battery ground 7 4677B–AUTO–02/04 8 22 nF 47 µF C1 R2 C2 C6 47 kΩ R1 I 30 k Ω VS VS 4 3 6 100 Ω 5 Reset Low voltage monitoring + - + - Reset Switch - on delay Overvoltage monitoring stage 1 2I Oscillator VS VS 2 Reset - + VS VS C5 Idis 11 150 Ω Ich VS 330 nF VS 1 Ground R3 7 9 NC Overvoltage monitoring stage 2 16 NC 8 NC Current limiting - + VS 10 NC 15 14 13 12 10 mV 90 mV Voltage doubler VS C4 820 kΩ 47 pF Load RL RSh 47 nF C3 VBatt Figure 3. Application U6084B 4677B–AUTO–02/04 U6084B Ordering Information Extended Type Number Package U6084B-FP Remarks SO16 – Package Information Package SO16 Dimensions in mm 5.2 4.8 10.0 9.85 3.7 1.4 0.25 0.10 0.4 1.27 6.15 5.85 8.89 16 0.2 3.8 9 technical drawings according to DIN specifications 1 8 Revision History Please note that the referring page numbers in this section are referred to the specific revision mentioned, not to this document. Changes from Rev. 4677A - 02/03 to Rev. 4677B - 02/04 1. Block Diagram on page 1 changed. 2. New heading rows at Table “Absolute Maximum Ratings” on page 6 added. 9 4677B–AUTO–02/04 Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 487-2600 Regional Headquarters Europe Atmel Sarl Route des Arsenaux 41 Case Postale 80 CH-1705 Fribourg Switzerland Tel: (41) 26-426-5555 Fax: (41) 26-426-5500 Asia Room 1219 Chinachem Golden Plaza 77 Mody Road Tsimshatsui East Kowloon Hong Kong Tel: (852) 2721-9778 Fax: (852) 2722-1369 Japan 9F, Tonetsu Shinkawa Bldg. 1-24-8 Shinkawa Chuo-ku, Tokyo 104-0033 Japan Tel: (81) 3-3523-3551 Fax: (81) 3-3523-7581 Atmel Operations Memory 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 436-4314 RF/Automotive Theresienstrasse 2 Postfach 3535 74025 Heilbronn, Germany Tel: (49) 71-31-67-0 Fax: (49) 71-31-67-2340 Microcontrollers 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 436-4314 La Chantrerie BP 70602 44306 Nantes Cedex 3, France Tel: (33) 2-40-18-18-18 Fax: (33) 2-40-18-19-60 ASIC/ASSP/Smart Cards 1150 East Cheyenne Mtn. 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