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U6083B
PWM Power Control with Interference Suppression
Description
The U6083B is a PWM IC in bipolar technology for the control of an N-channel power MOSFET used as a highside switch. The IC is ideal for use in the brightness control (dimming) of lamps e.g., in dashboard applications.
Features
D Pulse-width modulation up to 2 kHz clock frequency D Protection against short circuit, load dump over-voltage and reverse VS D Duty cycle 18 to 100% continuously D Internally reduced pulse slope of lamp's voltage D Interference and damage protection according to VDE 0839 and ISO/TR 7637/1. D Charge-pump noise suppressed D Ground-wire breakage protection
Block Diagram
VS 1 5 Current monitoring + short circuit detection 6 C5 Rsh VBatt
C1 47 kW C2
4
RC oscillator PWM Logic Control input
Charge pump
7 C3 47 nF 8
3
Output
Duty cycle range 18 ... 100%
Duty cycle reduction GND 2
Voltage monitoring
Slew rate control
95 9753
150 W
R3 Ground
Figure 1. Block diagram with external circuit
Ordering Information
Extended Type Number U6083B Package DIP8 Remarks
Rev. A3, 11-Apr-01
1 (9)
U6083B
Pin Description
VS GND VI Osc 1 2 3 4
95 9944
8 7 6 5
Output 2 VS Sense Delay
Pin 1 2 3 4 5 6 7 8
Symbol VS GND VI Osc Delay Sense 2 VS Output
Function Supply voltage VS IC ground Control input (duty cycle) Oscillator Short circuit protection delay Current sensing Voltage doubler Output
Functional Description
Pin 1, Supply Voltage, Vs or VBatt
Overvoltage Detection Stage 1: If overvoltages VBatt > 20 V (typ.) occur, the external transistor is switched off and switched on again at VBatt < 18.5 V (hysteresis). Stage 2: If VBatt > 28.5 V (typ), the voltage limitation of the IC is reduced from VS = 26 V to 20 V. The gate of the external transistor remains at the potential of the IC ground, thus producing voltage sharing between FET and lamps in the event of overvoltage pulses occuring (e.g., load dump). The short-circuit protection is not in operation. At VBatt approx. < 23 V, the overvoltage detection stage 2 is switched off. Thus during overvoltage detection stage 2 the lamp voltage Vlamp is calculated to : VLamp = VBatt - VS - VGS VS = Supply voltage of the IC at overvoltage detection stage 2 VGS = Gate - source voltage of the FET Undervoltage Detection In the event of voltages of approximately VBatt < 5.0 V, the external FET is switched off and the latch for shortcircuit detection is reset. A hysteresis ensures that the FET is switched on again at approximately VBatt 5.4 V.
Pin 3, Control Input
The pulse width is controlled by means of an external potentiometer (47 kW). The characteristic (angle of rotation/duty cycle) is linear. The duty cycle can be varied from 18 to 100%. It is possible to further restrict the duty cycle with the resistors R1 and R2 (see figure 3). In order to reduce the power dissipation of the FET and to increase the lifetime of the lamps, the IC automatically reduces the maximum duty cycle at Pin 8 if the supply voltage exceeds V2 = 13 V. Pin 3 is protected against short-circuit to VBatt and ground (VBatt x 16.5 V).
Pin 4, 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 at the current, I, until the lower switching threshold is reached. The second source is then switched off again and the procedure starts once more. Example for Oscillator Frequency Calculation: Switching thresholds VT100 = High switching threshold (100% duty cycle) VT100 = VS a1 = (VBatt - IS R3) a1 VT<100 = High switching threshold (< 100% duty cycle) VT<100 = VS a2 = (VBatt - IS R3) a2 VTL = Low switching threshold VTL = VS a3 = (VBatt - IS R3) a3 whereas a1, a2 and a3 are fixed values.
Pin 2, GND
Ground-Wire Breakage To protect the FET in the case of ground-wire breakage, a 1 MW resistor between gate and source it is recommended to provide proper switch-off conditions.
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Rev. A3, 11-Apr-01
U6083B
Calculation Example The above mentioned threshold voltages are calculated for the following values given in the data sheet. VBatt = 12 V, IS = 4 mA, R3 = 150 W , a1 = 0.7, a2 = 0.67 and a3 = 0.28. VT100 = (12 V - 4 mA VT<100 = 11.4 V VTL = 11.4 V 150 W) 0.7 [ 8 V 0.67 = 7.6 V 0.28 = 3.2 V dV8/dt = a4 dV4/dt = (VBatt - IS 2 a4 f (a2 - a3) when f = 75 Hz, VTX = VT < 100 and a4 = 63 we obtain
dV8/dt=2 63 = 42 V/ms
R3)
75 Hz (0.67-0.28) (12 V-4 mA 15 W)
Via an external capacitor, C4, the slope can be further reduced as follows: dV8/dt = IOSC/(C4 + C2/a4) when IOSC = 45 mA, C4 = 1.8 nF, C2 = 68 nF and a4 = 63 then dV8/dt = 45 mA/(1.8 nF + 68 nF/63) = 15.6 V/ms To damp oscillation tendencies, a resistance of 100 W in series with capacitance C4 is recommended.
Oscillator Frequency 3 cases have to be distinguished 1) f1 + f1 for duty cycle = 100%, no slope reduction with capacitor C4 (see figure 3) 2 Iosc (VT100 * VTL) C2 , where C2 + 68 nF I osc + 45 mA
f 1 + ... + 75 Hz 2) f2 for duty cycle < 100%, no slope reduction with capacitor C4
Interference Suppression
"On-board" radio reception according to VDE 0879 part 3/4.81 Test conditions refering to figure 2. Application circuit according to figure 1 or 3. Load: nine 4-W lamps in parallel. Duty cycle VBatt fOsc = 18% = 12 V = 100 Hz
For a duty cycle of less than 100%, the oscillator frequency, f, is as follows:
f2 + 2 Iosc V Tt100 * V TL C2 , where C 2 + 68 nF I osc + 45 mA
f 2 + ... + 69Hz 3) f3 + f3 with duty cycle < 100% with slope reduction capacitor C4 (see page 3 "Output Slope Control") 2 I osc (VTt100 * VTL) C 2 ) 2V Batt C4
where C 2 + 68 nF C 4 + 1.8 nF I osc + 45 mA f 3 + ... + 70 Hz By selecting different values of C2 and C4, it is possible to have a range of oscillator frequencies from 10 to 2000 Hz as shown in the data sheet.
Output Slope Control
The slope of the lamp voltage is internally limited to reduce radio interference by limitation of the voltage gain of the PWM comparator. Thus, the voltage rise on the lamp is proportional to the oscillator voltage increase at the switchover time according to the equation.
Figure 2. Voltage spectrum of on-board radio reception
Rev. A3, 11-Apr-01
3 (9)
U6083B
Pins 5 and Pin 6, Short-Circuit Protection and Current Sensing
1. 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 the capacitor C5 is charged by a current source of Ich - Idis. The external FET is switched off after the cut-off threshold (VT5) is reached. Renewed switching on of the FET is possible only after a power-on reset. The current source, Idis, ensures that the capacitor C5 is not charged by parasitic currents. Time delay, td, is as follows: td = C5 VT5/ (Ich - Idis) With C5 = 100 nF and VT5 = 10.4 V, Ich =13 mA, Idis = 3 mA, we have td = 100 nF td = 104 ms 10.4 V/ (13 mA - 3 mA) 2. Current Limitation: The lamp current is limited by a control amplifier to protect 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 VT1-VT2 10 mV, it is ensured that 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 7 and 8, Charge Pump and Output,
Pin 8 (output) is suitable for controlling a power MOSFET. During the active integration phase, the supply current of the operational amplifier is mainly supplied by the capacitor C3 (bootstrapping). In addition, a trickle charge is generated by an integrated oscillator (f7 400 kHz) and a voltage doubler circuit. This permits a gate voltage supply at a duty cycle of 100%.
Absolute Maximum Ratings
Parameters Junction temperature Ambient temperature range Storage temperature range Symbol Tj Tamb Tstg Value 150 -40 to +110 -55 to +125 Unit C C C
Thermal Resistance
Parameters Junction ambient Symbol RthJA Value 120 Unit K/W
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Rev. A3, 11-Apr-01
U6083B
Electrical Characteristics
Tamb = -40 to +110C, 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). All other values refer to Pin GND (Pin 2). Parameters Current consumption Supply voltage Stabilized voltage Battery undervoltage detection Test Conditions / Pins Pin 1 Overvoltage detection, stage 1 IS = 10 mA - on - off Pin 1 Symbol IS VBatt Vs VBatt 24.5 4.4 4.8 5.0 5.4 Min. Typ. Max. 7.9 25 27.0 5.6 6.0 Unit mA V V V
Battery overvoltage detection Stage 1: Stage 2: Detection stage 2 Stabilized voltage Short-circuit protection Short-circuit current limitation Short-circuit detection VT1 = VS - V6 VT2 = VS - V6 - on - off - on - off IS = 30 mA Pin 1 Pin 6 VT1 VT2 VT1 - VT2 Delay timer short circuit detection, VBatt = 12 V Pin 5 Switched off threshold Charge current Discharge current Capacitance current Voltage doubler Voltage Oscillator frequency Internal voltage limitation I7 = 5 mA (whichever i lower) ( hi h is l ) Edge steepness dv8/dt =a4 dV4/dt dV8/dtmax Duty cycle 100% I5 = Ich - Idis Pin 7 V7 f7 V7 a4 2 VS 280 26 VS+14 53 400 27.5 VS+15 63 520 30.0 VS+16 72 130 V/ms kHz V VT5 = VS - V5 VT5 Ich Idis I5 5 10.2 10.4 13 3 10 15 10.6 V mA mA mA 85 75 3 100 90 10 120 105 30 mV mV VBatt VBatt Vs 18.3 16.7 25.5 19.5 18.5 20.0 18.5 28.5 23.0 20.0 21.7 20.3 32.5 26.5 21.5 V V V V V
*)
Reference point is battery ground.
Rev. A3, 11-Apr-01
5 (9)
U6083B
Electrical Characteristics (continued)
Tamb = -40 to +110C, 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). All other values refer to Pin GND (Pin 2). Parameters Gate output Voltage Low level VBatt = 16.5 V Tamb = 110C, R3 = 150 W High level, duty cycle 100% Current V8 = Low level V8 = High level, I7 > | I8 | Duty cycle Min: C2 = 68 nF Max: VBatt v 12.4 V VBatt = 16.5 V, C2 = 68 nF Pin4 V 8 + High, a1 + V 8 + Low, a2 + Lower L a3 + Oscillator current Frequency VTL VS V T100 VS V Tt100 VS tp/T V8 I8 1.0 -1.0 15 100 65 18 73 21 % 81 V7 mA Test Conditions / Pins Pin 8 V8 0.35 0.70 0.95 1.5 *) V Symbol Min. Typ. Max. Unit
Oscillator Frequency Threshold cycle Upper f a1 a2 a3 Iosc f 10 0.68 0.65 0.26 34 56 0.7 0.67 0.28 45 75 2000 0.72 0.69 0.3 54 90 mA Hz Hz
VBatt = 12 V C4 open, C2 = 68 nF duty cycle = 50%
*)
Reference point is battery ground.
6 (9)
Rev. A3, 11-Apr-01
Application
VBatt
C5 100 nF 5 VS VS 90 mV Ich 10 mV 6 Idis - + Reset Switch - on delay 63 x R R 7 C3 47 nF Overvoltage monitoring stage 2 Overvoltage monitoring stage 1 Reset Low voltage monitoring 8 1 MW Reset VS Voltage doubler C4 1.8 nF + - Current limiting VS VS Rsh VS VS 1
Rev. A3, 11-Apr-01
- I + Oscillator + - GND 2 150 W R3 Ground Load RL
R1
4
C1
47 mF
C2
68 nF
2I
Figure 3. Application
VS
47 kW 3
R2
VS
VS
U6083B
95 9758
7 (9)
U6083B
Package Information
Package DIP8
Dimensions in mm
9.8 9.5 1.64 1.44 7.77 7.47
4.8 max 6.4 max 0.5 min 0.58 0.48 7.62 8 5 2.54 3.3 0.36 max 9.8 8.2
technical drawings according to DIN specifications 13021
1
4
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Rev. A3, 11-Apr-01
U6083B
Ozone Depleting Substances Policy Statement
It is the policy of Atmel Germany 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. Atmel Germany GmbH 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. Atmel Germany GmbH 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 Atmel Wireless & Microcontrollers products for any unintended or unauthorized application, the buyer shall indemnify Atmel Wireless & Microcontrollers 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. Data sheets can also be retrieved from the Internet: http://www.atmel-wm.com
Atmel Germany GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany Telephone: 49 (0)7131 67 2594, Fax number: 49 (0)7131 67 2423
Rev. A3, 11-Apr-01
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