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| AN8353UB High Efficiency Car Dashboard Dimmer IC s Overview The AN8353UB is a dimmer IC to control illumination of the car dashboard at high efficiency and high performance by pulse width control. It outputs pulses at a duty proprotional to an input voltage. 2.40.25 3.30.25 6.00.3 Unit : mm 8 0.50.1 s Features * Low power consumption by pulse control * External ON/OFF control by the standby pin * Pulse frequency range : 50Hz to 10kHz * Built-in overvoltage protective circuit approx. 20V * Wide operating ambient temperature range : -40C to+100C * All products temperature cycle, high reliability by normal and high temperature checks reliability equivalent to the air bags requested in U.S. 23.30.3 7 6 5 4 1.50.25 2 1 0.3 - 0.05 + 0.1 3.00.3 9-pin SIL Plastic Package (SIP009-P-0000C) s Block Diagram 4 9 Over Voltage Protector PWM Comparator VCC 3 Control Voltage Conversion 1 Triangular Wave Gen. 2 GND 6 5 7 8 1.40.3 30 3 1.50.25 2.54 9 s Pin Descriptions Pin No. 1 2 3 4 5 Output pin GND Input pin Noise eliminating capacity connection pin 1 Square wave output pin Pin name GND Applies a control voltage. Connect a capacitor to eliminator a noise. Output a triangular wave, which serves as a reference for the PWM signal, to the Pin6 by connecting the resistor RT between the Pins5 and6, and capacity CT between the Pin6 and GND. Output a triangular wave, which serves as a reference for the PWM signal, to this pin by connecting the resistor RT between the Pins6 and 5, and capasity CT between the Pin6 and GND. Connect a capacitor to eliminator a noise. Forces to shut off an output current if a voltage higher than a threshold voltage of 1.1V is applied to the Pin8. Supply Voltage Description Outputs an intermittent source current at a duty proportional to an input voltage 6 7 8 9 Triangular wave output pin Noise eliminating capacity connection pin 2 Standby pin VCC s Absolute Maximum Ratings (Ta=25C) Parameter Supply voltage Power dissipation Storage temperature Operating ambient temperature Symbol VCC PD Topr Tstg Rating 22 550 -40 to +100 -50 to +150 Unit V mW C C s Recommended Operating Range (Ta=25C) Parameter Operating supply voltage range Symbol VCC Range 8 to 18V s Electrical Characteristics (Ta=25C) Parameter Supply current Oscillation frequency 0% duty input voltage 100% duty input voltage Center duty (VCC=12V) Center duty (VCC=8V) Center duty (VCC=18V) Output duty gain Output voltage at ON Leakage current at OFF Over voltage detection voltage Standby threshold voltage Symbol ICC fosc VIN - 0 VIN- 100 D12V DD8V DD18V DG VON IL VOV VSTH Condition Eliminate CT and RT CT=0.027F CT=0.027F CT=0.027F CT=0.027F CT=0.027F CT=0.027F CT=0.027F CT=2100pF CT=2100pF CT=2100pF CT=2100pF 18 0.55 min 4 90 2 9.5 35 -1 -1 45 0.6 typ 7.5 115 2.5 10 45 0 0 50 0.9 0 20 1.1 max 11 140 3 10.5 55 1 1 55 1.2 4 22 1.65 Unit mA Hz V V % % % % V A V V s Application Circuit * Bipolar Transister Output * MOS FET Output AN8353UB 1 2 3 4 5 6 7 8 9 1 2 3 AN8353UB 4 5 6 7 8 9 180 (3W) RT 0.1F CT 0.1F 0.1F RT 0.1F CT 0.056F 10k 1/fOSC=1.705RTCT 180k VR 20k 22V + 0.056F 33F 10k 2k 1/fOSC=1.705RTCT 180k VR 20k 22V + 33F s Supplementary Description * System Operational Principle The following describes the operational principle of the system using the AN8353UB. As shown in the block diagram in Fig. 1, a battery voltage is divided by the VR and input to the input Pin3 in accordance with rotation amount. The voltage at the output Pin1 is controlled by the AN8353UB so that the duty of the ON/OFF period of the external output transistor will be proportional to the input voltage, thus controlling a current flowing to the lamps of the dashboard, etc. to adjust their brightness. Since the output transistors are saturated at ON time and no current flows at OFF time, power consumption is low. The PWM method is used to control the output transistors. This method, as shown in Fig. 2 I/O Characteristic Chart (III), generates the triangular wave V 6 as a reference signal to generate pulses and input them to one end (Pin6) of the PWM comparator. The triangular wave frequency fOSC can be freely set from 50Hz to 10kHz, depending on the resistance value RT connected between the square wave output Pin5 and triangular wave output Pin6, and capacity value CT connected between the triangular wave output Pin6 and ground Pin2. The approximating expression for the then PWM frequency fOSC is ; 1/fOSC=1.705CTRT ******************************************************(1) For your refence, Fig. 3 shows the relations among CT, RT, and oscillation frequency fOSC. The voltage V4, whose voltage level is made matching the amplitude of the triangular wave by the control voltage converter, is given to the other input (Pin4) of the PWM comparator. That is, in Fig. 2 (II), the input voltage V3 is linearly converted into V4 by the control voltage converter so that the amplitude of the triangular wave will be about 20% to 80% of the input voltage input range (axis of abscissas in Fig. 2 (II)). Then, a current is supplied from the output Pin1 to turn on the output transistors during the period (TON) when the inverted input voltage is larger than the triangular wave. (Fig. 2 (II), (IV)) To the contrary, while the converted input voltage is smaller than the triangular wave, no current is supplied from the output Pin1 and the output transistors are turned off. The output pulse duty is expressed as follows. Duty=TON * fOSC ******************************************************(2) For the duty control characteristic of the output pulses to the input voltage V3, the duty of the output pulses is controlled from 0% to 100% at high-precision linearity while the "input voltage V3/supply voltage V9" is between about 4 Control voltage converting circuit 0.1F C1 9 3 33F + Tranguian waveform generator 6 RT CT 5 0.1F C2 STB 7 8 - 2 Fig. 1 AN8353UB Block Diagram 2k PWM comparator Over voltage protection 10k 1 Battery s Supplementary Description (cont.) * System Operational Principle (cont.) 0.2 (B-point) and 0.8 (C-point). The A-point in the figure shows the I/O characteristics when the "input voltage V3/supply voltage V9" is 0.7. And, when V3/V9 is from 0.05V to about 0.2V (B-point), the duty is controlled to 0%, and when V3/V9 is from 0.8V (C-point) to t.0V, the duty is controlled to 100%. The standby Pin8 can forcibly turn off the output transistors by applying a voltage of about 1.1V or more to this pin. When it is not necessary to forcibly turn off the output transistors, Leave the standby Pin8 open. 1M VCC=12V VIN=6V 100k Oscillation Frequency fOSC (Hz) 10k 1k CT=0.001F CT=0.01F 100 CT=0.1F 100% Turn-up Line Duty (I) A C CT=1F 50% 10 1k 0% B (III) max V6/V9 V4/V9 V6/V9 max V6/V9 t V4/V9 1 (II) A 0.5 B 0.5 (IV) V1 TON 1/fOSC t Duty=TON * fOSC 0 V3/V9 DG D12V 1 V3/V9 0.5 1 10k 100k 1M 10M Resistance RT () Fig. 3 Relations between Oscillation Frequency and CT and RT * Duty D1 vs. Input Voltage VIN C D1 100% (VCC=12V) Fig. 2 I/O Characteristic Chart 0% VIN-0 4V 6V 8V VIN-100 VIN * Output voltage at ON VON VON=VCC -V1-2 * Over voltage Detecting Voltage vs. Output * Leakage current at OFF V 1-2 IL= IM * Standby Threshold Voltage vs. Output D1 D1 50% 50% 0% VOV V9-2 0% 0 VSTH V8-2 |
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