AN8353UB High Efficiency Car Dashboard Dimmer IC ■ Overview Unit : mm 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. 2.4±0.25 3.3±0.25 6.0±0.3 2.54 9 6 5 4 1.5±0.25 3 2 1 and high temperature checks reliability equivalent to the air bags requested in U.S. 1.4±0.3 30˚ • 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 : –40˚C to+100˚C • All products temperature cycle, high reliability by normal 0.5±0.1 23.3±0.3 7 1.5±0.25 8 ■ Features + 0.1 0.3 – 0.05 3.0±0.3 9-pin SIL Plastic Package (SIP009-P-0000C) ■ Block Diagram 4 9 3 Over Voltage Protector Control Voltage Conversion VCC 1 PWM Comparator Triangular Wave Gen. 6 5 2 7 8 GND ■ Pin Descriptions Pin No. Description Pin name 1 Output pin Outputs an intermittent source current at a duty proportional to an input voltage 2 GND GND 3 Input pin Applies a control voltage. 4 Noise eliminating capacity connection pin 1 Connect a capacitor to eliminator a noise. 5 Square wave output pin 6 Triangular wave output pin 7 Noise eliminating capacity connection pin 2 8 Standby pin 9 VCC 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 ■ Absolute Maximum Ratings (Ta=25˚C) Symbol Rating Supply voltage Parameter VCC 22 Unit V Power dissipation PD 550 mW Storage temperature Topr –40 to +100 ˚C Operating ambient temperature Tstg –50 to +150 ˚C ■ Recommended Operating Range (Ta=25˚C) Parameter Symbol Range VCC 8 to 18V Operating supply voltage range ■ Electrical Characteristics (Ta=25˚C) Parameter Symbol Condition Supply current ICC Eliminate CT and RT Oscillation frequency fosc 0% duty input voltage min typ max Unit 4 7.5 11 mA CT=0.027µF 90 115 140 Hz VIN – 0 CT=0.027µF 2 2.5 3 V 100% duty input voltage VIN– 100 CT=0.027µF 9.5 10 10.5 V Center duty (VCC=12V) D12V CT=0.027µF 35 45 55 % Center duty (VCC=8V) DD8V CT=0.027µF –1 0 1 % Center duty (VCC=18V) DD18V CT=0.027µF –1 0 1 % % Output duty gain DG CT=0.027µF 45 50 55 Output voltage at ON VON CT=2100pF 0.6 0.9 1.2 V IL CT=2100pF 0 4 µA Over voltage detection voltage VOV CT=2100pF 18 20 22 V Standby threshold voltage VSTH CT=2100pF 0.55 1.1 1.65 V Leakage current at OFF ■ Application Circuit • Bipolar Transister Output • MOS FET Output AN8353UB 1 2 3 4 5 6 AN8353UB 7 8 9 1 2 3 4 5 RT 180Ω (3W) 6 7 8 9 RT 0.1µF 0.1µF 0.1µF 0.1µF CT CT 0.056µF 0.056µF 180kΩ VR ± 22V + 33µF 20kΩ 180kΩ VR ± 22V + 33µF 20kΩ 10kΩ 2kΩ 10kΩ 1/fOSC=1.705RTCT 1/fOSC=1.705RTCT ■ 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 0.1µF C1 4 9 10kΩ 1 33µF Over voltage protection PWM comparator + Tranguian waveform generator 6 RT 5 – 2 7 8 0.1µF CT C2 STB Fig. 1 AN8353UB Block Diagram 2kΩ 3 Control voltage converting circuit Battery ± 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 ■ Supplementary Description (cont.) 1M VCC=12V VIN=6V • 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. 100% Turn-up Line Oscillation Frequency fOSC (Hz) 10k CT=0.001µF 1k CT=0.01µF CT=0.1µF 100 C (I) Duty 100k A CT=1µF 50% 10 1k 0.5 0% V4/V9 max V6/V9 V4/V9 V6/V9 A´ (VCC=12V) D1 100% DG D12V B´ t 10M • Duty D1 vs. Input Voltage VIN C´ 0.5 max V6/V9 1M V3/V9 (II) 1 100k Resistance RT (Ω) Fig. 3 Relations between Oscillation Frequency and CT and RT B (III) 10k 1 0.5 1 0 (IV) V3/V9 V1 TON Duty=TON · fOSC 1/fOSC t 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= IMΩ • Standby Threshold Voltage vs. Output D1 D1 50% 50% 0% 0% 0 VOV V9–2 VSTH V8–2