ADT7110 ADTECH | Alldatasheet

Document overview

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Technical content

Features

Typical Application Circuit

Applications

  • Input voltage range : 10.5V to 15V
  • Current mode PWM controller with integrated compensation components
  • 350mA output load current available
  • Built-in chip enable/disable function
  • Built-in current limit protection
  • 500kHz fixed frequency internal oscillator
  • Small outline SOT-26 package (2.9mm x 1.6mm body)
  • Infrared LED driver for CCD camera 1 2 3 6 5 4 A11 RS GND PWM VIN EN FB EN VIN RSE A11 RFB1a RFB1b RFB1c RFB1d RFB1e RFB1f RLED6 RLED5 RLED4 RLED3 RLED2 RLED1 RFB2 VFB VOUT

Jun. 07. 2008 / Rev. 0.1 ADT7110 * This specifications are subject to be changed without notice http://www.ad-tech.co.kr Part List Component Description Type Value U1*1 Composite type with a PNP transistor and schottky barrier diode IC FP103 L1 Output filter inductor Chip inductor 47uH/590mA C1 Output filter capacitor Tantalum capacitor 47uF/16V C2 Bypass capacitor Tantalum capacitor 10uF/25V R SE Current sense resistor Chip resistor 0.1 Ω RLED1 ~ RLED6 *2 LED current ballast resistor Chip resistor , 1% 4.0 Ω RFB1a ~ RFB1f Buck converter feedback loop component Chip resistor 120 ㏀ (table 3) RFB2 *3 Buck converter feedback loop component Chip resistor , 1% 68 ㏀ (table 2) *1 : For cost down , it is possible to use discrete component with a PNP transistor and a schottky barrier diode. In this case, you make use the discrete components with proper electrical specification. Table A shows the required key electrical limits. It is recommended to use PNP and schottky barrier diode having equivalent specification in the Table A. *2, *3 : To setting appropriate LED current, Refer to ‘Application Hints’. Component Parameter Ratings Unit Remarks PNP Collector to Emitter Voltage -23 V Recommend ‘2SB1706’ by ROHM or Equivalent ICCollector Current -2 A Schottky Barrier Diode Repetitive Peak Reverse Voltage 30 V Recommend ‘RSX101M-30’ by ROHM or EquivalentAverage Rectified Current 700 mA Table A : Selection guide for the discrete components

Jun. 07. 2008 / Rev. 0.1 ADT7110 * This specifications are subject to be changed without notice http://www.ad-tech.co.kr Pin Configuration Pin No. Name I/O Type Description 1 RS I A Current sense and provide voltage feed-forward.

2 GND - G Ground

3 PWM O D Switching output.

4 FB I A Feedback voltage input

5 EN I D Device enable pin

6 VIN - P Power supply input

I : Input pin O : Output pin IO : Input/Output pin P : Power pin G : Ground pin A : Analog pin D : Digital pin A11 Functional Block Diagram Internal REG. BIAS REF EN GND FB VIN RS SW Current Sense - +OSC ∑ PWM Comparator Driver gm Control Logic Set Set Error Amplifier Current Limit

Jun. 07. 2008 / Rev. 0.1 ADT7110 * This specifications are subject to be changed without notice http://www.ad-tech.co.kr Absolute Maximum Ratings Note1. derate 301℃/W above +70℃. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Parameter Symbol Min. Typ. Max. Unit Power supply voltage V IN -- 2 3 V Power dissipation (Ta=70℃) (Note1) P Dmax -- 2 6 5 ㎽ Storage temperature T STG -65 - +150 ℃ Junction temperature T Jmax -- + 1 5 0 ℃ Thermal resistance ΘJA -3 0 1 . 2- ℃/W Operating Ratings Parameter Symbol Min. Typ. Max. Unit Power supply voltage*2 VIN 10.5 12.0 15.0 V Operating temperature T OPR -20 - +85 ℃ Junction temperature T J -- + 1 2 5 ℃ Max. power dissipation (Ta=70℃)*1 PD -- 1 8 0 ㎽ *1 This spec. indicates that junction temperature of the device is under 125℃. In specific applications , this is recommended under this power dissipation specification. *2 Minimum VIN operating range is dependant to the VOUT voltage. ( VIN min. ≒ VOUT + 0.5V) Maximum VIN operating range can be extended. In this case, maximum drive current is limited. For using VIN over 15V, refer to the Table B. Electrical Characteristics (Ta=25℃, VIN=12V, unless otherwise noted) Parameter Condition MIN TYP MAX Unit Note Supply current, operating V(EN) = 3.3V , IO=300㎃ - 6 9 ㎃ Supply current, disable V(EN) = 0V - 90 200 ㎂ V(EN), input voltage high - 2.4 - - V V(EN), input voltage low - - - 1.2 V PWM controller Output drive current VIN ≤ 15V - 300 350 ㎃ Current limit - 550 - - ㎃ Efficiency IO=300㎃ - 85 - % Oscillator frequency IO=300㎃ 350 500 625 ㎑ Feedback voltage (VFB) IO=300㎃ 2.16 2.21 2.26 V VIN ( V ) 1 61 71 81 92 02 12 2 Drive current (㎃) 330 310 290 270 250 230 210 Table B : Maximum drive current as maximum VIN operating voltage.

Jun. 07. 2008 / Rev. 0.1 ADT7110 * This specifications are subject to be changed without notice http://www.ad-tech.co.kr Typical Performance Characteristics LED current vs. Ta Switching frequency vs. Ta Efficiency vs. Load current 30 40 50 60 70 80 90 Ambient temperature (℃) LED current (mA) 490 495 500 505 510 30 40 50 60 70 80 90 Ambient temperature (℃) Freq (kHz) 75% 80% 85% 90% 100 150 200 250 300 350 400 Load current (mA) Efficiency (%) VIN=12V VIN=15V

Jun. 07. 2008 / Rev. 0.1 ADT7110 * This specifications are subject to be changed without notice http://www.ad-tech.co.kr iii) Choose the RFB1 (= RFB1a ~ RFB1f ) RFB1 is used to biasing of LED. And these resistor value should be changed by the number of the LED branch. Therefore you should choose appropriate R FB1 value according to the LED branch count. The R FB1 selection formula is shown as below. Typical application circuit shows 6 LED branches and each LED branch has 6 series LEDs. In this circuit, proper R FB1 value is 120㏀and RFB1a ~ RFB1f value are used 120㏀ equally. The RFB1 value by the number of LED branch is shown below. < table 3 > RFB1 by the LED branches ▶LED current check The accurate method of measuri ng LED current is to measure the voltage on current ballast resistor (R LED). And then the LED current is simply obtained by dividing this voltage by R LED. To measure voltage on R LED accurately, (-) probe of the voltage meter is connected to (-) terminal of the ballast resistor and measure the voltage of (+) terminal on ballast resistor. Fig. 2 shows the method of measuring voltage on ballast resistor. It is possible to calculate the LED current by measuring of ICC current. As the ADT7110 is basica lly buck converter, its ICC current is the function of VIN, VOUT, LED branch current and quiescent current. Therefore it is not easy to calculate accurate LED current by measurement of ICC current. The relation LED branch current to the ICC current is shown below formula. Application Hints ▶LED Current control The LED current is determined by current ballast resistor (RLED1~RLED6) and feedback resistor (R FB2). The current setting procedure is described as below. i) Choose the RLED1 ~ RLED6 The voltage on current ballast resistor (R LED) is about 200mV normally. So the LED current is 200mV/RLED. In order to set LED current accurately, the precision resistors are preferred (1% recommended). The RLED value as LED current is shown as below table. < table 1 > RLED vs. LED current ii) Choose the RFB2 Secondly you choose appropriate R FB2 value for setting VLED. RFB2 is determined by forward voltage of the 6 series LEDs because the forward voltages of LED are different each other according to the LED manufacturers. (1.2 ~ 1.5volts for V F setting current flow away). The table and formula of the RFB2 are shown as below. < table 2 > RFB2 vs. VLED Where the VLED is the sum of the forward voltage in 6 series LEDs at setting current and V FB is the feedback voltage. (typically 2.21V) Fig. 1 shows the method of measuring VLED. RLED (Ω) LED current (mA) 5.76 35 4.42 45 4.02 50 2.67 75 2.49 80 100uA VVLEDR FB FB −≈2 VLED Setting current RFB2 (kΩ) VLED (V) 61.9 8.4 64.9 8.6 66.5 8.8 68.1 9.0 69.8 9.2 71.5 9.4 73.2 9.6 75.0 9.8 <Fig. 1 VLED test> branchesLEDofnumberkRFB1 ×Ω≈ 20 Number of LED branch R FB1 (kΩ) 6 120 5 100 48 0 36 0 24 0 12 0 RLED1 Voltage meter (+) (-) LED current= V(RLED1)/RLED1 V(RLED1) <Fig. 2 LED current test> conditionappliedatADT7110theofefficiencyefficiency branchLEDofnumbertheN whereN V VefficiencyICCI OUT IN branch1LED ,. ×××≈

Jun. 07. 2008 / Rev. 0.1 ADT7110 * This specifications are subject to be changed without notice http://www.ad-tech.co.kr Application Hints (continued) Example : typical application circuit N = 6 (6 LED branches) V IN = 12V , VOUT = 9V ICC = 280mA (measured) , and efficiency is 80%. So, calculated 1 branch LED current is 49.77mA. ▶Dimming control The LED brightness control can be obtained by forcing a pulse wave to the EN input terminal. Typically, a 100Hz to 1kHz pulse signal is used. LED brightness is proportional to the duty of pulse wave. And in this case , LED branch current is RMS value of the PWM modulated current. When the pulse-width is below 50% duty, the driving current of ADT7110 can be increased up to current limit condition.(~550mA) But you keep carefully to select the inductor (L1) over 700mA rated current. Note that the inductor (L1) is 590mA rated in typical application circuit.

Jun. 07. 2008 / Rev. 0.1 ADT7110 * This specifications are subject to be changed without notice http://www.ad-tech.co.kr Package ; SOT-26, 2.9mm x 1.6mm body (units : mm)