BIT3368

BIT3368 BIT3368 High Performance PWM Controller Version: A02 Revision No. Date Page A01 2014-10-08 1--9 A02 2015-07-30 7 Description Formal Specification was first issued. Add OCP Current-Sense (CS) Voltage = 0.3V Please read the notice stated in this preamble carefully before accessing any contents of the document attached. Admission of BiTEK’s statement therein is presumed once the document is released to the receiver. BIT3368 Notice: Firstly, the information furnished by Beyond Innovation Technology Co. Ltd. (BiTEK) in this document is believed to be accurate and reliable and subject to BiTEK’s amendment without prior notice. And the aforesaid information does not form any part or parts of any quotation or contract between BiTEK and the information receiver. Further, no responsibility is assumed for the usage of the aforesaid information. BiTEK makes no representation that the interconnect of its circuits as described herein will not infringe on exiting or future patent rights, nor do the descriptions contained herein imply the granting of licenses to make, use or sell equipment constructed in accordance therewith. Besides, the product in this document is not designed for use in life support appliances, devices, or systems where malfunction of this product can reasonably be expected to result in personal injury. BiTEK customers’ using or selling this product for use in such applications shall do so at their own risk and agree to fully indemnify BiTEK for any damage resulting from such improper use or sale. At last, the information furnished in this document is the property of BiTEK and shall be treated as highly confidentiality; any kind of distribution, disclosure, copying, transformation or use of whole or parts of this document without duly authorization from BiTEK by prior written consent is strictly prohibited. The receiver shall fully compensate BiTEK without any reservation for any losses thereof due to its violation of BiTEK’s confidential request. The receiver is deemed to agree on BiTEK’s confidential request therein suppose that said receiver receives this document without making any expressly opposition. In the condition that aforesaid opposition is made, the receiver shall return this document to BiTEK immediately without any delay. BIT3368 Features: Pin Layout:
Current mode control and fixed frequency operation
8V ~ 18V operation voltage
Internal minimum off time
Internal soft-start
Over voltage protection, OVP
Load short protection, LSP
Schottky short protection, SSP
Schottky open protection
LED cathode short protection, LCSP
Over temperature protection, OTP
Inductor short protection
Internal under voltage lock out, UVLO
Totem pole output
SOP-8 package 1 2 3 4 General Description: CMP OUT INN OCP EA GND VDD OVP 8 7 6 5 Recommended Operating Condition: The BIT3368 is a DC-DC converter with Current-Mode control and three optional operation PWM frequencies. Low 0.21V feedback voltage, Over Voltage Protection, Over Current Protection, Schottky diode open/short protection and inductor-shorted protection make BIT3368O to be an ideal controller for LED backlight driver. Internal soft start function can avoid inrush current happened in the start-up period. Additional Over-Temperature-Protection and UVLO make system more reliable. CMOS process greatly reduces the operating current when comparing to similar products. Supply voltage……………………….8V ~ 18V Operating frequency………….…….55kHz/110kHz/220kHz Operating ambient temperature…...-20 ~ 85 ℃ ℃ Absolute ratings VDD…………………………...…………-0.3 ~ +18 V GND…………………..………….………±0.3 V Input voltage……………….…….……..-0.3 ~ VDD+0.3 V Operating ambient temperature……...-20 ~ 85 Operating junction temperature…..….+150 Storage temperature……………..…….-55~ 150 ℃ Functional block diagram: EA 100mV + 2.1V + - OVP OTP Dimming control EA UVLO VDD LSP protection CMP INN 0.21V + EA + 3.5V + - Soft start PWM comparator Leading edge blanking Σ Frequency selection OCP 1V OSC + OCP comparator Internal bias & Reference delay delay Digital control circuit Buffer OUT ℃ ℃ BIT3368 Pin description: Pin No. Symbol Descriptions 1 CMP Output of the error amplifier 2 INN The inverting input of the error amplifier 3 EA Enable and dimming input 4 VDD Power supply 5 OVP Over voltage protection 6 GND Ground pin 7 OCP Over current protection 8 OUT Output pin Functional Description: Under Voltage Locked Out, UVLO: To avoid the abnormal condition happened when the input voltage drops to low voltage, it is needed to set a low voltage Current mode control and slope compensation operation point. Please refer following figure, when the input For the Boost converter operation, peak current mode controls voltage is below the low voltage operation point, the under power switch according inductor current. It detects the rising voltage lockout (UVLO) function will turn-off its output and inductor current and turns off power switch when the inductor most of its internal functions. The recovery hysteresis voltage current reaches the control level. In addition, BIT3368 built-in is about 1V. slope compensation is used to avoid sub-harmonic oscillation when the duty cycle is larger than 50% for the peak current operation. Some advantages of current mode control is fast UVLO response on line and load regulation, it is also easily been hysteresis compensated for stability requirement. t Control point Frequency selection In the initial state, BIT3368 frequency can be selectable by an t external resistor connected in OCP pin. Please refer R1 as Switch current following figure and selection table for frequency selection. t Switch control signal 1 2 3 4 CMP OUT INN OCP EA GND VDD OVP 8 Resistor frequency 10k ohm 55kHz Leading edge blanking and current limit 1k ohm 110kHz For the turn on of power switch, please refer following figure, 22k ohm 220kHz the current spike will be happened in the rising edge. The 7 6 5 R1 leading edge blanking (LEB) time was built-in the pin of OCP BIT3368 to prevent the false-trigger from the current spike. In addition, BIT3368 limits the maximum current flowing through the LED current regulation and DC dimming external MOSFET. To stabilize the LED current, BIT3368 senses LED current and adjust PWM duty cycle for the purpose. The average LED current is approximated by following equation, Switch control signal ILED = LEB time 0.21 Rs Switch current Where, 0.21V is BIT3368 internal reference voltage. In addition, the DC dimming can also been applied in this feedback loop. Please check following figure for detailed. Soft start To avoid inrush current happened in the start-up period, the soft-start circuit is needed. It can reduce current overshoot 0.21V happened in the start-up period and used components suffer less over stress and better lifecycle. BIT3368 with long INN DC signal PWM signal R1 + R2 soft-start time makes system reliable and can be used in many RS different applications. PWM dimming and EA control For the LED backlight application, the dimming function is The LED current is controlled as negative dimming, and LED needed to adjust backlight brightness. Normally, it is directly to current is approximated by following equation, control LED current for kinds of brightness. BIT3368 can accept PWM signal for the function of PWM positive dimming. Following figure shows PWM dimming signal vs. LED current. 0.21 − ILED = R2 (DC − 0.21) R1 Rs For the negative PWM dimming, following figure shows PWM t dimming signal vs. LED current. LED current t PWM dimming signal t The LED dimming function is controlled by the PWM signal at LED current EA pin. This EA can accept an external PWM signal in the range of 100Hz to 1kHz with the level of 0V and higher than t PWM dimming signal 2.5V and 1%~100% dimming range. BIT3368 Over voltage protection, OVP: LED cathode short protection, LCSP When LED is fault or open status, the feedback loop of LED One LED fault condition is its cathode short to ground. This current is open and result the maximum duty happened. This fault condition will cause no feedback signal and maximum maximum duty cycle will cause the output voltage to a very duty. When maximum duty is happened and delay in a high level of the converter output. BIT3368 monitors this high moment, BIT3368 will latch-off its output. voltage level in its OVP pin and latch-off its output. It can be Schottky short protection released from VDD or EA. Normally, BIT3368 is operated in boost converter usually constructed by inductor, power switch and Schottky diode. R1 Schottky diode short is one fault condition to cause a large VFB OVP R2 OCP pin detects this large current and confirm this fault + - 2.1V current flowed from output capacitor to power MOS. When condition in a delay time, BIT3368 will latch-off its output. Schottky open protection The OVP voltage is as following In the boost converter operation, Schottky diode open is one fault condition to cause no feedback signal. When Schottky diode is opened, there will be maximum duty and abnormal Load short protection, LSP current in its input and power MOS. When some of a series LED are short suddenly, LSP function When Schottky diode is opened, there will be no output will be enabled to latch-off its output immediately. Please refer voltage been detected in the OVP pin of BIT3368. OVP pin following figure, the INN pin monitors LED current for feedback receives a very low voltage and confirm this fault condition in a regulation and LSP function. When all the LEDs are connected delay time, BIT3368 will latch-off its output. in series but some of them are short suddenly, this fault condition will cause a higher voltage signal in INN pin. When Inductor short protection INN pin detects a high voltage in this pin, BIT3368 will latch-off In the boost converter operation, inductor short is one fault its output. condition to cause large current in the input and power MOS. When OCP pin detects this large current and confirm this fault condition in a delay time, BIT3368 will latch-off its output. Over Temperature Protection, OTP BIT3368 provides over temperature protection that is more VFB INN 0.21V 1V + - CMP reliable for system protection. When the operation temperature is too high, BIT3368 will shut off its output. When + - the temperature drops below the threshold, BIT3368 will LSP protection automatically recover to work again. BIT3368 DC/AC Characteristics: TA=25℃ unless otherwise specified. Parameter Test Conditions Min. Typ. Max. Unit 18 V Supply voltages Pin VDD input 8 Under voltage look out Positive Going Threshold Hysteresis Chip consumed current 6 7 8 V 0.5 1 1.5 V 1 2 4 mA Enable control ON 2 VDD V OFF 0 0.8 V Error amplifier reference voltage Non-Inverting input of the error amplifier 0.203 0.21 0.217 V VDD=12V, Rosc=1kHz 99 110 121 KHz VDD=12V, Rosc=10kHz 49.5 55 60.5 kHz VDD=12V, Rosc=22kHz 198 220 242 kHz 1,000 Hz 90 dB Operating frequency and DIM frequency Operating frequency DIM frequency 100 Error amplifier Open loop gain Note1 50 70 Over current protection, OCP and over voltage protection, OVP OCP Current-Sense (CS) Voltage 0.3 V OCP Shutdown Protection Voltage 1 V OVP voltage 1.89 2.1 2.31 V 0.8 1 1.2 V Load short protection, LSP LSP voltage Over temperature protection, OTP Over temperature protection, OTP Note 1 180 hysteresis Note 1. 50 ℃ ℃ Note 1 30 ms Soft start and minimum output off time Soft start time Minimum off time 300 450 600 ns VDD V Output drive OUT voltage VDD=10V ~ 18V Rising Time VDD=12, 1000pF load Note1 Falling Time 0 30 ns 25 ns Note 1. Only guaranteed by simulation or sampled evaluation during –20~+85°C. Not 100% tested. BIT3368 Soldering information Reflow soldering: The choice of heating method may be influenced by plastic QFP package). If infrared or vapor phase heating is used and the package is not absolutely dry (less than 0.1% moisture content by weight), vaporization of the small amount of moisture in them can cause cracking of the plastic body. Preheating is necessary to dry the paste and evaporate the binding agent. Preheating duration: 45 minutes at 45 °C. Reflow soldering requires solder paste (a suspension of fine solder particles, flux and binding agent) to be applied to the printed-circuit board by screen printing, stenciling or pressure-syringe dispensing before package placement. Several methods exist for reflowing; for example, convection or convection/infrared heating in a conveyor type oven. Throughput times (preheating, soldering and cooling) vary between 100 and 200 seconds depending on heating method. Typical reflow peak temperatures range from 215 to 270 °C depending on solder paste material. The top-surface temperature of the packages should preferable be kept below 245 °C for thick/large packages (packages with a thickness 3 2.5 mm or with a volume 350 mm so called thick/large packages). The top-surface temperature of the packages should preferable be kept below 260 °C for thin/small packages (packages with a thickness < 2.5 mm and a volume < 350 3 mm so called thin/small packages). ≧ ≧ Stage 1’st Ram Up Rate Preheat 2’nd Ram Up Solder Joint Peak Temp Ram Down rate Condition max3.0+/-2 /sec 150 ~200 max3.0+/-2 /sec 217 above 260 +0/-5 6 /sec max ℃ ℃ ℃ ℃ ℃ ℃ ℃ Duration 60~180 sec 60~150 sec 20~40 sec - ℃ Temp ( ) 260 217 200 150 25 RT 60~ 180 60~150 Time(sec) Wave soldering: Conventional single wave soldering is not recommended for surface mount devices (SMDs) or printed-circuit boards with a high component density, as solder bridging and non-wetting can present major problems. Manual soldering: Fix the component by first soldering two diagonally-opposite end leads. Use a low voltage (24 V or less) soldering iron applied to the flat part of the lead. Contact time must be limited to 10 seconds at up to 300 °C. When using a dedicated tool, all other leads can be soldered in one operation within 2 to 5 seconds between 270 and 320 °C. BIT3368 Order information: BIT3368-SO SO: SOP Part number Beyond Innovation Technology Co., Ltd. Package information : Unit: mm SOP type :