TA848 Novel Low Cost Green-Power PWM Controller Features z z z z z z z z z Low Cost, PWM&PFM&CRM Low Start-up Current (about 10µA) Low Operating Current (about 2mA) Current Mode Operation Under Voltage Lockout (UVLO) Built-in Synchronized Slope Compensation Programmable PWM Frequency Leading edge Blanking on Sense input Constant output power limiting for z z z z universal AC input Cycle-by-cycle current limiting Clamped gate output voltage 16.5V Over voltage protect 26.7V High-Voltage CMOS Process with ESD z SOT-23-6L、SOP-8 & DIP-8 Pb-Free z Packaging Compatible with SG5701 & SG5848 & LD7535 &OB22632/63 z z Open Frame Switching Power Supply 384X Replacement Applications z z Switching AC/DC Adaptor Battery Charger General Description The TA848 is a highly integrated low cost current mode PWM controller, which is ideal for small power current mode of offline AC-DC fly-back converter applications. Making use of external resistors, the IC changes the operating frequency and automatically enters the PFM/CRM under light-load/zero-load conditions. This can minimize standby power consumption and achieve green-power functions. With a very low start-up current, the TA848 could use a large value start-up resistor (1.5Mohm). Built-in synchronized slope compensation enhances the stability of the system and avoids sub-harmonic oscillation. Dynamic peak limiting circuit minimizes output power change caused by delay time of the system over a universal AC input range. Leading Dec, 2006 V1.5 edge blanking circuit on current sense input could remove the signal glitch due to snubber circuit diode reverse recovery and thus greatly reduces the external component count and system cost in the design. Pulse-by-pulse current limiting ensures safe operation even during short-circuit. The TA848 offers more protection like OVP (Over Voltage Protection) and OCP (Over current protection). The CR6848’s output driver is clamped to maximum 16.5V to protect the power MOSFET. Excellent EMI performance is achieved soft switching control at the totem pole gate driver output. TA848 is offered in SOT-23-6, SOP-8 and DIP-8 packages. 1/14 TA848 TA8XX Series Part Number PWM Frequency Package TA848 External Adjustable DIP-8、SOP8 SOT-23-6L TA850 External Adjustable DIP-8、SOP8 SOT-23-6L TA851 External Adjustable DIP-8、SOP8 SOT-23-6L Description PWM&PFM&CRM 、 Current Mode 、 Slope Compensation Leading-edge Blanking 、 Gate Clamped、Over-voltage Protection、Over-current Protection、 Soft Drive. With All Functions of TA848 、 Gate soft Clamped With All Functions of TA850 、Frequency jitter、 Soft start、Sense Fault Protect、OLP、SCP、 OTP TYPICAL APPLICATION TA848 Dec, 2006 V1.5 2/14 TA848 Pin Assignment TA848S TA848T TA848S Pin Descriptions Name GND FB SEN Description GND Pin Analog Input. Voltage feedback pin (same as the COMP pin in UC384X), This pin is to program the switching frequency. By connecting a resistor to ground to set the switching frequency. Current sense pin, connect to sense the MOSFET current. VDD GATE Supply voltage pin. Gate output to drive the external power MOSFET. RI Block Diagram Simplified Internal Circuit Architecture Dec, 2006 V1.5 3/14 TA848 Absolute Maximum Ratings Symbol VDD IOVP VFB VSEN PD Parameter Supply voltage Pin Voltage VDD OVP maximal enter current Input Voltage to FB Pin Input Voltage to SEN Pin Power Dissipation ESD Capability, HBM Model ESD Capability, Machine Model 20 second Lead Temperature SOT-23-6L (Soldering) 10 second DIP-8 Storage Temperature Range TL TSTG Rating 40 20 -0.3 to 6V -0.3 to 6V 300 2000 200 Unit V mA V V mW V V 220 ℃ 260 ℃ -55 to + 150 ℃ RECOMMENDED OPERATION CONDITION Symbol VDD VDD Supply Voltage Min ~ Max Unit 11~20 V RI RI PIN Resistor Value 58~120 K ohm TOA Operation Ambient Temperature -20~85 ℃ PO Output Power 0~60 W 48~100 kHz FPWM Dec, 2006 Parameter V1.5 Frequency of PWM 4/14 TA848 Electrical Characteristics (Ta=25°C unless otherwise noted, VDD = 15V.) Symbol Parameter Conditions Min. Typ. Max. Unit Supply Voltage (VDD Pin) IST ISS Startup Current Operating Current 10 µA VFB=0V 2.8 mA VFB=3V 2.3 mA VFB=Open 1.46 mA VDDON Turn-on Threshold Voltage 16.1 V VDDOFF Turn-off Threshold Voltage 11.1 V VDCLAMP VDD Clamp Voltage IVDD=20mA 26.7 V Voltage Feedback (FB Pin) IFB Short Circuit Current VFB=0V 2.8 mA VFB Open Loop Voltage VFB=Open 4.8 V IPFM Enter PFM, FB current 0.92 mA ICRM Enter CRM, FB current 1.5 mA 0.87 V Current Sensing (SEN Pin) VTH_L Minimum Voltage Lever 0.83 VTH_H Maximum Voltage Lever 1.0 TPD Delay to Output 300 ns RCS Input Impedance 50 KΩ 1.05 V Oscillator (RI Pin) FOSC Normal Frequency RI=100Kohm FPFM PFM Frequency RI=100Kohm 11.6 KHZ DCMAX Maximum Duty Cycle RI=100Kohm 75 % ΔFTEMP Frequency Temp. Stability -30-85℃ 5 % 300 nS TBLANK 53 Leading-Edge Blanking Time 58 63 KHz GATE Drive Output (GATE Pin) VOL Output Low Level VDD=15V, IO=20mA VOH Output High Level VDD=15V, IO=20mA TR Rising Time CL=1000pF 450 ns TF Falling Time CL=1000pF 130 ns Output Clamp Voltage VDD=20V 16.5 V VGCLAMP Dec, 2006 V1.5 1 8 V V 5/14 TA848 TYPICAL CHARACTERISTICS VDD startup Current VS Temperature VDD startup Current VS Temperature VDD (OFF) VS Temperature VDD Operation Current VS Temperature OVP VS Temperature PWM frequency VS Temperature Duty cycle VS Temperature FOSC VS FB Current Dec, 2006 V1.5 6/14 TA848 FOSC VS RI pin resistor Dec, 2006 V1.5 7/14 TA848 OPERATION DESCRIPTION Current Model Compared to voltage model control, current model control has a current feedback loop. When the voltage of the sense resistor peak current of the primary winding reaches the internal setting value VTH, comparator reverse, register reset and power MOSFET cut-off. So that to detect and modulate the peak current cycle by cycle could control the output of the power supply. The current feedback has a good linear modulation rate and a fast input and output dynamic impact avoid the pole that the output filter inductance brings and the second class system descends to first class and so it widens the frequency range and optimizes overload protection and short circuit protection. Startup Current and Under Voltage Lockout The startup current of TA848 is set to be very low so that a large value startup resistor can therefore be used to minimize the power loss. For AC to DC adaptor with universal input range design, a 1.5 MΩ, 1/8 W startup resistor and a 10uF/25V VDD hold capacitor could be used. The turn-on and turn-off threshold of the TA848 is designed to 16.1V/11.1V. During startup, the hold-up capacitor must be charge to 16.1V through the startup resistor. The hysteresis is implemented to prevent the shutdown from the voltage dip during startup. Internal Bias and OSC Operation A resistor connected between RI pin and GND pin set the internal constant current source to charge or discharge the internal fixed cap. The charge time and discharge time determine the internal clock speed and the switching frequency. Increasing the resistance will reduce the value of the input current and reduce the switching frequency. The relationship between RI pin and PWM switching frequency follows the below equation within the RI allowed range. FOSC = Green Power Operation The power dissipation of switching mode power supply is very important in zero load or light load condition. The major dissipation result from conduction loss、switching loss and consume of the control circuit. However, all of them related to the switching frequency. There are many difference topologies has been implemented in different chip. The basic operation theory of all these approaches intended to reduce the switching frequency under light-load or no-load condition. TA848`s green power function adapts PWM、PFM and CRM combining modulation. When RI resistor is 100k, the PWM frequency is 58kHz in medium or heavy load operation. Through modifying the pulse width, TA848 could control output voltage. The current of FB pin increases when the load is in light condition and the internal mode controller enters PFM&PWM when the feedback current is over 0.92mA. The operation frequency of oscillator is to descend gradually. The invariable frequency of oscillator is 11.6kHz when the feedback current is over 1.05mA. To decrease the standby consumption of the power supply , Chip-Rail introduces the Cycle Reset Mode technology；If the feedback current were over 1.1mA, mode controller of TA848 would reset internal register all the time and cut off the gate pin, while the output voltage is lower than the set value, it would set register, gate pin operating again. Although the frequency of the internal OSC is invariable, the register would reset some pulses so that the practical frequency is decreased at the gate pin. 5800 (kHz ) RI ( KΩ) For example, a 100kΩ resistor RI could generate a 50uA constant current and a 58kHz PWM switching frequency. The Dec, 2006 suggested operating frequency range of TA848 is within 48KHz to 100KHz. V1.5 TA848 Green-Power Function 8/14 TA848 Internal Synchronized Compensation Slop Although there are more advantages of the current mode control than conventional voltage mode control, there are still several drawbacks of peak-sensing current-mode converter. Especially the open loop instability when it operates in higher than 50% of the duty-cycle. TA848 is introduced an internal slope compensation adding voltage ramp to the current sense input voltage for PWM generation to solve this problem. It improves the close loop stability greatly at CCM, prevents the sub-harmonic oscillation and thus reduces the output ripple voltage. VSLOP = 0.33 × DUTY = 0.4389 × DUTY DUTYMAX primary wind inductance. V IN ranges from 85VAC to 264VAC. To guarantee the output power is a constant for universal input AC voltage, there is a dynamic peak limit circuit to compensate the system delay T that the system delay brings on. Leading-edge Blanking (LEB) Each time the power MOSFET is switched on, a turn-on spike will inevitably occur at the sense pin, which would disturb the internal signal from the sampling of the RSENSE. There is a 300n sec leading edge blanking time built in to avoid the effect of the turn-on spike and the power MOSFET cannot be switched off during this time. So that the conventional external RC filtering on sense input is no longer required. TA848 Current Sensing & Dynamic peak limiting The current flowing by the power MOSFET comes in to being a voltage VSENSE on the sense pin cycle by cycle, which compares to the internal reference voltage, controls the reverse of the internal register, limits the peak current IMAX of the primary of the transformer. The energy E = 1 2 × L × I MAX 2 deposited by the transformer. So adjusting the RSENSE can set the Max output power of the power supple mode. The current flowing by the power MOSFET has an extra value ∆I = V IN × TD due to the system delay T LP that the current detected from the sense pin to power MOSFET cut off in the TA848 (Among these, VIN is the primary winding voltage of the transformer and LP is the Dec, 2006 V1.5 Over Voltage Protection (OVP) There is a 26.7V over-voltage protection circuit in the CR6848 to improve the credibility and extend the life of the chip. The GATE is to shutdown immediately when the voltage of the VDD is over 26.7V and the voltage of VDD is to descend rapidly. Gate Driver & Soft Clamped TA848’ output designs a totem pole to drive a periphery power MOSFET. The dead time is introduced to minimize the transfixion current when the output is drove. The NMOS is shut off when the other NMOS is turned on. The clamp technology is introduced to protect the periphery power MOSFET from breaking down. 9/14 TA848 PACKAGE DEMENSIONS DIP-8L Dimensions Symbol Millimeters Min. Typ. A Max. Min. Typ. 5.334 A1 0.381 A2 3.175 0.210 3.302 3.429 0.125 0.130 b 1.524 0.060 0.457 0.018 9.017 E E1 9.271 10.160 0.355 7.620 6.223 6.350 L 2.921 eB θ˚ 0.365 0.135 0.400 0.300 6.477 0.245 0.250 3.302 3.810 0.115 0.130 0.150 8.509 9.017 9.525 0.335 0.355 0.375 0˚ 7˚ 15˚ 0˚ 7˚ 15˚ e V1.5 Max. 0.015 b1 D Dec, 2006 Inches 2.540 0.255 0.100 10/14 TA848 SOT-23-6L Symbol Dec, 2006 V1.5 Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.700 1.000 0.028 0.039 A1 0.000 0.100 0.000 0.004 B 1.397 1.803 0.055 0.071 b 0.300 0.559 0.012 0.022 C 2.591 3.000 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 11/14 TA848 SOP-8L Dimensions DISCLAIMERS Symbol Min. A 1.346 A1 0.101 b Min. 1.752 0.053 0.254 0.004 E 3.810 e 1.016 Max. 0.069 0.010 0.008 4.978 1.270 0.381X45 ° Inch Typ. 0.016 0.203 4.648 F Dec, 2006 Max. 0.406 c D Millimeter Typ. 0.183 3.987 0.150 1.524 0.040 0.196 0.157 0.050 0.015X45 ° 0.060 H 5.791 6.197 0.228 0.244 L 0.406 1.270 0.016 0.050 θ˚ 0° 8° 0° 8° V1.5 12/14 TA848 REFERENCE CIRCUIT 1 TA848 drives a periphery Power MOSFET. 5V/6A 30W Power Supply Quantity 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1 Part Number C1 C2 C3 C4 C5 C7 C8 C6、C7 C8 BD1 D1 D2 D3 D4 T1 T2 Description Quantity 102/1000V 103/1000V 104 33uF/400V 223/1000V 103/1000V 102/100V 1 1 1 2 1 1 1 1 1000 uF/25V 104 KBL406 FR107 1N4007 Y2010D LED 20mH EI-22 1 1 2 1 1 1 1 Part Number Description F1 L1 R1 R2、R3 R4 R5 R6 0.25A 10uH 20R 1K 100K 100K/0.5W 47R R7 R8 R9 R11、R12 U1 U2 U3 Q1 1.5M 0R51 20R 3.3K TA848 PC817 TL431 2N60 Notice: Q1 is a Power MOSFET Dec, 2006 V1.5 13/14 TA848 REFERENCE CIRCUIT 2 TA848 drives a periphery Power BJT （5V/3A 15W Power Supply） Quantity 2 1 1 1 1 1 1 1 2 1 5 2 1 1 2 1 1 1 Part Number Description Quantity C1、C2 C3 C4 C5 C6 C7 C8 104/400V 472 102 33uF/400V 10uF/50V 103/1000V 102/100V C9 C10、C11 C12 D1、D2、D3、 D4、D5 D6、D7 D8 D9 D10、D11 T1 T2 F1 223/1000V 220uF/16V 1.0uF/16V 1N4007 1N4148 18V SB560 FR107 20mH EI-22 0.25A Part Number Description 1 1 1 1 2 1 1 2 R2 R3 R4 R5 R6、R7 R8 R9 100K 100K/0.5W 1K 1.5M 220R/1W 220R 20K 1 1 R12 R13 20R 1R2/1W 20K 1 1 1 1 1 1 1 R14 U1 U2 U3 U4 Q1 Q2 2K2 TA848 PC817 TL431 LM358 13003 9013 R10、R11 Notice: Q1 is a Power BJT Dec, 2006 V1.5 14/14