C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications ADVANTAGES Low system component count High average efficiency Low standby power consumption EMI compliance without extra components High isolation & surge voltage withstand High power density in very small size C2474PW1 PDIP-8 FEATURES Highly integrated CMOS controller IC Low cost package options Drive suitable for low cost bipolar power transistors Resonant switching for high efficiency and low EMI Frequency optimised for power circuit parasitics Protection against overload, over-temperature and under-voltage C2472PX2 SOT23-6 C2473PX1 SOP-8 APPLICATIONS External AC/DC charger/adaptor (single voltage input) e.g. cordless phones, portable electric tools. Embedded PSU (single voltage input) e.g. set-top boxes, DVD players, audio products, domestic appliances. OVERVIEW The C2472, C2473 and C2474 controllers use CamSemi’s Resonant Discontinuous Forward Converter (RDFC) topology to create a high efficiency, low cost alternative to line-frequency transformer PSUs. By operating in resonant mode, EMI is greatly reduced, enabling the replacement of linear PSUs in demanding applications such as audio products and cordless phone chargers. The C2472, C2473 and C2474 controllers also offer overload protection which is usually associated with more expensive switch mode solutions. AUX VDD Vdd Switch saturation sensing Vdd regulator Base drive COL Resonance sensing CS Current sensing RDFC Control BAS GND Figure 1: Block Diagram of the C2472, C2473 and C2474 Controller ICs Product data © Cambridge Semiconductor Ltd 2007 Page 1 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications PIN DEFINITIONS Figure 2: C2472, C2473 and C2474 Pin Assignment (drawings are not to scale) VDD Pin The VDD pin supplies power to the controller and is maintained at the correct voltage (nominally 3.3 V) by an internal shunt regulator. COL Pin The COL pin is used to sense the collector voltage of the primary switching transistor, via a c oupling capacitor, to control the timing and current levels of the signals produced on the BAS pin. CS Pin The CS pin senses the primary switch current via the current sensing resistor. The voltage sensed on this pin is used to control the operating modes to manage standby and overload protection. Operating characteristics are programmed via two external resistors. AUX Pin The AUX pin provides the supply current for the internal base driver block. In most applications, the AUX pin is connected to the external supply rail via an NPN transistor and a current-limiting resistor to set the maximum base current; however, in low power applications the AUX pin can be connected to the VDD pin via the limiting resistor, with some compromise on the standby power consumption. BAS Pin The BAS pin switches the external bipolar primary switch transistor on and off. The current supplied to the switch transistor is controlled to minimize the switching losses and thereby help optimize overall system efficiency. GND Pin GND pins provide the ground reference. Where the device has multiple GND pins, all must be connected to a common, low impedance path. Product data © Cambridge Semiconductor Ltd 2007 Page 2 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications TYPICAL APPLICATION CIRCUIT The C2472, C2473 and C2474 controllers are intended primarily for single input voltage AC/DC applications, such as replacement of line frequency linear transformer power supplies. These versatile controllers support a wide range of applications at low cost. A typical circuit configuration is shown in Figure 3. Figure 3: Typical RDFC Application Schematic Typical 12 W Charger Performance Input 115 V ac Output 12 V, 1 A dc Efficiency > 80% No-load power input < 150 mW Typical Maximum Application Rated Power Power Switch (Q1) Gain 115 Vac 230 Vac Standard 20 W 40 W High 40 W 60 W Product data © Cambridge Semiconductor Ltd 2007 Page 3 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications PRINCIPLE OF OPERATION Power-Up/Power-Down Sequences The C2472, C2473 and C2474 controllers are powered via their VDD pins. When mains voltage is first applied, a small amount of current (I DDSLEEP) is drawn from the rectified mains input via high value start up resistors (Rht1 and Rht2 in Figure 3). When the voltage on the VDD pin (VDD) reaches a level V OVDTHR the controller wakes up, demands more supply current (I DDWAKE) and enters the Start-up state (see Figure 4). The controller stays in Start-up for a short time during which internal circuit blocks are enabled and then changes to Active operation. In both Start-up and Active states, the controller uses an internal shunt regulator to regulate the V DD rail voltage; the regulator is disabled in Sleep. A higher regulation voltage is applied during Start-up (VDDREG(S)) than during Active operation (VDDREG(R)) to help provide sufficient VDD before the Auxiliary supply from the transformer rises to maintain VDD . VDDREG(R) VDDREG(S) If the VDD pin voltage drops below V UVDTHR the controller goes back to Sleep, redu cing the supply current demand. The system will restart when input power is restored. To achieve a smooth power up sequence the VDD reservoir capacitor needs to be large enough to sustain the supply above V UVDTHR over the Start-up period. Figure 4: VDD Pin Waveform (VDD) During Initial Power-up and Power-down State Description Sleep From initial application of power or from Active state if VDD falls below VUVDTHR, the controller changes to Sleep state. Non-essential controller circuits are powered down and the external switching transistor (Q1) is held off. Exit from Sleep state occurs when VDD rises above VOVDTHR and the controller moves to the Start-up state. Start-up When the Start-up state is entered, internal controller circuits are activated and power conversion begins (Standby mode – see Table 2). In Start-up the on-chip shunt regulator stabilises VDD to an intermediate value, VDDREG(S). After a preset time, the controller changes from Start-up to Active operation. Active Converter operation continues, the shunt regulator controls VDD to the lower VDDREG(R). If VDD falls below VUVDTHR the controller ceases converter operation and reverts to Sleep state. Table 1: Summary of RDFC Controller States Product data © Cambridge Semiconductor Ltd 2007 Page 4 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications Start-up and Active State Power Conversion Modes In the Start-up and Active states the C2472, C2473 and C2474 ICs have several modes for controlling power conversion that are designed to achieve maximum efficiency and to limit power (current) across a wide range of loads. Refer to Table 2 for a summary of each mode. Mode Typical Load Range Description Standby IOUT ≥ 0% to ~20% of rated current Standby mode reduces power consumption at low loads. It achieves this by progressively reducing the on-time then by increasing the off-time as the load decreases. As load increases, the converter duty is increased until the controller returns to Normal mode. Typically, mains ripple causes change of operating mode during each mains half-cycle, with the converter moving to lower-power modes between peaks of the mains voltage. Normal IOUT > ~20% to 100% of rated current Normal mode is used for steady state power delivery. During Normal mode the power device switches in a fully resonant minimum-voltage-switching waveform, with the offtime determined by the transformer resonance (TRES) and the on-time being equal to 75% of the off time. A low level of primary switch current, sensed via the CS pin voltage, causes the controller to change to Standby mode and a high level to Overload mode. Overload IOUT >~100% rated current Overload mode is activated at high output loads. In this mode the on-time of the primary switch is terminated early (before 75% of TRES) when the primary current exceeds a preset maximum, thereby protecting the primary switch and limiting the output current. This results in reduction of the output voltage. Heavy overload (sensed by the on-period of the primary switch reducing below a preset time) causes Foldback mode to be entered. Foldback VOUT < ~70% rated output Foldback mode is entered from the Overload mode. In this mode the controller reduces the on/off duty cycle to protect the power supply and any connected load by both shortening the on-period and increasing the off-period of the primary switch. Converter cycles continue to maintain auxiliary power to the controller. The controller exits the Foldback mode and enters the Power Burst mode after a fixed number of power conversion cycles. Power Burst VOUT < ~70% rated output Power Burst mode is entered periodically from Foldback mode in order to restart the power supply output. In Power Burst mode, the controller operates at maximum delivered power for a set number of power converter cycles. At the end of the burst, if the load is not excessive, the converter goes to Normal mode; otherwise it reverts to Foldback mode. Table 2: Summary of Active Operating Modes When the controller goes from Sleep to Start-up state, its power conversion mode is set to Standby. Typically the converter output voltage is low at this time so the primary switch current is high during the first few converter cycles. This causes the operating mode to change quickly to Normal or Overload mode. Product data © Cambridge Semiconductor Ltd 2007 Page 5 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications RDFC Power Supply I-V Characteristic Figure 5 illustrates a typical RDFC power supply characteristic with the various Active state modes of operation identified. INOM and VNOM are the nominal output voltage and current drawn by the load at the rated power of the application circuit. Figure 5: Typical RDFC Power Supply Characteristic Indicating Different Active Modes of Operation The exact thresholds for transition between modes depend on specific application characteristics, controller internal clock frequency (FCLK) and CS pin thresholds (VOCPH and VOCPL). These parameters and their effects are explained later. Product data © Cambridge Semiconductor Ltd 2007 Page 6 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications Switching Waveforms Overload Standby Normal The collector voltage (VCE) and current (I C) waveforms of the primary switching transistor (Q1 in Figure 3) are shown in Figure 6. T RES is the duration of the transformer resonance during the off period. Note that in Overload mode, the primary switch Q1 is turned off when the current exceeds the protection level OCPH (sensed by the CS pin voltage). Figure 6: Typical Switch (Q1) Collector Voltage (V CE) and Current (IC) Waveforms Product data © Cambridge Semiconductor Ltd 2007 Page 7 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications Resonance Control The natural resonance of the transformer and associated components is deduced from the current flowing into and out of the COL pin via the collector coupling capacitor. The voltage sensed on the COL pin is used to control saturation of the primary switch transistor (Q1 in Figure 3) during the on-period (see “Optimised Base Drive”). During the off-period, timing of the resonance is detected via the current in and out of the pin , which has a low impedance path to GND during this time. Rate of change of voltage at the transformer primary causes current into or out of the COL pin, which is processed to measure the resonance period T RES and to find the optimum turn-on time for the following conversion cycle. The resonant period is also used to determine the maximum on -time of the primary switch transistor, so that T ON = 0.75 x T RES The maximum duty cycle (D NORMAL) is therefore nominally 43%. On-time of the switch is controlled to manage power delivery and is reduced in both low-load and overload conditions. The minimum on-time in overload is determined by the internal CS blanking, specified as T CSBLANK. At turn-on of the primary switching transistor, its collector voltage can fall very rapidly, with correspondingly large current out of or in to the COL pin via the coupling capacitor (Ccol). An on-chip clamp transistor, controlled by an internal signal called ACTICLAMP, provides a low resistance path to GND. This transistor is turned on shortly before turn-on of the primary switch and remains on until time T ACT after turn-on of the primary switch. It is then turned off during the remainder of the primary switch on-period. In some applications, the current through the coupling capacitor may develop sufficient voltage across the clamp transistor to cause conduction of the ESD protection diodes. This is permissible up to a limit ICOL which is specified in ABSOLUTE MAXIMUM RATINGS. If, due to application design, the capacitor current could exceed this level, external protection diodes and a resistor must be provided ( Dcol1, Dcol2 and Rcol in Figure 3). Product data © Cambridge Semiconductor Ltd 2007 Page 8 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications Optimised Base Drive To minimize losses in the primary switching transistor (Q1) its base current is carefully controlled. To minimize turn-on losses, the base current is initially forced to a maximum value I BASMAX for a time T FON (the force-on or “FON” pulse). For the remainder of the on-time the base current is reduced to a lower value such that the on-state collector voltage is maintained at a preset target voltage, thereby minimizing turn-off time and consequent losses. During this period, T PBD, the so called “proportional base drive” (PBD) current is referred to as IBASPBD. Aux Supply Bypass transistor Raux AUX Qon PBD BAS Q1 FON T PBD Qoff GND 0V Figure 7: Primary Switch (Q1) Base Drive The BAS pin (see Figure 7) is driven by two transistors, Qon and Qoff. Qon provides I BASMAX during T FON and IBASPBD during the remainder of the on-period. Transistor Qoff provides a low-resistance (RBASCLAMP) path to GND during the off-period to ensure rapid turn-off of the primary switch, Q1. I BASPBD is set by the PBD system within the controller but IBASMAX is determined by the external resistor Raux and the Aux Supply voltage. IBASMAX IBAS VCE T FON T PBD Figure 8: Base Driver Current Waveforms Product data © Cambridge Semiconductor Ltd 2007 Page 9 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications IBASPBD is controlled by monitoring the voltage at the COL pin during T PBD; base current is increased progressively as VCOL rises above threshold V CREF(see Figure 9). The desired on-state V CE of the switching transistor is set by capacitors Cp and Ccol (see Figure 3), the COL pin capacitance (CINCOL) and VCREF. IB A S P B D V C R EF VCO L Figure 9: IBASPBD characteristic Power Control Load conditions are sensed on a cycle-by-cycle basis via the CS pin. When low levels of output power demand are detected, the controller progressively reduces the switching duty cycle to reduce power consumption and to improve output voltage regulation. Power demand causes increase in duty up to the maximum, or until Overload is detected. The voltage at the CS pin is compared to two thresholds, one nominally a t GND voltage (VOCPL) to generate an internal signal OCPL and the other at a negative threshold (VOCPH) to generate an internal signal OCPH. The controller samples OCPL a short time (T OCPL) after turn-on of the primary switch. A negative voltage at the CS pin indicates power demand so the controller increases the switching duty up to the maximum; conversely a positive voltage causes a decrease in duty. Excessive primary switch current, detected via OCPH, terminates the on -period of the primary switch to limit power delivery (Overload mode). High levels of overload (when the converter output voltage held is low by the load) causes OCPH to trigger soon after turn-on of the primary switch. This condition is detected by the controller sampling OCPH at time T FBTHR after turn-on. If OCPH triggers within this time, the controller changes to Foldback mode. To prevent mis-triggering, OCPH is blanked for a short period T CSBLANK after turn-on. Product data © Cambridge Semiconductor Ltd 2007 Page 10 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications The effective thresholds for current through the primary switch for both power reduction (OCPL) and overload (OCPH) are programmed by the current-sense resistors connected to the CS pin as shown in Figure 10. ICSBIAS OCPH threshold (-ve) OCPH Current sense comparators GND CS OCPL GND R2 Rcs Primary switch current Figure 10: Current Sense Diagram The internal current source (ICSBIAS) develops an offset voltage across the series resistor (R2 in Figure 10) so setting OCPL current threshold. Switch current in excess of overload (OCPH) is detected using a fixed threshold voltage but the contribution from the offset voltage across R2 has to be taken into account. IOCPL threshold current = (V OCPL + ICSBIAS.R2)/Rcs IOCPH threshold current = (V OCPH + ICSBIAS.R2)/Rcs R2 VOCPH I OCPL VOCPL I OCPH I OCPH I CSBIAS I OCPL I CSBIAS Rcs VOCPH VOCPL I OCPH I OCPL Note: IOCPL, I OCPH, VOCPH ICSBIAS are all positive magnitude in these formulae Product data © Cambridge Semiconductor Ltd 2007 Page 11 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications Protection Features Collector De-saturation (Over Voltage) Protection (COVP) To protect the primary switch from excessive power dissipation , the on-state voltage of the primary switching transistor is limited by the controller. The controller will go to Foldback mode if the COL pin voltage is greater than VCOVP at the end of the on-time for four consecutive cycles. Over-temperature Protection (OTP) Temperature sensing is integrated with the controller. If the temperature of the die rises above the shutdown temperature, T SH, the BAS output is inhibited. It restarts once the temperature has fallen more than T SH (HYST) below T SH. In typical applications “hiccup” operation will occur. While BAS is inhibited, the device is active and draws IDDW AKE. This causes VDD to fall since auxiliary power is not provided by the transformer. Once VDD reaches VUVDTHR, the controller enters the Sleep state and IDD falls to I DDSLEEP allowing VDD to rise again (via the resistors Vht1 and Vht2). When VDD reaches VOVDTHR reset occurs and the controller re-starts. If the die temperature is below T SH, BAS operation continues but if it is still above T SH, BAS operation ceases after a short period and the hiccup cycle repeats. Primary Switch Over-current Protection (OCP) To protect the primary switch, the base drive is turned off if the primary switch current rises too high, sensed via the CS input voltage falling below a preset negative threshold VOCPH. See also Power Control on page 10. Output Overload/Short-circuit Protection If the application circuit is overloaded beyond a certain limit the controller goes into Foldback mode with reduced duty cycle, protecting the primary switch by reducing its power dissipation. Transition to Foldback mode is triggered by the CS pin voltage crossing the VOCPH threshold within a time T FBTHR of the start of the FON pulse. This typically happens when the load holds the output voltage low. See also Power Control on page 10. Under Voltage Protection The controller is prevented from operating if the V DD supply is inadequate (VDD < V UVDTHR). Once the controller has stopped operation it will not restart until the VDD supply voltage rises above V OVDTHR. Product data © Cambridge Semiconductor Ltd 2007 Page 12 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications ABSOLUTE MAXIMUM RATINGS CAUTION: Permanent damage may result if a device is subjected to operating conditions at or in excess of absolute maximum ratings. Parameter Symbol Condition Min Max Units 4.6 V Supply voltage VDD Input voltage AUX VAUX -0.5 VDD + 0.5 V Input voltage BAS VBAS -0.5 VDD + 0.5 V Input voltage CS VCS -0.5 VDD + 0.5 V Input voltage COL VCOL -0.5 VDD + 0.5 V Pin current VDD IDD -100 30 mA Pin current AUX IAUX -100 100 mA -100 100 1 mA Tj < 125 °C -100 220 mA Tj < 100 °C -100 400 mA -100 100 mA During PBD: ESD diode limit, input is high impedance -100 100 mA During turn-on transient (ACTICLAMP active) -250 250 mA During resonance off period -125 250 mA All other conditions Pin current BAS Pin current CS Pin current COL IBAS While Qoff is on (Figure 7), base duty < 30% ICS ICOL Junction temperature TJ -25 125 o C Storage temperature TSTOR -40 150 o C 260 o C Lead temperature (soldering, 10 s) ESD withstand 1 TL Human body model, JESD22-A114 Charged device model, ANSI-ESD-STM5.3.1 2 kV 500 V IBAS can be higher if controller is active and not in PBD or FON, up to V BAS = VDD Product data © Cambridge Semiconductor Ltd 2007 Page 13 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications NORMAL OPERATING CONDITIONS Parameter Supply voltage Symbol Condition Min Typ Max Units VDD VDD pin, limited by internal regulator 3.1 3.3 3.5 V TJ Over temperature protection operates at higher temperatures -25 25 100 ºC Tj = 25 C, VDD=VDDREG(R) 9.7 12.1 14.5 MHz Temperature coefficient -35 Junction temperature Internal digital clock frequency Switching frequency, Normal mode FCLK FCLKTC FMAX FMIN TRESMIN Transformer resonance time TRESMAX Supply current IDD Determined by TRES (FCLK in MHz) Natural resonance of transformer and associated capacitances. FCLK in MHz. 5 kHzC FCLK / 61 MHz FCLK / 490 MHz 35 / FCLK µs 280 / FCLK µs Limit externally 30 -1 mA ELECTRICAL CHARACTERISTICS Unless otherwise stated: 1. Min and Max electrical characteristics apply over normal operating conditions . 2. Typical electrical characteristics apply at T J = T JTYP and VDD = VDDTYP 3. Functionality and performance is not defined when a device is subjected to conditions outside the range of normal operating conditions and device reliability may be compromised. 4. For parameters dependent on F CLK, the value of F CLK,in MHz should be used in calculations. VDD Pin Parameter Symbol Condition VDDREG(R) Active state, 2.5 mA < IDD < 30 mA VDDREG(S) Start-up state, 2.5 mA < IDD < 30 mA Quiescent current IDDSLEEP Sleep state, VDD < VUVDTHR Residual supply current IDDW AKE Start-up & Active states, Normal mode (VDDREG(R) – 300 mV) < VDD and VDD < (VDDREG(R) - 100 mV) OVD threshold, Sleep VOVDTHR UVD threshold VUVDTHR Regulation voltage VDDREG(R) - VUVDTHR Min Typ Max Units 3.1 3.3 3.5 V 4 V 8 µA 0.5 2.5 mA Sleep state 3.5 4.6 V Start-up and Active states 2.7 3.2 V IDD < 30 mA 150 Condition Min mV AUX Pin Parameter Symbol Input current IAUXMAX AUX pin voltage VAUXFON Product data © Cambridge Semiconductor Ltd 2007 BAS = 800 mV 0 C < TJ < 100 C Typ Max Units 100 mA IAUX = 10 mA 0.84 1.22 V IAUX = 80mA 1.2 1.64 V Page 14 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications CS Pin Parameter Symbol OCPH comparator threshold VOCPH OCPL comparator threshold VOCPL OCPH comparator response time TOCP Bias current ICSBIAS Condition Min 0 C < TJ < 100 C Typ Max Units -260 -235 mV -5 5 mV 0.1 µs 40 67.5 µA 41.5 59.5 µA Step CS input from VCS > -200 mV to VCS < -300 mV 0 C < TJ < 100 C Tj = 25C TOCPL FCLK in MHz 19 / FCLK - 0.06 µs TCSBLANK FCLK in MHz 4 / FCLK - 0.06 µs TFBTHR FCLK in MHz 26 / FCLK - 0.06 µs Parameter Symbol Condition Base drive current IBASMAX Base clamp turn-off resistance OCPL sampling time Blanking period Foldback threshold time BAS Pin Duty cycle Min Typ Max Units Limit by external resistor 100 mA RBASCLAMP VBAS = 400 mV 8.5 Ω DNORMAL Normal mode 43 % Standby mode 0 C < TJ < 100 C 100 230 ns Normal, Foldback & Power Burst modes. 0 C < TJ < 100 C 400 705 ns Force-on period (depends on FCLK) TFON Minimum on-period TONMIN Standby (FCLK in MHz) 20 / FCLK µs Maximum off-period TOFFMAX Standby (FCLK in MHz) 1920 / FCLK + TRES µs NBURST Burst length, number of converter cycles 22144 cycles TBURSTCYCMIN Minimum converter cycle period in 2 Power Burst mode (FCLK in MHz) 39 / FCLK µs NFOLD Foldback duration between bursts, number of converter cycles 18326 cycles TFOLDCYCMIN Converter period in Foldback mode (FCLK in MHz) 900 / FCLK + TRES µs TOFFEXTMIN Extended off time (FCLK in MHz) 896 / FCLK µs Power Burst mode Foldback mode 2 3 3 Minimum converter period = T RES + T ONMIN Minimum converter period = T RES + T OFFEXT + T ONMIN Product data © Cambridge Semiconductor Ltd 2007 Page 15 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications COL Pin Parameter Symbol Rising edge comparator threshold Condition Min ICRISE 0.4 mA Falling edge comparator threshold ICFALL -0.4 mA Collector overvoltage comparator threshold VCOVP PBD threshold voltage VCREF Intercept of characteristic 10 mA < IBAS < 80mA (see Figure 11) V 0.76 1.1 V -650 TJ < 100 C CINCOL TACT VCOL = 1 V Units 0.9VDD 200 Input leakage current ACTICLAMP duration after FON Max 0.7VDD PBD transconductance Input capacitance Typ 25 28 mAV 650 nA 31 pF Standby mode (FCLK in MHz) 3 / FCLK – 0.06 µs Normal, Foldback and Power Burst modes (FCLK in MHz) 4 / FCLK – 0.06 µs -1 IBAS (mA) 100 80 60 40 20 1.0 V CREF V COL (V) 2.0 Figure 11: COL/BAS Transconductance (typical, at 25 °C) Product data © Cambridge Semiconductor Ltd 2007 Page 16 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications THERMAL CIRCUIT PROTECTION Parameter Symbol Condition Min Typ Max Thermal shutdown temperature TSH At junction 105 115 125 Thermal shutdown hysteresis TSH (HYST) At junction 35 Units o C o C PACKAGE THERMAL RESISTANCE CHARACTERISTICS Conditions: 1. Controller IC mounted on typical PCB (1.6 mm thick, 35 µm copper, CEM1); 2. θJP measured to pin terminal of device at the surface of the PCB. Package Junction-to-pin θJP (Typical) Junction-to-ambient θJA (Typical) Units SOT23-6 60 170 °C / W SOP-8 70 140 °C / W PDIP-8 35 105 °C / W PACKAGE AND ORDERING INFORMATION Package Marking The PDIP-8 (C2474PW1) and SOP-8 (C2473PX1) packages are marked with the full product type number. The SOT23-6 package (C2472PX2) is marked with a short code FA as illustrated in Figure 12. C2472PX2 product short code FA Lot dependent code XX (varies) FAXX Figure 12: C2472PX2 SOT23-6 Package Marking Ordering Type Package C2472PX2 SOT23-6 C2473PX1 SOP-8 C2474PW1 PDIP-8 Packing Form Order 7” Tape & Reel C2472PX2-TR7 13” Tape & Reel C2472PX2-TR13 7” Tape & Reel C2473PX1-TR7 13” Tape & Reel C2473PX1-TR13 Tube C2474PW1-T1 For further package and ordering information please contact CamSemi. Product data © Cambridge Semiconductor Ltd 2007 Page 17 of 18 DS-1423-0709C 26-Sep-2007 C2472, C2473 and C2474 Datasheet RDFC Controllers for Offline Applications DATASHEET STATUS The status of this Datasheet is shown in the footer. Always refer to the most current version. Datasheet Status Product Status Definition Product preview In development The Datasheet contains target specifications relating to design and development of the described IC product. Application circuits are illustrative only. Specifications are subject to change without notice. Preliminary In qualification The Datasheet contains preliminary specifications relating to functionality and performance of the described IC product. Application circuits are illustrative only. Specifications are subject to change without notice. Product data In production The Datasheet contains specifications relating to functionality and performance of the described IC product. Application circuits are illustrative only. Specifications are subject to change without notice. CONTACT DETAILS Cambridge Semiconductor Ltd St Andrew’s House St Andrew’s Road Cambridge CB4 1DL United Kingdom Phone: Fax: Email: Web: +44 (0)1223 446450 +44 (0)1223 446451 [email protected] www.camsemi.com DISCLAIMER The product information provided herein is believed to be accurate and is provided on an “as is” basis. Cambridge Semiconductor Ltd (CamSemi) assumes no responsibility or liability for the direct or indirect consequences of use of the information in respect of any infringement of patents or other rights of third parties. Cambridge Semiconductor Ltd does not grant any licence under its patent or intellectual property rights or the rights of other parties. Any application circuits described herein are for illustrative purposes only. In respect of any application of the product described herein Cambridge Semiconductor Ltd expressly disclaims all warranties of any kind, whether express or implied, including, but not limited to, the implied warranties of merchantability, fitness for a particular purpose and non-infringement. No advice or information, whether oral or written, obtained from Cambridge Semiconductor Ltd shall create any warranty of any kind. Cambridge Semiconductor Ltd shall not be liable for any direct, indirect, incidental, special, consequential or exemplary damages, howsoever caused including but not limited to, damages for loss of profits, goodwill, use, data or other intangible losses. The products and circuits described herein are subject to the usage conditions and end application exclusions as outlined in Cambridge Semiconductor Ltd Terms and Conditions of Sale which can be found at www.camsemi.com/legal . Cambridge Semiconductor Ltd reserves the right to change specifications without notice. To obtain the most current product information available visit www.camsemi.com or contact us at the address shown above. Product data © Cambridge Semiconductor Ltd 2007 Page 18 of 18 DS-1423-0709C 26-Sep-2007