ALTAIR05T-800

ALTAIR05T-800 Off-line all-primary-sensing switching regulator Features ■ Constant voltage and constant current output regulation (CV/CC) with no optocoupler ■ Tight regulation also in presence of heavy load transients ■ 800 V avalanche rugged internal power section ■ Quasi-resonant (QR) operation ■ Low standby power consumption ■ Automatic self-supply ■ Input voltage feedforward for mainsindependent cc regulation ■ Output cable drop compensation ■ SO16 package SO16N Applications ■ AC-DC chargers for mobile phones and other hand-held equipments ■ Compact SMPS that requires a precise current and/or voltage regulation Description ALTAIR05T-800 is a high-voltage all-primary sensing switcher intended for operating directly from the rectified mains with minimum external parts. It combines a high-performance lowvoltage PWM controller chip and an 800 V avalanche-rugged power section in the same package. Figure 1. Block diagram +Vout +Vin Is tart -up Vcc Internal supply bus PROTECTION & FEEDFORWARD LOGIC DRAIN SUPPLY & UV LO Vref UVLO Prot CDC Rcdc Rzcd IFF Iout ESTIMATE ZCD/FB BLANKING TIME Vc STARTER 3.3 V TURN-ON LOGIC Vc DEMAG LOGIC Rfb R R Q Q LEB + R S Q 1V Iref - + S/H S S Intern. supp ly bus I FF - UVLO R + Prot + 2.5 V RFF COMP GND IREF Rcomp Cref SOURCE Rsense Ccomp October 2010 Doc ID 17957 Rev 1 1/28 www.st.com 28 Contents ALTAIR05T-800 Contents 1 Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.1 Power section and gate driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.2 High-voltage start-up generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.3 Zero current detection and triggering block . . . . . . . . . . . . . . . . . . . . . . . 13 5.4 Constant voltage operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.5 Constant current operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.6 Voltage feedforward block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.7 Cable drop compensation (CDC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.8 Burst-mode operation at no load or very light load . . . . . . . . . . . . . . . . . . 20 5.9 Soft-start and starter block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.10 Hiccup mode OCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.11 Layout recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 8 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 2/28 Doc ID 17957 Rev 1 ALTAIR05T-800 1 Device description Device description The device combines two silicon in the same package: a low voltage PWM controller and an 800 V avalanche rugged power section. The controller chip is a current-mode specifically designed for offline quasi-resonant flyback converters. The device features a unique characteristic: it is capable of providing constant output voltage (CV) and constant output current (CC) regulation using primary-sensing feedback. This eliminates the need for the optocoupler, the secondary voltage reference, as well as the current sensor, still maintaining quite accurate regulation also in presence of heavy load transients. Additionally, it is possible to compensate the voltage drop on the output cable, so as to improve CV regulation on the external accessible terminals. Quasi-resonant operation is guaranted by means of a transformer demagnetization sensing input that turns on the power section. The same input serves also the output voltage monitor, to perform CV regulation, and the input voltage monitor, to achieve mainsindependent CC regulation (line voltage feedforward). The maximum switching frequency is top-limited below 166 kHz, so that at medium-light load a special function automatically lowers the operating frequency still maintaining the valley switching operation. At very light load, the device enters a controlled burst-mode operation that, along with the built-in high-voltage start-up circuit and the low operating current, helps minimize the standby power. Although an auxiliary winding is required in the transformer to correctly perform CV/CC regulation, the chip is able to power itself directly from the rectified mains. This is useful especially during CC regulation, where the flyback voltage generated by the winding drops below UVLO threshold. However, if ultra-low no-load input consumption is required to comply with the most stringent energy-saving recommendations, then the device needs to be powered via the auxiliary winding. In addition to these functions that optimize power handling under different operating conditions, the device offers protection features that considerably increase end-product’s safety and reliability: auxiliary winding disconnection - or brownout – detection and shorted secondary rectifier - or transformer’s saturation – detection. All of them are auto restart mode. Doc ID 17957 Rev 1 3/28 Pin connection 2 ALTAIR05T-800 Pin connection Figure 2. Pin connection (top view) SOURCE 1 16 DRAIN SOURCE 2 15 DRAIN Vcc 3 14 DRAIN GND 4 13 DRAIN IREF 5 12 N.C. ZCD/FB 6 11 N.A. COMP 7 10 N.A. CDC 8 9 N.A. Note: The copper area for heat dissipation has to be designed under the drain pins Table 1. Pin functions N. 1, 2 Function Power section source and input to the PWM comparator. The current flowing in the MOSFET is sensed through a resistor connected between the pin and GND. The resulting voltage is compared with an internal reference (0.75V max.) to determine MOSFET’s turn-off. The pin SOURCE is equipped with 250 ns blanking time after the gate-drive output goes high for improved noise immunity. If a second comparison level located at 1V is exceeded the IC is stopped and restarted after Vcc has dropped below 5V. 3 Vcc Supply Voltage of the device. An electrolytic capacitor, connected between this pin and ground, is initially charged by the internal high-voltage start-up generator; when the device is running the same generator keeps it charged in case the voltage supplied by the auxiliary winding is not sufficient. This feature is disabled in case a protection is tripped. Sometimes a small bypass capacitor (0.1 µF typ.) to GND might be useful to get a clean bias voltage for the signal part of the IC. 4 GND Ground. Current return for both the signal part of the IC and the gate drive. All of the ground connections of the bias components should be tied to a trace going to this pin and kept separate from any pulsed current return. IREF CC regulation loop reference voltage. An external capacitor has to be connected between this pin and GND. An internal circuit develops a voltage on this capacitor that is used as the reference for the MOSFET’s peak drain current during CC regulation. The voltage is automatically adjusted to keep the average output current constant. 5 4/28 Name Doc ID 17957 Rev 1 ALTAIR05T-800 Table 1. N. Pin connection Pin functions (continued) Name Function 6 ZCD/FB Transformer’s demagnetization sensing for quasi-resonant operation. Input/output voltage monitor. A negative-going edge triggers MOSFET’s turn-on. The current sourced by the pin during ON-time is monitored to get an image of the input voltage to the converter, in order to compensate the internal delay of the current sensing circuit and achieve a CC regulation independent of the mains voltage. If this current does not exceed 50µA, either a floating pin or an abnormally low input voltage is assumed, the device is stopped and restarted after Vcc has dropped below 5V. Still, the pin voltage is sampled-and-held right at the end of transformer’s demagnetization to get an accurate image of the output voltage to be fed to the inverting input of the internal, transconductance-type, error amplifier, whose non-inverting input is referenced to 2.5V. Please note that the maximum IZCD/FB sunk/sourced current has to not exceed ±2 mA (AMR) in all the Vin range conditions (85-265 Vac). No capacitor is allowed between the pin and the auxiliary transformer. 7 COMP Output of the internal transconductance error amplifier. The compensation network is placed between this pin and GND to achieve stability and good dynamic performance of the voltage control loop. 8 CDC Cable drop compensation input. During CV regulation this pin, capable of sinking current, provides a voltage lower than the internal reference voltage (2.5V) by an amount proportional to the dc load current. By connecting a resistor between this pin and ZCD/FB, the CV regulation setpoint is increased proportionally. This allows that the voltage drop across the output cable be compensated and, ideally, that zero load regulation at the externally available terminals be achieved. Leave the pin open if the function is not used. 9-11 N.A Not available. These pins must be left not connected 12 N.C Not internally connected. Provision for clearance on the PCB to meet safety requirements. 13 to 16 DRAIN Drain connection of the internal power section. The internal high-voltage start-up generator sinks current from this pin as well. Pins connected to the internal metal frame to facilitate heat dissipation. Doc ID 17957 Rev 1 5/28 Maximum ratings ALTAIR05T-800 3 Maximum ratings 3.1 Absolute maximum ratings Table 2. Symbol VDS ID Eav Absolute maximum ratings Pin Value Unit -1 to 800 V 1,2, 13-16 Drain current 1 A 1,2, 13-16 Single pulse avalanche energy (Tj = 25°C, ID = 1A) 50 mJ 1,2, 13-16 Drain-to-source (ground) voltage Vcc 3 Supply voltage (Icc < 25mA) Self limiting V IZCD/FB 6 Zero current detector current ±2 mA --- 7, 8 -0.3 to 3.6 V ICDC 8 Maximum sunk current 200 µA Power dissipation @TA = 50°C 0.9 W Junction temperature range -25 to 150 °C Storage temperature -55 to 150 °C Ptot Tj Tstg 3.2 Analog inputs and outputs Thermal data Table 3. Symbol 6/28 Parameter Thermal data Parameter Max. value Unit Rth j-pin Thermal resistance, junction-to-pin 10 Rth j-amb Thermal resistance, junction-to-ambient 110 Doc ID 17957 Rev 1 °C/W ALTAIR05T-800 4 Electrical characteristics Electrical characteristics (TJ = -25 to 125 °C, Vcc = 14 V; unless otherwise specified) Table 4. Electrical characteristics Symbol Parameter Test condition Min. Typ. Max. Unit Power section V(BR)DSS Drain-source breakdown IDSS RDS(on) Coss ID< 100 µA; Tj = 25 °C 800 V VDS = 750 V; Tj = 125 °C (See Figure 4 and note) Off state drain current 80 Id=100 mA; Tj = 25 °C 11 14 Id=100 mA; Tj = 125 °C 22 28 Drain-source ON-state resistance µA Ω Effective (energy-related) output capacitance (See Figure 3) High-voltage start-up generator VStart Min. Drain start voltage Icharge < 100 µA 40 50 60 V Icharge Vcc startup charge current VDRAIN> VStart; VCC