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AP2014-AN Datasheet(PDF) 10 Page - Anachip Corp |
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AP2014-AN Datasheet(HTML) 10 Page - Anachip Corp |
10 / 12 page AP2014/A Synchronous PWM Controller Anachip Corp www.anachip.com.tw Rev. 1.2 Nov 29, 2005 10/12 Function Descriptions Introduction The AP2014 is a fixed frequency, voltage mode synchronous controller and consists of a precision reference voltage, an error amplifier, an internal oscillator, a PWM comparator, 0.5A peak gate driver, soft-start and shutdown circuits (see Block Diagram). The output voltage of the synchronous converter is set and controlled by the output of the error amplifier; this is the amplified error signal from the sensed output voltage and the reference voltage. This voltage is compared to a fixed frequency linear sawtooth ramp and generates fixed frequency pulses of variable duty-cycle, which drives the two N-channel external MOSFETs.The timing of the IC is provided through an internal oscillator circuit which uses on-chip capacitor to set the oscillation frequency to 200 KHz (400 KHz for “A” version). Soft-Start The AP2014 has a programmable soft-start to control the output voltage rise and limit the current surge at the start-up. To ensure correct start-up, the soft-start sequence initiates when the VC and VCC rise above their threshold (3.3V and 4.2V respectively) and generates the Power On Reset (POR) signal. Soft-start function operates by sourcing an internal current to charge an external capacitor to about 3V. Initially, the soft-start function clamps the E/A’s output of the PWM converter. As the charging voltage of the external capacitor ramps up, the PWM signals increase from zero to the point the feedback loop takes control. Short-Circuit Protection The outputs are protected against the short circuit. The AP2014 protects the circuit for shorted output by sensing the output voltage (through the external resistor divider). The AP2014 shuts down the PWM signals, when the output voltage drops below 0.6V (0.4V for AP2014A). The AP2014 also protects the output from over-voltaging when the control FET is shorted. This is done by turning on the sync FET with the maximum duty cycle. Under-Voltage Lockout The under-voltage lockout circuit assures that the MOSFET driver outputs remain in the off state whenever the supply voltage drops below set parameters. Lockout occurs if VC and VCC fall below 3.3V and 4.2V respectively. Normal operation resumes once VC and VCC rise above the set values. IC Quiescent Power Dissipation Power dissipation for IC controller is a function of applied voltage, gate driver loads and switching frequency. The IC's maximum power dissipation occurs when the IC operating with single 12V supply voltage (Vcc=12V and Vc 24V) at 400KHz switching frequency and maximum gate loads. Page 8 show voltage vs. current, when the gate drivers loaded with 1500pF capacitors. The IC's power dissipation results to an excessive temperature rise. This should be considered when using AP2014A for such application. Marking Information (Top View) SOP-8L/PDIP-8L AP2014 X YY WW X Logo Part No. ID code: internal Year: "01" =2001 "02" =2002 Xth week: 01~52 5 8 4 1 AP2014 : 200KHz (OSC) AP2014A : 400KHz (OSC) |
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