PAC5220 Datasheet, PDF (22/73 Pages) Active-Semi, Inc – Power Application Controller

Figure 10-4. AC/DC Flyback Mode
VHM
PAC5220
VP
DRM
CSM
PAC5220
Power Application Controller
V (120V/230V)
AC
V (12V typical)
P
The MMSS detects and selects between high-side and low-side mode during start up based on the placement of
the current sense resistor and the CSM pin voltage. It employs a safe start up mode with a 9.5kHz switching
frequency until VP exceeds 4.3V under-voltage-lockout threshold, then transitions to the 45kHz default switching
frequency for at least 6ms to bring VP close to the target voltage, before enabling the linear regulators. Any extra
load should only be applied after the supplies are available and the microprocessor has initialized. The switching
frequency can be reconfigured by the microprocessor to be 181kHz to 500kHz in the high switching frequency
mode for battery-based applications, and to be 45kHz to 125kHz in the low switching frequency mode for AC
applications. Upon initialization, the microcontroller must reconfigure the MMSS to the desired settings for
VP regulation voltage, switching mode, switching frequency, and VHM clamp. Refer to the PAC application notes
and user guide for MMSS controller design and programming.
If a stable external 5V to 12V power source is available, it can power the VP main supply and all the linear
regulators directly without requiring the MMSS controller to operate. In such applications, V HM can be connected
directly to VP and the microcontroller should disable the MMSS upon initialization to reduce power loss.
10.3.2. Linear Regulators
The MMPM includes up to four linear regulators. The system supply regulator is a medium voltage regulator that
takes the VP supply and sources up to 200mA at REGO until VSYS, externally coupled to REGO, reaches 5V. This
allows a properly rated external resistor to be connected from REGO to VSYS to close the current loop and
offload power dissipation between VP and VSYS. Once VSYS is above 4V, the three additional 40mA linear
regulators for VCCIO, VCC33, and VCC18 supplies sequentially power up. Figure 10-5 shows typical circuit
connections for the linear regulators. For 5V I/O systems, short the VCCIO pin to VSYS to bypass the VCCIO
regulator. For 3.3V I/O systems, the VCCIO regulator generates 3.3V. The VCC33 and VCC18 regulators generate
3.3V and 1.8V, respectively. When VSYS, VCCIO, VCC33, and VCC18 are all above their respective power good
thresholds, and the configurable power on reset duration has expired, the microcontroller is initialized.
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Rev 1.0‒February 25, 2014