DPA-Switch
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DPA422-426 DPA-Switch™ Family Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications Product Highlights Highly Integrated Solution • Eliminates up to 50 external components–saves space, cost • Integrates 220 V high frequency MOSFET, PWM control • Lower cost plastic DIP surface mount (G package) and through-hole (P package) options for designs ≤35 W • Thermally efficient TO-263-7C (R package) option for high power applications Superior Performance and Flexibility • Eliminates all external current sensing circuitry • Built-in auto-restart for output overload/open loop protection • Pin selectable 300/400 kHz fixed frequency • Wide input (line) voltage range: 16-75 VDC • Externally programmable current limit • Source connected tab reduces EMI • Line undervoltage (UV) detection: meets ETSI standards • Line overvoltage (OV) shutdown protection • UV/OV limits gate drive voltage for synchronous rectification • Fully integrated soft-start for minimum stress/overshoot • Supports forward or flyback topology • Cycle skipping: regulation to zero load without pre-load • Hysteretic thermal shutdown for automatic fault recovery • RoHS compliant P and G package options RESET/ CLAMP CIRCUIT Typical Forward Converter Application. Output Power Table 36-75 VDC Input Range (Forward)2 Total Device Dissipation3 Energy Efficient Extremely low consumption at no-load Cycle skipping at light load for high standby efficiency Applications • PoE applications, VoIP phones, WLAN, security cameras • Telco central office equipment: xDSL, ISDN, PABX • Distributed power architectures (24 V/48 V bus) • Industrial controls 36-75 VDC Input Range (Flyback)2 Total Device Dissipation3 The DPA-Switch IC family is a highly integrated solution for DC-DC conversion applications with 16‑75 VDC input. DPA-Switch uses the same proven topology as TOPSwitch®, cost effectively integrating a power MOSFET, PWM control, fault protection and other control circuitry onto a single CMOS chip. High performance features are enabled with three user configurable pins. Hysteretic thermal shutdown is also provided. In addition, all critical parameters (i.e. current limit, frequency, PWM gain) have tight temperature and absolute tolerance, to simplify design and reduce system cost. Table 1. Output Power Table. Notes: 1. Maximum output power is limited by device internal current limit. 2. See Applications Considerations section for complete description of assumptions and for output powers with other input voltage ranges. 3. For device dissipation of 1.5 W or below, use P or G packages. Device dissipation above 1.5 W is possible with R package. 4. Packages: P: DIP-8, G: SMD-8, R: TO-263-7C. For lead-free package options, see Part Ordering Information. 5. Available in R package only. 6. Due to higher switching losses, the DPA425 may not deliver additional power compared to a smaller device. 7. Available in P and G package only. 8. DPA422 not recommended for new designs, use DPA423 instead.

INTERNAL SUPPLY SHUNT REGULATOR/ ERROR AMPLIFIER - SOFT START CURRENT LIMIT ADJUST SOFT START LINE SENSE CONTROLLED TURN-ON GATE DRIVER STOP SOFTSTART DMAX DCMAX CLOCK 300/400 kHz CURRENT LIMIT COMPARATOR HYSTERETIC THERMAL SHUTDOWN STOP LOGIC SHUTDOWN/ AUTO-RESTART EXTERNAL CURRENT LIMIT (X) LEADING EDGE BLANKING CYCLE SKIPPING Figure 2. Functional Block Diagram. Pin Functional Description DRAIN (D) Pin: High-voltage power MOSFET drain output. The internal startup bias current is drawn from this pin through a switched highvoltage current source. Internal current limit sense point for drain...

DPA-Switch Family Functional Description DPA-Switch is an integrated switched mode power supply chip that converts a current at the control input to a duty cycle at the open drain output of a high-voltage power MOSFET. During normal operation the duty cycle of the power MOSFET decreases linearly with increasing CONTROL pin current as shown in Figure 4. A patented high-voltage CMOS technology allows both the high-voltage power MOSFET and all the low voltage control circuitry to be cost effectively integrated onto a single monolithic chip. h addition to the standard TOPSwitch features, such...

DPA422-426 overloaded output exists, the feedback loop will close, providing external CONTROL pin current, before the CONTROL pin voltage has had a chance to discharge to the lower threshold voltage of approximately 4.8 V (internal supply undervoltage lockout threshold). When the externally fed current charges the CONTROL pin to the shunt regulator voltage of 5.8 V, current in excess of the consumption of the chip is shunted to SOURCE through resistor RE as shown in Figure 2. This current flowing through RE controls the duty cycle of the power MOSFET to provide closed loop regulation. The...

DPA422-426 The maximum duty cycle, DCMAX is set at a default maximum value of 75% (typical). However, by connecting the LINE-SENSE to the DC input bus through a resistor with appropriate value, the maximum duty cycle can be made to decrease from 75% to 33% (typical) as shown in Figure 7 when input line voltage increases (see Line Feed-Forward with DCMAX Reduction). Minimum Duty Cycle and Cycle Skipping To maintain power supply output regulation, the pulse width modulator reduces duty cycle as the load at the power supply output decreases. This reduction in duty cycle is proportional to the...

DPA422-426 saturation due to large load transients in forward converter applications. DCMAX of 33% at the OV threshold was chosen to ensure that the power capability of the DPA-Switch is not restricted by this feature under normal operation. Remote ON/OFF Remote ON/OFF control describes operation where the IC is turned on or off for long periods as opposed to the cycle-bycycle on/off control, which is described in the Synchronization section below. DPA-Switch can be turned on or off by controlling the current into the LINE-SENSE pin or out from the EXTERNAL CURRENT LIMIT pin (see Figure 7)....