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MCP1252 データシート(PDF) 10 Page - Microchip Technology |
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MCP1252 データシート(HTML) 10 Page - Microchip Technology |
10 / 20 page ![]() MCP1252/3 DS20001752C-page 10 2002-2014 Microchip Technology Inc. 4.2 Power Efficiency The power efficiency, , is determined by the mode of operation. In boost mode, the efficiency is approximately half of a linear regulator. In buck mode, the efficiency is approximately equal to that of a linear regulator. The following formulas can be used to approximate the power efficiency with any significant amount of output current. At light loads, the quiescent current of the device must be taken into consideration. EQUATION 4-1: 4.3 Shutdown Mode Driving SHDN low places the MCP1252 or MCP1253 in a low-power shutdown mode. This disables the charge pump switches, oscillator and control logic, reducing the quiescent current to 0.1 µA (typical). The PGOOD output is in a high-impedance state during shutdown. 4.4 PGOOD Output The PGOOD output is an open-drain output that sinks current when the regulator output voltage falls below 0.93VOUT (typical). The output voltage can either be fixed when the selectable output device is chosen (MCP1252-33X50, MCP1253-33X50) or adjustable from an external resistive divider when the adjustable device is chosen (MCP1252-ADJ, MCP1253-ADJ). If the regulator output voltage falls below 0.93VOUT (typical) for less than 200 µsec and then recovers, glitch-immunity circuits prevent the PGOOD signal from transitioning low. A 10 k to 1 M pull-up resistor from PGOOD to VOUT may be used to provide a logic output. Connect PGOOD to GND or leave unconnected if not used. 4.5 Soft-Start and Short-Circuit Protection The MCP1252 and MCP1253 feature foldback short- circuit protection. This circuitry provides an internal soft-start function by limiting in-rush current during startup and also limits the output current to 200 mA (typical) if the output is shorted to GND. The internal soft-start circuitry requires approximately 300 µsec, typical with a 5V output, from either initial power-up or release from shutdown for the output voltage to be in regulation. 4.6 Thermal Shutdown The MCP1252 and MCP1253 feature thermal shutdown with temperature hysteresis. When the die temperature exceeds 160°C, typically, the device shuts down. When the die cools by 15°C, typically, the device automatically turns back on. If high die temperature is caused by output overload and the load is not removed, the device will turn on and off, resulting in a pulse output. 5.0 APPLICATIONS The MCP1252 and MCP1253 are inductorless, positive-regulated, charge pump DC/DC converters. A typical circuit configuration for the fixed output version is depicted in Figure 5-1. The adjustable version is depicted in Figure 5-2. FIGURE 5-1: Typical Circuit Configuration for Fixed Output Device. FIGURE 5-2: Typical Circuit Configuration for Adjustable Output Device. BOOST P OUT P IN ------------- V OUT I OUT V IN 2 I OUT ------------------------------------ V OUT V IN 2 ------------------ == = BUC K P OUT P IN ------------- V OUT I OUT V IN I OUT -------------------------------- V OUT V IN ------------- == = MCP1252-33X50 C+ CFLY 6 5 C- VIN SHDN 3 7 OFF ON Shutdown Control + 2.7V to 5.5V CIN GND SELECT PGOOD VOUT 8 1 2 + COUT RPU PGOOD Flag To PIC® +5.0V ±2.5% SELECTABLE OUTPUT VOLTAGE 4 CFLY = 1µF CIN = 10 µF COUT = 10 µF Microcontroller RPU = 100 k MCP1252-ADJ C+ CFLY 6 5 C- VIN SHDN 3 7 OFF ON Shutdown Control + 2.7V to 5.5V CIN GND FB PGOOD VOUT 8 1 2 + COUT RPU PGOOD Flag To PIC® +4.0V ADJUSTABLE OUTPUT VOLTAGE R2 R1 4 VOUT = 1.21V (1 + R1/R2) Microcontroller CFLY = 1µF CIN = 10 µF COUT = 10 µF RPU = 100 k R1 = 23.2 k R2 = 10 k + |
同様の部品番号 - MCP1252_14 |
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同様の説明 - MCP1252_14 |
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