Datenblatt-Suchmaschine für elektronische Bauteile |
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LM21305 Datenblatt(PDF) 9 Page - Texas Instruments |
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LM21305 Datenblatt(HTML) 9 Page - Texas Instruments |
9 / 33 page EA REF CBOOT LDO2 2.5V SS PVIN AVIN Input UVLO Output UV, OV OTP PGOOD EN PWM Control Logic AGND PGND OSC/ Sync LDO1 5V OTP FREQ 2V5 5V0 SW FB COMP L1 C3 C2 C1 C6 C5 R4 R1 C4 C5 SYNC VIN VOUT C7 R1 UVLO HS FET OCP Z cross LS FET OCP PWM Slope Comp OVP SW Rev OCP ISENSE PWM + - 1.2V Non- overlap Non- overlap LM21305 www.ti.com SNVS639F – DECEMBER 2009 – REVISED MARCH 2013 BLOCK DIAGRAM OPERATION DESCRIPTION The LM21305 employs peak current-mode control. The 0.598V reference is compared to the feedback signal at the error amplifier (EA). The PWM modulator block compares the on-time current sense information with the summation of the EA output (control voltage) and slope compensation. The PWM modulator outputs on/off signals to the high-side and low-side MOSFET drivers. Adaptive dead-time control is applied to the PWM output such that shoot through current is avoided. The drivers then amplify the PWM signals to control the integrated high-side and low-side MOSFETs. SWITCHING REGULATOR The LM21305 employs a buck type (step-down) converter architecture. It utilizes many advanced features to achieve excellent voltage regulation and efficiency. This easy-to-use regulator features two integrated switches and is capable of supplying up to 5A of continuous output current. The regulator utilizes peak current-mode control with slope compensation scaled with switching frequency to optimize stability and transient response over the entire output voltage and switching frequency ranges. Peak current-mode control also provides inherent line feed-forward, cycle-by-cycle current limiting, and easy loop compensation. The switching frequency can be adjusted between 300 kHz and 1.5 MHz. The device can operate with a small external L-C filter and still provide very low output voltage ripple. The precision internal voltage reference allows the output to be set as low as 0.598V. Using an external compensation circuit, the regulator bandwidth can be selected based on the switching frequency to provide fast load transient response. The switching regulator is specially designed for high efficiency operation throughout the load range. Synchronous rectification yields high efficiency for low voltage and heavy load current situations, while discontinuous conduction and diode emulation modes enable high efficiency conversion at lighter load currents. Fault protection features include: high-side and low-side switch current limiting, negative current limiting on the low-side switch, over-voltage protection and thermal shutdown. The device is available in the WQFN-28 package featuring an exposed pad to aid thermal dissipation. The LM21305 can be used in numerous applications to efficiently step-down from a wide range of input rails: 3V to 18V. Copyright © 2009–2013, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Links: LM21305 |
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