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LM25574 数据表(PDF) 8 Page - Texas Instruments |
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LM25574 数据表(HTML) 8 Page - Texas Instruments |
8 / 30 page FB SW RT VIN BST SD 5V S R Q Q AGND IS CLK + SS PRE 3 2 10 6 5 4 7 8 11 9 12 1 SD Ir LM25574 SHUTDOWN STANDBY 7V REGULATOR SYNC SYNC OSCILLATOR RAMP OUT PGND CLK CLK COMP ERROR AMP R3 21k C3 470p C9 22 R6 1.65k R5 5.11k L1 100 PH C7 0.022 C8 0.47 D1 CMSH2-60M 13 15 14 16 THERMAL SHUTDOWN UVLO UVLO CLK DIS VCC LEVEL SHIFT DRIVER 1.225V 1.225V 0.7V 0.7V R4 24.9k C5 0.022 C6 open R2 OPEN C2 OPEN C4 0.01 C1 1.0 R1 OPEN 7V ± 42V VIN VIN 1.4V PWM C_LIMIT 10 PA 5 PA VIN TRACK SAMPLE and HOLD 2V/A RAMP GENERATOR Ir = (10 PA x (VIN ± VOUT)) + 50 PA LM25574, LM25574-Q1 SNVS483G – JANUARY 2007 – REVISED APRIL 2013 www.ti.com TYPICAL APPLICATION CIRCUIT AND BLOCK DIAGRAM Detailed Operating Description The LM25574 switching regulator features all of the functions necessary to implement an efficient high voltage buck regulator using a minimum of external components. This easy to use regulator integrates a 42V N-Channel buck switch with an output current capability of 0.5 Amps. The regulator control method is based on current mode control utilizing an emulated current ramp. Peak current mode control provides inherent line voltage feed- forward, cycle-by-cycle current limiting, and ease of loop compensation. The use of an emulated control ramp reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable processing of very small duty cycles necessary in high input voltage applications. The operating frequency is user programmable from 50kHz to 1MHz. An oscillator synchronization pin allows multiple LM25574 regulators to self synchronize or be synchronized to an external clock. The output voltage can be set as low as 1.225V. Fault protection features include, current limiting, thermal shutdown and remote shutdown capability. The device is available in the TSSOP-16 package. The functional block diagram and typical application of the LM25574 are shown in Typical Application Circuit and Block Diagram. The LM25574 can be applied in numerous applications to efficiently step-down a high, unregulated input voltage. The device is well suited for telecom, industrial and automotive power bus voltage ranges. High Voltage Start-Up Regulator The LM25574 contains a dual-mode internal high voltage startup regulator that provides the Vcc bias supply for the PWM controller and boot-strap MOSFET gate driver. The input pin (VIN) can be connected directly to the input voltage, as high as 42 Volts. For input voltages below 9V, a low dropout switch connects Vcc directly to Vin. In this supply range, Vcc is approximately equal to Vin. For Vin voltage greater than 9V, the low dropout switch is disabled and the Vcc regulator is enabled to maintain Vcc at approximately 7V. The wide operating range of 6V to 42V is achieved through the use of this dual mode regulator. The output of the Vcc regulator is current limited to 25mA. Upon power up, the regulator sources current into the capacitor connected to the VCC pin. When the voltage at the VCC pin exceeds the Vcc UVLO threshold of 5.35V and the SD pin is greater than 1.225V, the output switch is enabled and a soft-start sequence begins. The output switch remains enabled until Vcc falls below 5.0V or the SD pin falls below 1.125V. 8 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Product Folder Links: LM25574 LM25574-Q1 |
类似零件编号 - LM25574 |
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类似说明 - LM25574 |
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