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EL7534IYZ-T13 Datasheet(PDF) 6 Page - Intersil Corporation |
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EL7534IYZ-T13 Datasheet(HTML) 6 Page - Intersil Corporation |
6 / 8 page 6 FN7431.5 August 16, 2005 Applications Information Product Description The EL7534 is a synchronous, integrated FET 600mA step- down regulator which operates from an input of 2.5V to 6V. The output voltage is user-adjustable with a pair of external resistors. The internally-compensated controller makes it possible to use only two ceramic capacitors and one inductor to form a complete, very small footprint 600mA DC:DC converter. Start-Up and Shut-Down When the EN pin is tied to VIN, and VIN reaches approximately 2.4V, the regulator begins to switch. The output voltage is gradually increased to ensure proper soft- start operation. When the EN pin is connected to a logic low, the EL7534 is in the shut-down mode. All the control circuitry and both MOSFETs are off, and VOUT falls to zero. In this mode, the total input current is less than 1µA. When the EN reaches logic HI, the regulator repeats the start-up procedure, including the soft-start function. PWM Operation In the PWM mode, the P channel MOSFET and N channel MOSFET always operate complementary. When the PMOSFET is on and the NMOSFET off, the inductor current increases linearly. The input energy is transferred to the output and also stored in the inductor. When the P channel MOSFET is off and the N channel MOSFET on, the inductor current decreases linearly, and energy is transferred from the inductor to the output. Hence, the average current through the inductor is the output current. Since the inductor and the output capacitor act as a low pass filter, the duty cycle ratio is approximately equal to VO divided by VIN. The output LC filter has a second order effect. To maintain the stability of the converter, the overall controller must be compensated. This is done with the fixed internally compensated error amplifier and the PWM compensator. Because the compensations are fixed, the values of input and output capacitors are 10µF to 22µF ceramic. The inductor is nominally 1.8µH, though 1.5µA to 2.2µH can be used. 100% Duty Ratio Operation EL7534 utilizes CMOS power FET's as the internal synchronous power switches. The upper switch is a PMOS and lower switch a NMOS. This not only saves a boot capacitor, it also allows 100% turn-on of the upper PFET switch, achieving VO close to VIN. The maximum achievable VO is, Where RL is the DC resistance on the inductor and RDSON1 the PFET on-resistance, nominal 70m Ω at room temperature with tempco of 0.2m Ω/°C. As the input voltage drops gradually close or even bellow the preset VO, the converter gets into 100% duty ratio. At this condition, the upper PFET needs some minimum turn-off time if it is turned off. This off-time is related to input/output conditions. This makes the duty ratio appears randomly and increases the output ripple somewhat until the 100% duty ratio is reached. Larger output capacitor could reduce the random-looking ripple. Users need to verify if this condition FIGURE 12. PACKAGE POWER DISSIPATION vs AMBIENT TEMPERATURE FIGURE 13. PACKAGE POWER DISSIPATION vs AMBIENT TEMPERATURE Performance Curves and Waveforms (Continued) All waveforms are taken at VIN=3.3V, VO=1.8V, IO=600mA with component values shown on page 1 at room ambient temperature, unless otherwise noted. JEDEC JESD51-3 LOW EFFECTIVE THERMAL CONDUCTIVITY TEST BOARD 0.7 0.6 0.4 0.3 0.2 0.1 0 0 255075 100 150 AMBIENT TEMPERATURE (°C) 85 607mW θ JA = 206 °C /W MS OP 10 0.5 125 JEDEC JESD51-7 HIGH EFFECTIVE THERMAL CONDUCTIVITY TEST BOARD 1.2 1 0.4 0 0 255075 100 150 AMBIENT TEMPERATURE (°C) 85 1.087W θ JA = 115 °C /W MS OP 10 0.8 0.2 0.6 125 VO VIN RL RDSON1 + () I O × – = EL7534 |
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