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EL7554IREZ-T7 Datasheet(PDF) 9 Page - Intersil Corporation |
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EL7554IREZ-T7 Datasheet(HTML) 9 Page - Intersil Corporation |
9 / 14 page 9 FN7360.4 May 8, 2006 Detailed Description The EL7554 is a full-feature synchronous 6A step-down regulator capable of up to 96% efficiency. This device operates from 3V to 6V VIN input supply. With internal CMOS power FETs, the device can operate at up to 100% duty ratio, allowing for output voltage range from 0.8V up to nearly VIN.The adjustable high switching frequency of up to 1MHz enables the use of small components, making the whole converter occupy less than 0.58 square inch with components on one side of the PCB. The EL7554 operates at constant frequency PWM mode, making external synchronization possible. Patented on-chip resistorless current-sensing enables current mode control, which provides over-current protection, and excellent step load response. The EL7554 features soft-start and full start-up control, which eliminate the in-rush current and enables users to control the start-up of multiple converters to any configuration with ease. The EL7554 also offers a ±5% voltage margining capability that allows raising and lowering of the supplies derived from the EL7554 to validate the performance and reliability of system cards quickly and easily during manufacturing testing. A junction temperature indicator conveniently monitors the silicon die temperature, saving designers time in the tedious thermal characterization. Start-Up The EL7554 employs a special soft-start to suppress the in- rush current (see Figure 12). The start-up process takes about 2ms and begins when the input voltage reaches about 2.8V and EN pin voltage 2V. When EN is released from LOW, or the converter comes out of thermal shut-down mode, the soft-start process repeats. When the input voltage ramps up too slowly, slight over- current at the input can occur. Connecting a small capacitor at EN will delay the start-up. The delay time TD can be calculated by: where: •CEN is the capacitance at EN pin •VEN_HI is the EN input high level (function of VDD voltage, see Figure 5) •IEN is the EN pin pull-up current, nominal 2.5µA If a slower than 2ms soft start-up is needed, please refer to Full Start-Up Control section. Steady-State Operation The converter always operates at fixed frequency continuous-conduction mode. For fast transient response, peak current control method is employed. The inductor current is sensed from the upper PFET. This current signal, the slope compensation, and the compensated error signal are fed to the PWM comparator to generate the PWM signal for the internal power switches. When the upper PFET is on, the low-side NFET is off and input voltage charges the inductor. When PFET is off, the NFET is on and energy stored in the inductor is dumped to the output to maintain constant output voltage. Therefore, the LX waveform is always a stable square waveform (see Figure 13) with peak close to VIN. So LX is a good indication that the converter is operating properly. 100% Duty Ratio EL7554 uses CMOS as internal synchronous power switches. The upper switch is a PMOS and the lower switch an NMOS. This not only saves a boot capacitor, it also allows 100% turn-on of the upper PFET switch, achieving FIGURE 18. ADJUSTABLE START-UP FIGURE 19. TRACKING START-UP Waveforms (Continued) VIN = VD = 3.3V, VO = 1.8V, IO = 4A, L = 2.2µH, CIN = 2x10µF, COUT = 47µF, COSC = 220pF, TA = 25°C unless otherwise noted. VIN (2V/DIV) IIN (2A/DIV) VO (1V/DIV) 2ms/DIV CIN = 100µF, COUT = 150µF VIN (5V/DIV) VO1=2.5V VO2=1.8V 5ms/DIV CIN = 100µF, COUT = 150µF TD CEN VEN_HI IEN -------------------- × = EL7554 |
Similar Part No. - EL7554IREZ-T7 |
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Similar Description - EL7554IREZ-T7 |
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