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EL7566DREZ-T13 Datasheet(PDF) 9 Page - Intersil Corporation |
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EL7566DREZ-T13 Datasheet(HTML) 9 Page - Intersil Corporation |
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9 / 14 page  9 FN7102.7 May 8, 2006 Detailed Description The EL7566 is a 6A capable buck regulator operating from an input voltage range of 3V to 6V. The duty cycle can be adjusted from 0% to 100% allowing for a wide range of programmable output voltages. Patented on-chip resistorless current-sensing enables current mode control for excellent step load response. Overcurrent, Overvoltage, input Undervoltage, and thermal protection is integrated along with soft-start and power-up sequencing features to produce an overall robust power solution for general purpose applications. EL7566DRE vs. EL7566AIRE The EL7566AIRE includes the following feature changes from the EL7566DRE: • Up to 6A Current Sinking Capability • Expanded Temperature Range: -40oC to 85oC • No Overvoltage Protection Start-Up The EL7566 employs a digital soft-start feature to suppress the in-rush current needed to charge the output capacitance and smoothly ramp the output voltage to regulation (See Figure 12). The normal start-up process begins when the input voltage reaches the rising POR threshold (~2.8V) and EN pin is transitioned HIGH by an internal 2.5µA current source. The output voltage is then digitally ramped to regulation over a 2ms period. The 2ms soft start-up time can be extended if needed by configuring the STP and STN pins. (refer to Full Start-Up Control section). If the input voltage is ramped slowly, soft-start may be initiated before the input supply has reached regulation. The lower input voltage will have increased current demand during start-up and may risk an overcurrent event. To prevent such an event from occurring, a capacitor can be placed from the EN pin to GND to program a delay between when the rising POR threshold for VIN is met and when soft- start begins. The programmable delay time, TD, is governed by Equation 1. 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 Steady-State Operation Under all steady-state conditions the converter will operate in fixed frequency continuous-conduction mode. For fast transient response and ease of controllability, a peak current-mode control method is employed. The inductor current is sensed from the upper PMOS. This current signal serves as the ramp to the PWM comparator and is compared against the difference signal generated by the transconductance error amplifier. Slope compensation for the ramp is used to allow for 100% duty cycle operation (see Figure 20). The pulse-width modulated square wave output of the PWM comparator is amplified and serves as the gate drive signals for the switching power FETs. 100% DUTY RATIO EL7566 uses CMOS as internal synchronous power switches. The upper and lower switches are PMOS and NMOS respectively. The upper PMOS saves the need for a boot capacitor normally seen in NMOS/NMOS half-bridges. FIGURE 18. ADJUSTABLE START-UP FIGURE 19. TRACKING START-UP Waveforms VIN = VD = 5V, VO = 2.5V, IO = 6A, fS = 500kHz, L = 2.7µH, CIN = 100µF, COUT = 150µF, TA = 25°C unless otherwise noted. (Continued) VIN (5V/DIV) IIN (2A/DIV) VO (2V/DIV) PG 5ms/DIV VIN (5V/DIV) VO1=2.5V VO2=1.8V 5ms/DIV TD CEN VEN_HI IEN -------------------- × = EL7566 |
Similar Part No. - EL7566DREZ-T13 |
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Similar Description - EL7566DREZ-T13 |
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