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TC1174VOA Datasheet(PDF) 4 Page - Microchip Technology |
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TC1174VOA Datasheet(HTML) 4 Page - Microchip Technology |
4 / 12 page TC1174 DS21363B-page 4 © 2002 Microchip Technology Inc. 3.0 DETAILED DESCRIPTION The TC1174 is an adjustable low drop-out regulator. Unlike bipolar regulators, the TC1174’s supply current does not increase with load current. In addition, VOUT remains stable and within regulation over the entire 0mA to IOUTMAX operating load current range, (an important consideration in RTC and CMOS RAM battery back-up applications). Figure 3-1 shows a typical application circuit. The regulator is enabled any time the shutdown input (SHDN)isatorabove VIH, and shutdown (disabled) when SHDN is at or below VIL. SHDN may be controlled by a CMOS logic gate, or I/O port of a microcontroller. If the SHDN input is not required, it should be connected directly to the input supply. While in shutdown, supply current decreases to 0.05 µA (typical), VOUT falls to zero. FIGURE 3-1: TYPICAL APPLICATION CIRCUIT 3.1 Bypass Input A 470pF capacitor connected from the Bypass input to ground reduces noise present on the internal reference, which in turn significantly reduces output noise. If output noise is not a concern, this input may be left unconnected. Larger capacitor values may be used, but results in a longer time period to rated output voltage when power is initially applied. 3.2 Output Capacitor A1 µF(min) capacitor from VOUT to ground is required. The output capacitor should have an effective series resistance greater than 0.1 Ω and less than 5.0Ω.A 1µF capacitor should be connected from VIN to GND if there is more than 10 inches of wire between the regulator and the AC filter capacitor, or if a battery is used as the power source. Aluminum electrolytic or tantalum capacitor types can be used. (Since many aluminum electrolytic capacitors freeze at approximately -30°C, solid tantalums are recommended for applications operating below -25°C.) When operating from sources other than batteries, supply-noise rejection and transient response can be improved by increasing the value of the input and output capacitors and employing passive filtering techniques. 3.3 Adjust Input The output voltage setting is determined by the values of R1 and R2 (Figure 3-1). The ohmic values of these resistors should be between 470K and 3M to minimize bleeder current. The output voltage setting is calculated using the following equation. EQUATION 3-1: The voltage adjustment range of the TC1174 is from VREF to (VIN –0.05V). TC1174 1 2 3 4 5 6 7 8 VOUT VOUT CBYPASS 470pF (Optional) Shutdown Control (from Power Control Logic) C1 1 µF GND NC ADJ VIN NC Bypass SHDN R1 470K 470K R2 C2 1 µF Battery + + + – VOUT =VREF x [ +1 ] R1 R2 |
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