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TC1054 Datasheet(PDF) 10 Page - TelCom Semiconductor, Inc |
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TC1054 Datasheet(HTML) 10 Page - TelCom Semiconductor, Inc |
10 / 12 page TC1055 100mA CMOS LDO WITH SHUTDOWN AND ERROR OUTPUT 4 PRELIMINARY INFORMATION TC1055-01 6/5/97 DETAILED DESCRIPTION The TC1055 is a precision fixed output voltage regula- tor. (If an adjustable version is desired, please see the TC1070 or TC1071 data sheets.) Unlike the bipolar regula- tors, the TC1055 supply current does not increase with load current. In addition, VOUT remains stable and within regula- tion at very low load currents (an important consideration in RTC and CMOS RAM battery back-up applications). Figure 1 shows a typical application circuit. The regula- tor is enabled any time the shutdown input (SHDN) is at or above 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) and VOUT falls to zero volts and ERROR is open circuited. ERROR Open Drain Output ERROR is driven low whenever VOUT falls out of regu- lation by more than – 5% (typical). This condition may be caused by low input voltage, output current limiting, or thermal limiting. The ERROR threshold is 5% below rated VOUT regardless of the programmed output voltage value (e.g. ERROR = VOL at 4.75 (typ.) for a 5.0V regulator and 2.85V (typ.) for a 3.0V regulator). ERROR output operation is shown in Figure 2. Note that ERROR is active when VOUT falls to VTH, and inactive when VOUT rises above VTH by VHYS. As shown in Figure 1, ERROR can be used as a battery low flag, or as a processor RESET signal (with the addition of timing capacitor C2). R1 x C2 should be chosen to maintain ERROR below VIH of the processor RESET input for at least 200msec to allow time for the system to stabilize. Pull-up resistor R1 can be tied to VOUT, VIN or any other voltage less than (VIN + 0.3V). Output Capacitor A 1 µF(min) capacitor from VOUT to ground is recom- mended. The output capacitor should have an effective series resistance of 5 Ω or less, and a resonant frequency above 1MHz. A 1 µF 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 tanta- lum 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 tech- niques. Thermal Considerations Thermal Shutdown Integrated thermal protection circuitry shuts the regula- tor off when die temperature exceeds 160 °C. The regulator remains off until the die temperature drops to approximately 150 °C. Power Dissipation The amount of power the regulator dissipates is prima- rily a function of input and output voltage, and output current. The following equation is used to calculate worst case actual power dissipation: Figure 1. Typical Application Circuit 1 µF C1 0.2 µF C2 R1 1M V+ C2 Requires Only if ERROR is used as a Processor RESET Signal (See Text) Shutdown Control (to CMOS Logic or Tie to V IN if unused) BATTLOW or RESET TC1055VCT VIN BATTERY VOUT ERROR SHDN GND VOUT 1 µF Figure 2. ERROR Output Operation VIH VOL ERROR V TH V OUT HYSTERESIS (V HYS) |
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Descripción similar - TC1054 |
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