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LM4120AIM5X-4.1 Datasheet(PDF) 9 Page - National Semiconductor (TI) |
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LM4120AIM5X-4.1 Datasheet(HTML) 9 Page - National Semiconductor (TI) |
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9 / 12 page  LM4120 Typical Operating Characteristics Unless otherwise specified, V IN = 3.3V, VOUT = 2.5V, ILOAD =0,COUT = 0.022µF, TA = 25˚C and VEN =VIN. (Continued) Thermal Hysteresis Enable Pin Current 10104731 10104716 Pin Functions Output (Pin 5): Reference Output. Input (Pin 4):Positive Supply. Ground (Pin 2):Negative Supply or Ground Connection. Enable (Pin 3):Pulled to input for normal operation. Forcing this pin to ground will turn-off the output. REF (Pin 1):REF Pin. This pin should be left unconnected. Application Hints The standard application circuit for the LM4120 is shown in Figure 1. It is designed to be stable with ceramic output capacitors in the range of 0.022µF to 0.047µF. Note that 0.022µF is the minimum required output capacitor. These capacitors typically have an ESR of about 0.1 to 0.5 Ω. Smaller ESR can be tolerated, however larger ESR can not. The output capacitor can be increased to improve load tran- sient response, up to about 1µF. However, values above 0.047µF must be tantalum. With tantalum capacitors, in the 1µF range, a small capacitor between the output and the reference pin is required. This capacitor will typically be in the 50pF range. Care must be taken when using output capacitors of 1µF or larger. These application must be thor- oughly tested over temperature, line and load. An input capacitor is typically not required. However, a 0.1µF ceramic can be used to help prevent line transients from entering the LM4120. Larger input capacitors should be tantalum or aluminium. The reference pin is sensitive to noise, and capacitive load- ing. Therefore, the PCB layout should isolate this pin as much as possible. The enable pin is an analog input with very little hysteresis. About 6µA into this pin is required to turn the part on, and it must be taken close to GND to turn the part off (see spec. table for thresholds). There is a minimum slew rate on this pin of about 0.003V/µS to prevent glitches on the output. All of these conditions can easily be met with ordinary CMOS or TTL logic. If the shutdown feature is not required, then this pin can safely be connected directly to the input supply. Floating this pin is not recommended. INPUT CAPACITOR Noise on the power-supply input can effect the output noise, but can be reduced by using an optional bypass capacitor between the input pin and the ground. PRINTED CIRCUIT BOARD LAYOUT CONSIDERATION The mechanical stress due to PC board mounting can cause the output voltage to shift from its initial value. References in SOT packages are generally less prone to assembly stress than devices in Small Outline (SOIC) package. To reduce the stress-related output voltage shifts, mount the reference on the low flex areas of the PC board such as near to the edge or the corner of the PC board. 10104732 FIGURE 1. www.national.com 9 |
Número de pieza similar - LM4120AIM5X-4.1 |
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Descripción similar - LM4120AIM5X-4.1 |
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