 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
TPS71257 Datasheet(PDF) 9 Page - Texas Instruments |
|
||||||||||||||||||||||||||||||
TPS71257 Datasheet(HTML) 9 Page - Texas Instruments |
|
|
9 / 15 page  www.ti.com APPLICATION INFORMATION OUTPUT NOISE TPS712xx GND EN2 NR IN OUT1 EN1 OUT2 V IN V OUT1 V OUT2 0.1 µF 2.2 µF 2.2 µF 0.01 µF INPUT AND OUTPUT CAPACITOR STARTUP CHARACTERISITCS TPS71202, TPS71219 TPS71229, TPS71247 TPS71256, TPS71257 SBVS049B – MAY 2004 – REVISED MARCH 2005 1.8 V or less is chosen, the minimum recommended The TPS712xx family of dual low-dropout (LDO) output capacitor is 4.7 µF. Any ceramic capacitor that regulators has been optimized for use in meets the minimum output capacitor requirements is noise-sensitive battery-operated equipment. The de- suitable. Capacitors with higher ESR may be used, vice features extremely low dropout, high PSRR, provided the ESR is less than 1 Ω. ultralow output noise, and low quiescent current (190 µA typical per channel). When both outputs are disabled, the supply currents are reduced to less than 2µA. A typical application circuit is shown in Fig- The internal voltage reference is a key source of ure 24. noise in an LDO regulator. The TPS712xx has an NR pin that is connected to the voltage reference through a 250 k Ω internal resistor. The 250 kΩ internal resistor, in conjunction with an external ceramic bypass capacitor connected to the NR pin, creates a low-pass filter to reduce the voltage reference noise and, therefore, the noise at the regulator output. To achieve a fast startup, the 250 k Ω internal resistor is shorted for 400 µs after the device is enabled. Because the primary noise source is the internal voltage reference, the output noise will be greater for higher output voltage versions. For the case where no noise reduction capacitor is used, the typical noise Figure 24. Typical Application Circuit (µVrms) over 10 Hz to 100 kHz is 80 times the output (fixed-voltage versions) voltage. If a 0.01 µF capacitor is used from the NR pin to ground, the noise (µVrms) drops to 11.8 times the output voltage. For example, the TPS71256 exhibits only 33 µVrms of output voltage noise using REQUIREMENTS a 0.01 µF ceramic bypass capacitor and a 2.2 µF ceramic output capacitor. A 0.1 µF or larger ceramic input bypass capacitor, connected between IN and GND and located close to the TPS712xx, is required for stability. It improves transient response, noise rejection, and ripple rejec- To minimize startup overshoot, the TPS712xx will tion. A higher-value input capacitor may be necessary initially target an output voltage that is approximately if large, fast-rise-time load transients are anticipated 80% of the final value. To avoid a delayed startup and the device is located several inches from the time, noise reduction capacitors of 0.01 µF or less power source. are recommended. Larger noise reduction capacitors The TPS712xx requires an output capacitor connec- will cause the output to hold at 80% until the voltage ted between the outputs and GND to stabilize the on the noise reduction capacitor exceeds 80% of the internal control loops. The minimum recommended bandgap voltage. The typical startup time with a output capacitor is 2.2 µF. If an output voltage of 0.001 µF noise reduction capacitor is 60 µs. Once one of the output voltages is present, the startup time of the other output will not be affected by the noise reduction capacitor. 9 |
Similar Part No. - TPS71257 |
|
Similar Description - TPS71257 |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.NET |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
