Datenblatt-Suchmaschine für elektronische Bauteile |
|
ADP1147AN-33 Datenblatt(PDF) 11 Page - Analog Devices |
|
ADP1147AN-33 Datenblatt(HTML) 11 Page - Analog Devices |
11 / 12 page ADP1147-3.3/ADP1147-5 –11– REV. 0 To obtain optimum efficiency the required ESR value of COUT is 100 m Ω or less. The circuit should also be evaluated with the minimum input voltage. This is done to assure that the power dissipation and junction temperature of the P-channel MOSFET are not ex- ceeded. At lower input voltages the operating frequency of the ADP1147 decreases. This causes the P-channel MOSFET to remain in conduction for longer periods of time, resulting in more power dissipation in the MOSFET. The effects of VIN(MIN) can be evaluated if we assume the following: VIN(MIN) = 4.5 V VOUT = 3.3 V VD = 0.4 V fMIN = (1/3.15 µs) × (1– (3.7/4.9)) = 78 kHz. PD = 3.3(0.125 Ω)(1 A)2 (1.2625) 4.5 =116 mW Troubleshooting Hints Efficiency is the primary reason for choosing the ADP1147 for use in an application, and it is critical to determine that all por- tions of the circuit are functioning properly in all modes. After the design is complete the voltage waveforms on the timing capacitor, CT, at Pin 2 of the device, should be compared to the waveforms in Figures 19a and 19b. In the continuous mode of operation the dc voltage level of the waveform on CT should never fall below the 2 V level and it should have a 0.9 V peak-to-peak sawtooth on it (see Figure 19a). In the Power Savings Mode the sawtooth waveform on CT will decay to ground for extended periods of time (see Figure 19b). During the time that the capacitor voltage is at ground the ADP1147 is in the power savings or sleep mode and the qui- escent current is reduced to 160 µA typical. The ripple current in the inductor should also be monitored to determine that it is approximately the same in both modes of operation. With a higher output currents the voltage level on CT should never decay to ground as this would indicate poor grounding and or decoupling. Printed Wire Board Layout Considerations The PWB layout is extremely critical for proper circuit opera- tion and the items listed below should be carefully considered (see Figure 20) 1. The signal and power grounds should be separate from each other. They should be tied together only at ground Pin 7 of the ADP1147. The power ground should be tied to the an- ode of the Schottky diode, and the (–) side of the CIN capaci- tor. The connections should be made with traces that are as wide and as short as possible. The signal ground should be connected to the (–) side of capacitor COUT using the same type of runs as above. 2. The sense(–) run to Pin 4 of the ADP1147 should be con- nected directly to the junction point of RSENSE and the + side of COUT. 3. The sense(–) and sense(+) traces should be routed together with minimum track spacing and run lengths. The 1000 pF filter capacitor across Pins 4 and 5 of the ADP1147 should be located as close to the device as possible. 4. In order to supply sufficient ac current the (+) side of capaci- tor CIN should be connected with wide short traces and must be located as close to the source of the P-MOSFET as possible. 5. In order to supply high frequency peak currents the input decoupling capacitors should range from 0.1 µF to 1.0 µF and must be located as close to the VIN pin and the ground Pin 7 as possible. 6. The shutdown Pin (6) is a high impedance input and it must not be allowed to float. The normal mode of operation of the device requires that this pin be pulled low. |
Ähnliche Teilenummer - ADP1147AN-33 |
|
Ähnliche Beschreibung - ADP1147AN-33 |
|
|
Link URL |
Privatsphäre und Datenschutz |
ALLDATASHEETDE.COM |
War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Linktausch | Hersteller 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 |