Datenblatt-Suchmaschine für elektronische Bauteile |
|
CS8121YTFVA5 Datenblatt(PDF) 6 Page - Cherry Semiconductor Corporation |
|
CS8121YTFVA5 Datenblatt(HTML) 6 Page - Cherry Semiconductor Corporation |
6 / 8 page The circuit depicted in Figure 5 lets the microprocessor control its power source, the CS8121 regulator. An I/O port on the µP and the SWITCH port are used to drive the base of Q1. When Q1 is driven into saturation, the voltage on the lead falls below its lower threshold and the regulatorÕs output is switched on. When the drive cur- rent is removed, the voltage on the lead rises, the output is switched off and the IC moves into Sleep mode where it typically draws 250µA. By coupling these two controls with , the system has added flexibility. Once the system is running, the state of the SWITCH is irrelevant as long as the I/O port continues to drive Q1. The µP can turn off its own power by withdrawing drive current, once the SWITCH is open. This software control at the I/O port allows the µP to fin- ish key housekeeping functions before power is removed. The logic options are summarized in Table 1 below The I/O port of the µP typically provides 50 µA to Q1. In automotive applications the SWITCH is connected to the ignition switch. The output or compensation capacitor C2 helps determine three main characteristics of a linear regulator: start-up delay, load transient response and loop stability. The capacitor value and type should be based on cost, availability, size and temperature constraints. A tantalum or aluminum electrolytic capacitor is best, since a film or ceramic capacitor with almost zero ESR can cause insta- bility. The aluminum electrolytic capacitor is the least expensive solution, but, if the circuit operates at low temperatures (-25¡C to -40¡C), both the value and ESR of the capacitor will vary considerably. The capacitor manu- facturers data sheet usually provides this information. The value for the output capacitor C2 shown in the test and applications circuit should work for most applica- tions, however it is not necessarily the optimized solu- tion. To determine an acceptable value for C2 for a particular application, start with a tantalum capacitor of the recom- mended value and work towards a less expensive alterna- tive part. Step 1: Place the completed circuit with a tantalum capacitor of the recommended value in an environmental chamber at the lowest specified operating temperature and monitor the outputs with an oscilloscope. A decade box connected in series with the capacitor will simulate the higher ESR of an aluminum capacitor. Leave the decade box outside the chamber, the small resistance added by the longer leads is negligible. Step 2: With the input voltage at its maximum value, increase the load current slowly from zero to full load while observing the output for any oscillations. If no oscillations are observed, the capacitor is large enough to ensure a stable design under steady state conditions. Step 3: Increase the ESR of the capacitor from zero using the decade box and vary the load current until oscillations appear. Record the values of load current and ESR that cause the greatest oscillation. This represents the worst case load conditions for the regulator at low temperature. Step 4 : Maintain the worst case load conditions set in step 3 and vary the input voltage until the oscillations increase. This point represents the worst case input volt- age conditions. Step 5: If the capacitor is adequate, repeat steps 3 and 4 with the next smaller valued capacitor. A smaller capaci- tor will usually cost less and occupy less board space. If the output oscillates within the range of expected operat- ing conditions, repeat steps 3 and 4 with the next larger standard capacitor value. ENABLE ENABLE ENABLE 6 Stability Considerations C1 0.1 mF VIN Gnd RESET CS–8121 VOUT ENABLE 500k W Q1 500k W 100k W 100k W CRST RRST C2 10 mF VCC I/O Port mP VBAT RESET SWITCH Applications Notes Figure 5. Microprocessor control of CS8121 using external switching transistor Q1. Table 1: Logic Control of CS8121 Output µP I/O drive SWITCH Output ON Closed LOW ON Open LOW ON OFF Closed LOW ON Open HIGH OFF ENABLE |
Ähnliche Teilenummer - CS8121YTFVA5 |
|
Ähnliche Beschreibung - CS8121YTFVA5 |
|
|
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 |