전자부품 데이터시트 검색엔진 |
|
MC10319 데이터시트(PDF) 10 Page - Motorola, Inc |
|
MC10319 데이터시트(HTML) 10 Page - Motorola, Inc |
10 / 20 page MC10319 10 MOTOROLA ANALOG IC DEVICE DATA APPLICATIONS INFORMATION Power Supplies, Grounding The PC board layout, and the quality of the power supplies and the ground system at the IC are very important in order to obtain proper operation. Noise, from any source, coming into the device on VCC, VEE, or ground can cause an incorrect output code due to interaction with the analog portion of the circuit. At the same time, noise generated within the MC10319 can cause incorrect operation if that noise does not have a clear path to ac ground. Both the VCC and VEE power supplies must be decoupled to ground at the IC (within 1 I max) with a 10 µF tantalum and a 0.1 µF ceramic. Tantalum capacitors are recommended since electrolytic capacitors simply have too much inductance at the frequencies of interest. The quality of the VCC and VEE supplies should then be checked at the IC with a high frequency scope. Noise spikes (always present when digital circuits are present) can easily exceed 400 mV peak, and if they get into the analog portion of the IC, the operation can be disrupted. Noise can be reduced by inserting resistors and/or inductors between the supplies and the IC. If switching power supplies are used, there will usually be spikes of 0.5 V or greater at frequencies of 50 to 200 kHz. These spikes are generally more difficult to reduce because of their greater energy content. In extreme cases, 3–terminal regulators (MC78L05ACP, MC7905.2CT), with appropriate high frequency filtering, should be used and dedicated to the MC10319. The ripple content of the supplies should not allow their magnitude to exceed the values in the Recommended Operating Limits table. The PC board tracks supplying VCC and VEE to the MC10319 should preferably not be at the tail end of the bus distribution, after passing through a maze of digital circuitry. The MC10319 should be close to the power supply, or the connector where the supply voltages enter the board. If the VCC and VEE lines are supplying considerable current to other parts of the boards, then it is preferable to have dedicated lines from the supply or connector directly to the MC10319. The four ground pins (2, 12, 16, and 22) must be connected directly together. Any long path between them can cause stability problems due to the inductance (at 25 MHz) of the PC tracks. The ground return for the signal source must be noise free. Reference Voltage Circuits Since the accuracy of the conversion is directly related to the quality of the references, it is imperative that accurate and stable voltages be provided to VRT and VRB. If the reference span is 2.0 V, then 1/2 LSB is only 3.9 mV, and it is desireable that VRT and VRB be accurate to within this amount, and furthermore, that they do not drift more than this amount once set. Over the temperature range of 0 ° to 70°C, a maximum temperature coefficient of 28 ppm/ °C is required. The voltage supplies used for digital circuits should preferably not be used as a source for generating VRT and VRB, due to the noise spikes (50 to 400 mV) present on the supplies and on their ground lines. Generally ± 15 V, or ±12 V, are available for analog circuits, and are usually clean compared to supplies used for digital circuits, although ripple may be present in varying amounts. Ripple is easier to filter out than spikes, however, and so these supplies are preferred. Figure 21 depicts a circuit which can provide an extremely stable voltage to VRT at the current required (the maximum reference current is 19.2 mA @ 2.0 V). The MC1403 series of reference sources has very low temperature coefficients, good noise rejection, and a high initial accuracy, allowing the circuit to be built without an adjustment pot if the VRT voltage is to remain fixed at one value. Using 0.1% wirewound resistors for the divider provides sufficient accuracy and stability in many cases. Alternately, resistor networks provide high ratio accuracies, and close temperature tracking. If the application requires VRT to be changed periodically, the two resistors can be replaced with a 20 turn, cermet potentiometer. Wirewound potentiometers should not be used for this type of application since the pot’s slider jumps from winding to winding, and an exact setting can be difficult to obtain. Cermet pots allow for a smooth continuous adjustment. In Figure 21, R1 reduces the power dissipation in the transistor, and can be carbon composition. The 0.1 µF capacitor in the feedback path provides stability in the unity gain configuration. Recommended op amps are: LM358, MC34001 series, LM308A, LM324, and LM11C. Offset drift is the key parameter to consider in choosing an op amp, and the LM308A has the lowest drift of those mentioned. Bypass capacitors are not shown in Figure 21, but should always be provided at the input to the 2.5 V reference, and at the power supply pins of the op amp. Figure 22 shows a simpler and more economical circuit, using the LM317LZ regulator, but with lower initial accuracy and temperature stability. The op amp/current booster is not needed since the LM317LZ can supply the current directly. In a well controlled environment, this circuit will suffice for many applications. Because of the lower initial accuracy, an adjustment pot is a necessity. Figure 23 shows two circuits for providing the voltage to VRB. The circuits are similar to those of Figures 21 and 22, and have similar accuracy and stability. The output transistor is a PNP in this case since the circuit must sink the reference current. |
유사한 부품 번호 - MC10319 |
|
유사한 설명 - MC10319 |
|
|
링크 URL |
개인정보취급방침 |
ALLDATASHEET.CO.KR |
ALLDATASHEET 가 귀하에 도움이 되셨나요? [ DONATE ] |
Alldatasheet는? | 광고문의 | 운영자에게 연락하기 | 개인정보취급방침 | 링크교환 | 제조사별 검색 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 |