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DDC232CGXGR Datasheet(数据表) 15 Page  Texas Instruments 


DDC232CGXGR Datasheet(HTML) 15 Page  Texas Instruments 
15 page Int A/Meas B Cont 5 CONV • mbsy CONV • mbsy State Diagram Notation: CONV • mbsy = CONV high AND mbsy active. CONVmbsy = CONV high OR mbsy active. CONV • mbsy CONV • mbsy CONV • mbsy CONV • mbsy CONV CONV Int B/Meas A Cont 4 Ncont 1 Ncont 2 Int A Cont 3 Ncont 8 Ncont 7 Int B Cont 6 CONV CONV CONVmbsy CONVmbsy DDC232 www.ti.com SBAS331D – AUGUST 2004 – REVISED APRIL 2010 Continuous and Noncontinuous Operational Four signals are used to control progression around Modes the state diagram: CONV, mbsy, and their complements. The state machine uses the level as Figure 10 shows the state diagram of the DDC232. In opposed to the edges of CONV to control the all, there are eight states. Table 8 provides a brief progression. mbsy is an internallygenerated signal explanation of each state. not available to the user. It is active whenever a measurement/reset/autozero (m/r/az) cycle is in progress. During the Continuous (Cont) mode, mbsy is not active when CONV toggles. The nonintegrating side is always ready to begin integrating when the other side finishes its integration. Consequently, monitoring the current status of CONV is all that is needed to know the current state. Cont mode operation corresponds to states 3 to 6. Two of the states, 3 and 6, only perform an integration (that is, no m/r/az cycle). mbsy becomes important when operating in the Noncontinuous (Ncont) mode (states 1, 2, 7, and 8). Whenever CONV is toggled while mbsy is active, the DDC232 will enter or remain in either Ncont state 1 (or 8). After mbsy goes inactive, state 2 (or 7) is entered. This state prepares the appropriate side for integration. In the Ncont states, the inputs to the DDC232 are grounded. One interesting observation from the state diagram is that the integrations always alternate between sides A and B. This relationship holds for any CONV pattern and is independent of the mode. States 2 and 7 ensure this relationship during the Ncont mode. When power is first applied to the DDC232, the beginning state is either 1 or 8, depending on the initial level of CONV. For CONV held high at powerup, the beginning state is 1. Conversely, for CONV held low at powerup, the beginning state is 8. In general, there is a symmetry in the state diagram between states 1–8, 2–7, 3–6, and 4–5. Inverting CONV results in the states progressing through their Figure 10. Integrate/Measure State Diagram symmetrical match. Table 8. State Descriptions STATE MODE DESCRIPTION Complete m/r/az of side A, then side B (if previous state is state 4). Initial powerup state 1 Ncont when CONV is initially held high. 2 Ncont Prepare side A for integration. 3 Cont Integrate on side A. 4 Cont Integrate on side B; m/r/az on side A. 5 Cont Integrate on side A; m/r/az on side B. 6 Cont Integrate on side B. 7 Ncont Prepare side B for integration. Complete m/r/az of side B, then side A (if previous state is state 5). Initial powerup state 8 Ncont when CONV is initially held low. Copyright © 2004–2010, Texas Instruments Incorporated Submit Documentation Feedback 15 Product Folder Link(s): DDC232 
