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ISL45042IRZ-T Fiches technique(PDF) 6 Page - Intersil Corporation |
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ISL45042IRZ-T Fiches technique(HTML) 6 Page - Intersil Corporation |
6 / 8 page 6 FN6072.6 November 14, 2006 Table 1 gives the calculated value of VOUT for resistors values of: RSET = 24.9kΩ, R1 = 200kΩ, R2 = 243kΩ, and VADD = 10V. RSET Resistor The external RSET resistor sets the full-scale sink current that determines the lowest voltage of the external voltage divider R1 and R2 (Figure 1). The maximum ISET current has to be less than 120 μA. The minimum RSET resistor with AVDD equal to 10V is 4.17kΩ (10V/(20*120μA). Typical applications with AVDD equal to 10V and RSET equal to 24.9k Ω will result in a set current equal to 20μA. Power Supply Sequence The recommendation for power supply sequence would be to power down the part first (Vdd, AVdd), after 100msec if programming has occurred, and then power down the control power supplies (CTL, CE). Verifying the Programmed Value The following sequence can be used to verify the programmed value without having to sequence the VDD supply. To verify the programmed value, follow the steps below. The ISL45042 will read memory contents and be set to that value when the CE pin is grounded. 1. Power up the ISL45042. 2. CE pin = VDD. 3. Change counter value with CTL pin to desired value. 4. CTL = more than 4.9V and 200msec. Counter value programmed. 5. Change the counter value with CTL pin to a different value. 6. CE pin = Ground. 7. Check that the output value is the one programmed in step #4. Generating VDD and CE supply from a Larger Voltage Source The CE pin has an internal pull-down resistor (RINTERNAL Figure 5). The impedance of this resistor is 400k Ω-500kΩ. If your design is using a resistor divider network to generate the 3.3V supply (for both VDD and CE to enable programming) from a larger voltage source, the 400k Ω (worst case) resistor needs to be taken into account as a parallel resistance when the CE pin is connected to this source. Another design concern is to be able to provide enough supply current during programming. The ISL45042 draws about 2mA during this process. Recommended resistor values are shown in Figure 5. This design will result in an additional 0.83mA quiescent current flowing through resistors RA and RB.. ISL45042 Truth Table The ISL45042 truth table is shown in Table 2. For proper operation the CE should be disabled (pulled low) before powering the device down to assure that the glitches and transients will not cause unwanted EEPROM overwriting. TABLE 1. CALCULATED VCOM OUTPUT VOLTAGES SETTING VALUE VOUT 1 5.468 10 5.313 20 5.141 30 4.969 40 4.797 50 4.625 60 4.453 70 4.281 80 4.109 90 3.936 100 3.764 110 3.592 128 3.282 TABLE 2. TRUTH TABLE INPUT OUTPUT CTL CE VDD OUT ICC MEMORY Mid to Hi Hi VDD Increment Normal X Mid to Lo Hi VDD Decrement Normal X X Lo VDD No Change Increased Read >4.9V Hi VDD No Change Increased Program FIGURE 5. APPLICATION GENERATING VDD AND VCE VOLTAGES VCC= 5V CE LOGIC RINTERNAL = 400kΩ to 500kΩ RA RB 2k Ω 4k Ω ISL45042 CE VCE ISL45042 |
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Description similaire - ISL45042IRZ-T |
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