Datasheet LT1389 (Analog Devices) - 9
| Hersteller | Analog Devices |
| Beschreibung | Nanopower Precision Shunt Voltage Reference |
| Seiten / Seite | 12 / 9 — APPLICATIO S I FOR ATIO. Figure 1. Adjustable Output Voltage Reference. … |
| Dateiformat / Größe | PDF / 219 Kb |
| Dokumentensprache | Englisch |
APPLICATIO S I FOR ATIO. Figure 1. Adjustable Output Voltage Reference. Figure 2. Guard Ring to Reduce Board Leakage
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LT1389
U U W U APPLICATIO S I FOR ATIO
The reverse characteristics of the LT1389 resembles a Board leakage is a concern for a nanopower precision simple resistor Zener diode parallel connection. This well shunt voltage reference. The LT1389 requires attention to behaved characteristic is important to the proper opera- detail in board layout in order to maximize its perfor- tion of circuits like Figure 1. The adjustable output voltage mance. 1.5GΩ of leakage between a DNC pin and a 5V reference depends upon positive feedback from the supply will conduct 2.5nA which induces a 0.2% error in LT1495’s output to start-up and regulate the bias current VOUT. Board leakage can be minimized by encircling the for the LT1389. The LT1389 has no negative resistance DNC pins with a guard ring operated at a potential of VOUT. regions that can interfere with the proper start-up of the By tying the guard ring to VOUT as shown in Figure 2, buffered reference. leakage paths are eliminated. VIN ≥ 10.5V V R OUT – 1.25V B = 0.8µA + V LT1495 OUT LT1389-1.25 1.5V TO 10V – R1 249k TO 8.66M R2 1.24M 1389 F01
Figure 1. Adjustable Output Voltage Reference
BOARD METAL TRACE DNC 1 8 DNC DNC 2 7 DNC LT1389 DNC 3 6 VOUT GND 4 5 GND 1389 F02
Figure 2. Guard Ring to Reduce Board Leakage
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U U W U APPLICATIO S I FOR ATIO
The reverse characteristics of the LT1389 resembles a Board leakage is a concern for a nanopower precision simple resistor Zener diode parallel connection. This well shunt voltage reference. The LT1389 requires attention to behaved characteristic is important to the proper opera- detail in board layout in order to maximize its perfor- tion of circuits like Figure 1. The adjustable output voltage mance. 1.5GΩ of leakage between a DNC pin and a 5V reference depends upon positive feedback from the supply will conduct 2.5nA which induces a 0.2% error in LT1495’s output to start-up and regulate the bias current VOUT. Board leakage can be minimized by encircling the for the LT1389. The LT1389 has no negative resistance DNC pins with a guard ring operated at a potential of VOUT. regions that can interfere with the proper start-up of the By tying the guard ring to VOUT as shown in Figure 2, buffered reference. leakage paths are eliminated. VIN ≥ 10.5V V R OUT – 1.25V B = 0.8µA + V LT1495 OUT LT1389-1.25 1.5V TO 10V – R1 249k TO 8.66M R2 1.24M 1389 F01
Figure 1. Adjustable Output Voltage Reference
BOARD METAL TRACE DNC 1 8 DNC DNC 2 7 DNC LT1389 DNC 3 6 VOUT GND 4 5 GND 1389 F02
Figure 2. Guard Ring to Reduce Board Leakage
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