Datasheet LM4041 (Diodes) - 5

LM4041 PRECISION MICROPOWER SHUNT VOLTAGE REFERENCES Application Information
In a conventional shunt regulator application (Figure 1), an VS external series resistor (RS) is connected between the supply voltage, VS, and the LM4041. IR + IL VS RS I IR + L VO I L RS I L IR V R VR IR Figure 2 Figure 1 RS determines the current that flows through the load (IL) The LM4041-ADJ’s output voltage can be adjusted to any and the LM4041 (IR). Since load current and supply value in the range of 1.24V through 10V. The output voltage may vary, RS should be small enough to supply at voltage is set by the ratio of two external feedback least the minimum acceptable IR to the LM4040 even resistors as shown in Figure 2 and the internal reference when the supply voltage is at its minimum and the load voltage (VR). current is at its maximum value. When the supply voltage The output voltage is found using the equation: is at its maximum and IL is at its minimum, RS should be ⎛ R ⎞ large enough so that the current flowing through the V = V × 2 O R ⎜⎜1+ ⎟⎟ LM4040 is less than 12 mA. ⎝ 1 R ⎠ RS is determined by the supply voltage, (VS), the load and operating current, (IL and IQ), and the LM4040’s reverse
Printed circuit board layout considerations
breakdown voltage, VR. LM4041 with fixed output voltage in the SOT23 package has the die attached to pin 1, which results in an electrical contact between pin 2 and pin 1. Therefore, pin 1 of the S V − R V RS = SOT23 package must be left floating or connected to L I + R I pin 2. The LM4041 comes in two varients: LM4041 with fixed output voltage in the SC70-5 package • LM4041 with fixed 1.225V output have the die attached to pin 2, which results in an • LM4041_ADJ with variable output voltage. electrical contact between pin 2 and pin 1. Therefore, pin 2 must be left floating or connected to pin1. LM4041 5 of 7 September 2011 Document number: DS32020 Rev. 8 - 2
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