Datasheet LT1529, LT1529-3.3, LT1529-5 (Analog Devices) - 10

LT1529 LT1529-3.3/LT1529-5
O U U W U APPLICATI S I FOR ATIO
micropower device and output transient response will be OUTPUT pin of an adjustable device, or the SENSE pin of a function of output capacitance. See the Transient Re- a fixed voltage device, is pulled below ground, with the sponse curves in the Typical Performance Characteristics. input open or grounded, current must be limited to less Larger values of output capacitance will decrease the peak than 5mA. deviations and provide improved output transient re- In circuits where a backup battery is required, several sponse for larger load current deltas. Bypass capacitors, different input/output conditions can occur. The output used to decouple individual components powered by the voltage may be held up while the input is either pulled to LT1529, will increase the effective value of the output ground, pulled to some intermediate voltage, or is left capacitor. open circuit. Current flow back into the output will vary depending on the conditions. Many battery-powered cir-
Protection Features
cuits incorporate some form of power management. The The LT1529 incorporates several protection features which following information will help optimize battery life. Table make it ideal for use in battery-powered circuits. In addi- 2 summarizes the following information. tion to the normal protection features associated with The reverse output current will follow the curve in Figure monolithic regulators, such as current limiting and ther- 3 when the input is pulled to ground. This current flows mal limiting, the device is protected against reverse input through the device to ground. The state of the SHDN pin voltages, and reverse voltages from output to input. will have no effect on output current when the VIN pin is Current limit protection and thermal overload protection pulled to ground. are intended to protect the device against current overload conditions at the output of the device. For normal opera- 100 TJ = 25°C, VIN = 0V tion, the junction temperature should not exceed 125°C. 90 VOUT = VSENSE 80 (LT1529-3.3/LT1529-5) The input of the device will withstand reverse voltages of V A) OUT = VADJ (LT1529) µ 70 CURRENT FLOWS 15V. Current flow into the device will be limited to less than INTO DEVICE 60 1mA (typically less than 100µA) and no negative voltage LT1529 50 will appear at the output. The device will protect both itself 40 and the load. This provides protection against batteries 30 OUTPUT CURRENT ( LT1529-3.3 that can be plugged in backwards. 20 LT1529-5 10 For fixed voltage versions of the device, the SENSE pin is 0 internally clamped to one diode drop below ground. For 0 1 2 3 4 5 6 7 8 9 10 OUTPUT VOLTAGE (V) the adjustable version of the device, the OUTPUT pin is LT1529 • F03 internally clamped at one diode drop below ground. If the
Figure 3. Reverse Output Current Table 2. Fault Conditions VIN PIN SHDN PIN OUTPUT/SENSE PINS
< VOUT (Nominal) Open (High) Forced to VOUT (Nominal) Reverse Output Current ≈ 15µA (See Figure 3), Input Current ≈ 1µA (See Figure 4) < VOUT (Nominal) Grounded Forced to VOUT (Nominal) Reverse Output Current ≈ 15µA (See Figure 3), Input Current ≈ 1µA (See Figure 4) Open Open (High) > 1V Reverse Output Current ≈ 15µA Peak (See Figure 3) Open Grounded > 1V Reverse Output Current ≈ 15µA (See Figure 3) ≤ 0.8V Open (High) ≤ 0V Output Current = 0 ≤ 0.8V Grounded ≤ 0V Output Current = 0 >1.5V Open (High) ≤ 0V Output Current = Short-Circuit Current – 15V < VIN < 15V Grounded ≤0V Output Current = 0 152935fb 10