3 Bench Test

After adding the proposed circuit, the startup waveform is shown in Figure 3-1.

• When the V_IN is lower than 1.7 V, the TPS61022 device shuts down. The VOUT is zero and the EN pin voltage is equal to the input voltage.
• After V_IN > 1.7 V, the TPS61022 device starts to operate. The VOUT ramps up to 5 V. Then Q1 turns on and the EN pin voltage decreases to 0.6 V. If the V_EN is still higher than the EN pin logic low threshold, the device keeps operating.

Figure 3-1 Startup After Adding Proposed Circuit

The Figure 3-2 shows the shutdown waveform at 1-mA load condition as the V_IN deceases. As the V_IN decreases toward 1.2 V, the EN also decreases toward 0.42 V. Once the EN pin voltage is lower than 0.42 V, the device stops operating and V_OUT decreases. After V_OUT decreases below approximately 2.4 V, Q1 turns off and the V_EN becomes equal to VIN again. The VIN is lower than 1.7 V, so the device does not restart, although the EN pin becomes logic high again.

Figure 3-2 Shutdown at 1-mA Condition

Figure 3-3 shows the shutdown waveform at the 500-mA load condition. The boost converter shuts down when V_IN is lower than 1.2 V as designed. Because of the voltage drop across the input cable, the input voltage increases 100 mV after device shuts down.

Figure 3-3 Shutdown at 500-mA Load