SJA1000 datasheet

Back to back MOSFET, Q1-A and Q1-B have received the V (IN1) (5V) power supply, while Q3-A and Q3-B receives V (IN2) (3.3V) power supply. Use back to back because the MOSFET, the internal diode to prevent the 5V and 3.3V power supply with short circuit. The Gate1 LTC1645 pin control Q3-A and Q3-B, Gate2 pin control Q1-A and Q1-B. ON pin Gate1 conduction threshold voltage of 0.8V, on Gate2 conduction threshold voltage of 2.0V. V (CC1), and V (CC2) pin under-voltage lockout threshold was 2.3V, and 1.2V. Because the circuit is shown in Figure 1, two power supply voltages, so there may occur the following two situations: ? Figure 1: LTC1645 and SJA1000 (using SEPIC converter) constitute the 3.3V and 5V hot swap circuit - Case 1: providing 5V and 3.3V power supply - When the 5V and 3.3V supply voltage were added to V (IN1) and V (IN2) when, D1 to V (CC1), V (CC2), Sense1 and Sense2 pin pulled about 4.7V, is used to remove V (CC1) and V (CC2) of the undervoltage lockout threshold. COMP (+) pin is composed of voltage divider R2 and R6 pulled 2.5V. Because COMP (+) pin voltage (internal comparator inverting input) than the threshold voltage of 1.24V high, so COMPOUT pin (open-drain comparator output) is R7 pulled 5V. This gives the Q5 turns on, and Q3-A and Q3-B of the gate down to the ground. ON pin is R1, R4 and R8 pulled around 2.74V. In a working cycle (t = C2 �� 1.24V/2��A), the internal 10��A from the charge pump power source received Gate1 and Gate2 pin. Gate1 down to the ground pin is Q5, and Gate2 pin voltage begins to rise, the slope of the provisions of the dV / dt = 10��A/C1. Internal charge pump guarantees Gate2 pin voltage rises to about 12V. When Gate2 pin up to 1V or so, Q1-A and Q1-B began to turn, and V (OUT_HOT_SWAP) started to rise. Output voltage will steadily increase the input voltage, here is 5V. Figure 2 shows the Gate2 respectively, and V (OUT_HOT_SWAP) pin voltage up to 12V and 5V respectively, when the characteristic curve.