5-channel (3 +V and 2 -V) hot-swap reference design

introduction

Although the 5-channel circuit introduced in this article only uses a MAX5927A 4-channel hot-swappable controller, it can realize the hot-swappable function of 3 positive power supplies and 2 negative power supplies. The circuit in Figure 1 meets the following load power supply and power-on sequencing requirements:

• At 2A, Ch1 = +3.3V (circuit is powered off at ≥ 3A)

• At 1.6A, Ch2 = +5V (circuit is powered off at ≥ 2.4A)

• At 2A, Ch3 = +12V (circuit is powered off at ≥ 3A)

• At 150mA, Ch4 = -12V (no circuit power-off action)

• At 50mA, Ch5 = -5V (no circuit power-off action)

• The startup sequence is: Channel 2 (+5V) and Channel 3 (+12V) are turned on immediately when the active low CARD_PRESENT becomes low. STAT2 and STAT3 become high level 10.8ms after the low-level active CARD_PRESENT becomes low level.

• Channel 1 (+3.3V) turns on with a delay of 11.8ms relative to Channel 2 and Channel 3. 10.8ms after channel 1 is turned on, STAT1 goes high.

• Channel 4 (-12V) and Channel 5 (-5V) turn on with a delay of 27.8ms relative to Channel 2 and Channel 3. 10.8ms after channel 4 and channel 5 are connected, STAT4 becomes high level.

• Latch fault management. If an error occurs in any one of Channel 1 to Channel 3, all channels will be turned off until the active low CARD_PRESENT enters the next off and on cycle.

Figure 1. 5-channel hot-swap circuit controls 3 positive supplies and 2 negative supplies