Rainbow Electronics MAX5958 - Manual (Page 13)

MAX5957/MAX5958
Triple PCI Express, Hot-Plug Controllers
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Pin Description (continued)
PIN NAME FUNCTION
41 3.3SA+
Slot A 3.3V Positive Current-Sense Input. Connect the positive side of the current-sense resistor to
3.3SA+ using the Kelvin-sensing technique to ensure accurate current sensing.
42 3.3SA-
Slot A 3.3V Negative Current-Sense Input. Connect to the negative side of the sense resistor using
the Kelvin-sensing technique to ensure accurate current sensing.
43 3.3GA
Slot A 3.3V Gate-Drive Output. Connect 3.3GA to the gate of slot A’ s 3.3V MOSFET. At power-up,
V
3.3GA is charged to 5.5V above the 3.3V supply by a constant current derived from V 12VIN .
V 3.3GA ‘s rise time is determined by the external gate capacitance.
44 FAULTA
Open-Drain Fault Output Signal. FAULTA latches active low whenever slot A outputs are shut down
due to a fault. A fault is either of:
• An overcurrent condition lasting longer than the overcurrent timeout.
• A device overtemperature condition.
If the fault is detected in the main outputs, FAULTA must be reset by toggling the ONA input. If the
fault is in the auxiliary output, FAULTA must be reset by toggling both ONA and AUXONA. For the
autorestart version, FAULTA is reset when the part initiates the next power-on cycle.
45 PWRGDA
Open-Drain Power-Good Output. PWRGDA goes low 160ms after all outputs of slot A reach their
final value and the power MOSFETs are fully enhanced.
47 3.3AUXOA Slot A 3.3V Auxiliary Power-Supply Output
50 3.3AUXOB Slot B 3.3V Auxiliary Power-Supply Output
51 PWRGDB
Open-Drain Power-Good Output. PWRGDB goes low 160ms after all outputs of slot B reach their
final value and the power MOSFETs are fully enhanced.
52 FAULTB
Open-Drain Fault Output Signal. FAULTB latches active low whenever the slot B outputs are shut
down due to a fault. A fault is either of:
• An overcurrent condition lasting longer than the overcurrent timeout.
• A device over temperature condition.
If the fault is detected in the main outputs, FAULTB must be reset by toggling the ONB input. If the
fault is in the auxiliary output, FAULTB must be reset by toggling both ONB and AUXONB. For the
autorestart version, FAULTB is reset when the part initiates the next power-on cycle.
53 3.3GB
Slot B 3.3V Gate-Drive Output. Connect 3.3GB to the gate of slot B’s 3.3V MOSFET. At power-up,
V
3.3GB is charged to 5.5V above the 3.3V supply by a constant current derived from V 12VIN .
V 3.3GB ‘s rise time is determined by the external gate capacitance.
54 3.3SB-
Slot B 3.3V Negative Current-Sense Input. Connect to the negative side of the sense resistor using
the Kelvin-sensing technique to ensure accurate current sensing.
55 3.3SB+
Slot B 3.3V Positive Current-Sense Input. Connect the positive side of the current-sense resistor to
3.3SB+ using the Kelvin-sensing technique to ensure accurate current sensing.
56 12GB
Slot B 12V Gate-Drive Output. Connect 12GB to the gate of slot B’s 12V MOSFET. At power-up,
V
12GB is raised to the internal charge-pump voltage level by a constant current.
Detailed Description
The MAX5957/MAX5958 triple hot-plug controllers are
designed for PCIe applications. The devices provide
hot-plug control for 12V, 3.3V, and 3.3V auxiliary sup-
plies for three PCIe slots. The MAX5957/MAX5958s’
logic inputs/outputs allow interfacing directly with the
system hot-plug-management controller or through an
SMBus with an external I/O expander. An integrated
debounced attention switch and present-detect signals
are included to simplify system design (Figure 1).
The MAX5957/MAX5958 drive six external n-channel
MOSFETs to control the 12V and 3.3V main outputs.
The 3.3V auxiliary outputs are controlled through inter-
nal 0.2Ω n-channel MOSFETs. Internal charge pumps
provide a gate drive for the 12V outputs while the gate
drive of the 3.3V output is driven by the 12V input sup-
ply. The 3.3V auxiliary outputs are completely indepen-
dent from the main outputs with their own charge
pumps.