MAX5954 Datasheet, PDF (12/22 Pages) Maxim Integrated Products – Single PCI Express, Hot-Plug Controller

Single PCI Express, Hot-Plug
Controller
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15–23,
26, 27,
29, 30
24
Pin Description
NAME
PRES-DET
FUNCTION
Present-Detect Input. PRES-DET accepts inputs from the PRSNT#2 pin on a PCI-E connector. PRES-DET
has an internal pullup to 3.3VAUXIN. When PRES-DET is low, the outputs follow the command from ON
and AUXON after a 4ms debounced time. When PRES-DET goes from low to high, all outputs of the
respective slot shut down with no delay (see Table 2).
FON
Forced-On Input. FON has a 50kΩ internal pullup to 3.3VAUXIN. A logic-low on FON turns on all PCI-E
outputs as long as the power inputs are within their operating range, regardless of the status of the other
input signals. Leave FON open for normal operation (see Table 2).
ON
AUXON
12S+
12V and 3.3V Outputs Enable. A logic-high at ON turns on the 12V and 3.3V outputs (see Table 2).
3.3V Auxiliary Output Enable. A logic-high at AUXON turns on the auxiliary output (3.3VAUXO) (see Table 2).
12V Positive Current-Sense Input. Connect the positive terminal of the current-sense resistor to 12S+
using the Kelvin-sensing technique to assure accurate current sensing.
12S-
12G
12V Negative Current-Sense Input. Connect 12S- to the negative side of the current-sense resistor using
the Kelvin-sensing technique to assure accurate current sensing.
12V Gate-Drive Output. Connect 12G to the gate of the 12V MOSFET. At power-up, V_12G
is raised to the internal charge-pump voltage level by a constant current.
3.3S+
3.3V Positive Current-Sense Input. Connect the positive side of the current-sense resistor to 3.3S+ using
the Kelvin-sensing technique to assure accurate current sensing. This input is also used for the 3.3V
supply’s UVLO function.
3.3S-
3.3V Negative Current-Sense Input. Connect to the negative side of the sense resistor using the Kelvin-
sensing technique to assure accurate current sensing.
3.3G
FAULT
3.3V Gate-Drive Output. Connect 3.3G to the gate of the 3.3V MOSFET. At power-up, V_3.3G
is charged to 5.5V above the 3.3V supply by a constant current derived from V_12VIN.
Open-Drain Fault Output Signal. FAULT latches active low whenever the 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, FAULT must be reset by toggling the ON input. If the fault is in
the auxiliary output, FAULT must be reset by toggling both ON and AUXON. For the auto-restart version,
FAULT is reset when the part initiates the next power-on cycle.
PWRGD
Open-Drain Power-Good Output. PWRGD goes low t_{POR_HL} after all outputs reach their final value and
the power MOSFETs are fully enhanced.
3.3VAUXO 3.3V Auxiliary Power-Supply Output
3.3VAUXIN
3.3V Auxiliary Supply Input. 3.3VAUXIN is the input to a charge pump that drives the internal MOSFET
connecting 3.3VAUXIN to 3.3VAUXO. V_3.3VAUXIN is also used to power the internal control logic and
analog references of the MAX5954.
N.C.
T1
No Connection. Not internally connected.
Test Input. Connect T1 to GND.
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