23
ASC Breakout Board
12 V Hot Swap (Not Populated)
The ASC Breakout Board provides a set of footprints and connections for implementing a 12 V Hot Swap circuit
using the ASC’s built in hardware. Table 9 lists the key elements associated with 12 V Hot Swap operation on the
ASC Breakout Board.
Table 9. 12 V Hot Swap Components and Signals
Component / Signals
Ref. Des.
Schematic
Sheet
Description
Components Not Populated on Breakout Board
Voltage Divider Resistor
R65, R66
7
3 k
Ω
(R65) and 1.02 k
Ω
(R66) to 12V_SW rail down to
below 5.9 V limit for VMON input
Zener Diode
D11
7
Zener Diode for VMON input protection. Limits VMON9 input
during transients and overvoltage.
MOSFET Switch
Q9
2
, Q10
7
N-Channel MOSFET Supply-side Hot Swap switches supply
power to +12V_HS and load capacitor C15.
Gate Drive Resistor
R71
2
, R72
7
2.2 k
Ω
resistors, located close to MOSFETs Q9 & Q10, limits
parasitic oscillations at the gates of Q9 & Q10. Works with C2,
C21 to slow switching at Q9 & Q10, limiting current ripple dur-
ing hysteretic switching.
Gate-Source Capacitor
C20
2
, C21
2
7
100nF capacitors, works with R71 & R72 to slow switching at
Q9 & Q10, limiting inrush current during Hot Swap start and
current ripple during hysteretic switching.
Current Sense Resistor
R73
7
10 m
Ω
3 W resistor for load side current monitoring with
HIMON input of ASC
HIMON Snubbing Resistor
R74
2
, R75
2
7
Snubber resistors (paired with C16, C17) protect HIMON input
from momentary overvoltage, including inductive flyback volt-
ages when Q9 and Q10 are turned off. Population option to
support standard MOSFET Q9 versus MOSFET with Sense
output Q11.
MOSFET with Sense Output
Q11
3
7
N-Channel MOSFET supply-side Hot Swap switch supplies
power to +12V_HS and load capacitor C15 with Q10. Sense
output provides proportional current to drain current.
Gate Drive Resistor
R67
3
7
2.2 k
Ω
resistor, located close to MOSFET Q11, limits parasitic
oscillations at the gate of Q11. Works with C26 to slow switch-
ing at Q11, limiting current ripple during hysteretic switching.
Current sense resistor
R68
3
7
6.20
Ω
resistor for supply-side current monitoring with HIMON
input of ASC using MOSFET with Sense output
HIMON Snubbing Resistor
R69
3
, R70
3
7
Snubber resistors (paired with C16, C17) protect HIMON input
from momentary overvoltage, including inductive flyback volt-
ages when Q10 and Q11 are turned off. Population option to
support MOSFET with Sense output Q11 versus standard
MOSFET Q9.
Gate-Source Capacitor
C26
3
7
100 nF capacitor, works with R67 to slow switching at Q11,
limiting inrush current during Hot Swap start and current ripple
during hysteretic switching.
HIMON Snubbing Capacitor
C16, C17
7
Snubber capacitors (paired with snubbing resistors) protect
HIMON input from momentary overvoltage, including inductive
flyback voltages when MOSFETs are turned off.
Load Capacitors
C15
1
7
1000 µF 25 V Bulk capacitance emulates a Hot Swap load.
Discharge Resistors
R76
1
7
10 k
Ω
Resistor discharges load capacitor between Hot Swaps.
LED Bias Resistor
R77
7
10 k
Ω
resistor limits the current through LED D12
Red Indicator LED
D12
7
LED to indicate 12 V Hot Swap is complete
Phoenix 2-Terminal Connector
J8
7
+12V_HS terminal block connector