20
ASC Breakout Board
Figure 15. 5 V Hot Swap - Load-Based, Standard MOSFET
The signals 5V_HS_CURRENT_P and 5V_HS_CURRENT_N are connected to the IMON1P and IMON1N signals
of the ASC. The sensing resistor R60 is connected through the zero
Ω
isolation resistors (R58, 59) to the ASC
using Kelvin connections and differential layout techniques to maximize the current sensing accuracy at the IMON1
inputs.
The +5V_HS signal is used by the Hot Swap function to monitor the load capacitor C13 voltage using VMON6 of
the ASC. The Hot Swap function monitors the load capacitor C13 voltage for the following reasons:
• to see that C13 is charging up and there is not a short or open in the circuit
• to see that C13 has reached a voltage where a higher current limit can be used
• to know when C13 is close to the 5 V supply voltage – Hot Swap is complete.
When Hot Swap is disabled R62 provides a discharge path for C13 to prepare the circuit for subsequent Hot
Swaps. LED D10 and bias resistor R63 give a visual indication that the Hot Swap process is complete.
Supply-Based Hot Swap (MOSFET with Sense Output)
The circuit in Figure 16 illustrates the Supply-based Hot Swap using a MOSFET with Sense output. (Components
from the Standard MOSFET Hot Swap are shown to illustrate the shared connections between the two circuits. Q6,
R58, R59, R60, R61, C22 should not be populated when the MOSFET with Sense output is used.) The MOSFET
with Sense output variation has Q5 connected to the supply side of R57. The SENSE output of Q5 provides a cur-
rent proportional to the current flowing through the MOSFET drain (the BUK7C06 shown in the schematic has a
typical drain current to sense current ratio of 615). The N type MOSFET Q5 is controlled by the HVOUT2 output
from the ASC. The gate resistor (R54) and gate-source capacitor (C23) are used to maintain a soft turn on of Q5.
The increased gate capacitance smooths out the current during the hysteretic control stage (see the References
section for more details on the Hot Swap behavior).
Shared
Connection with
MOSFET with Sense
Hot Swap
VMON6
+5
V
_HS
R5
8
0
R60
0.005
2
W
, 1%
R59
0
C22
100nF
R62
4.7k
R61
2.2k
D10
Red
SM_LED_0603
TP12
5
V
_HS
1
Q6
IRF7
8
32
J6
2 Position Terminal Block
A
B
R63
3.3k
C13
6
8
0
u
F
10
V
From 5V_SW
Supply Voltage
To ASC IMON 1P
Current Monitor
To ASC IMON 1N
Current Monitor
To Current Sense
Amplifier
From ASC
HVOUT2
