Lattice Semiconductor L-ASC10 User Manual - page 18
18
ASC Breakout Board
The 5 V Hot Swap circuit is designed to support two separate implementations. The Standard MOSFET implemen-
tation uses a standard power MOSFET (Q6) and a 5 m
Ω sense resistor (R60). The MOSFET with Sense output
implementation uses a power MOSFET with current sense output (Q5) and a 3.30
Ω sense resistor. The Standard
MOSFET implementation is a Load-based Hot Swap implementation with the MOSFET connected between the
current sensing resistor and the load capacitor. The MOSFET with Sense output implementation is a Supply-based
Hot Swap implementation with the MOSFET connected between the supply and the current sensing resistor. The
full 5 V Hot Swap circuit is shown in Figure 14 below.
MOSFET with Sense Output
Q5
3
6
N-Channel MOSFET supply-side Hot Swap switch supplies
power to +5V_HS and load capacitor C13. Sense output pro-
vides proportional current to drain current.
Gate Drive Resistor
R54
3
6
2.2 k
Ω
resistor, located close to MOSFET Q5, limits parasitic
oscillations at the gate of Q5. Works with C23 to slow switching
at Q5, limiting current ripple during hysteretic switching.
Current sense resistor
R57
3
6
3.30
Ω
sense resistor for supply-side current monitoring with
IMON1 input of ASC, connected to Sense output of MOSFET
(Q5)
IMON1 Isolation Resistor
R55
3
, R56
3
6
Zero
Ω
resistors – support population option for MOSFET with
Sense output versus standard MOSFET
Gate-Source Capacitor
C23
3
6
100 nF capacitor, works with R54 to slow switching at Q5, lim-
iting current ripple during hysteretic switching.
Load Capacitors
C13
1
6
680 µF 10 V Bulk capacitance emulates a Hot Swap load.
Discharge Resistors
R62
1
6
4.7 k
Ω
Resistor discharges load capacitor between Hot
Swaps.
LED Bias Resistor
R63
6
3.3 k
Ω
resistor limits the LED current for D10.
Red Indicator LED
D10
6
LED to indicate Hot Swap has completed successfully.
Phoenix 2-Terminal Connector
J6
6
+5V_HS terminal block connector
Current Sense Amplifier
U2
1
6
ZXCT1009 current sense amplifier – provides output current
proportional to voltage across Vsense+ and Vsense-. Used for
demonstration purpose only, not required in application.
Current Sense Output Resistor
R94
1
6
20 k
Ω
resistor, sets output voltage at I_5V_HS test point to 1 V
/ 1A drain current of MOSFET.
NPN Fast Shutoff Transistor
Q7
6
NPN transistor, provides fast pull-down of Q5/Q6 gate voltage,
enables fast shutdown from FPGA via ASC Interface connec-
tor during Hot Swap faults
Shutoff Transistor Pull-up Resistor R64
6
1 k
Ω
pull-up resistor – biases Q7 ON by default (shutting off
Q5/Q6).
Signals
+5V_SW
2, 6
5 V input voltage, from Power Supply circuit and J1
5V_HS_DRIVE
2, 6
HVOUT2 signal from ASC
ASC_5V_OC_SHUTDOWN
2, 6
FPGA PIO signal, from ASC Interface Connector
5V_HS_CURRENT_P
2, 6
Connected to IMON1A_P, positive current monitor terminal
5V_HS_CURRENT_N
2, 6
Connected to IMON1A_N, negative current monitor terminal
+5V_HS
2, 4, 6
5 V Hot Swap output voltage, provided to J6 terminal block,
ASC Interface Connector, and DCDC1 and 2 input voltage
Additional Test Points
I_5V_HS
Current Sense Amplifier Output Voltage – 1 V per 1A
1.Not required for customer designs; this is only needed to support ASC device evaluation.
2.Only populate for 5 V Standard MOSFET Hot Swap. Populate only from either Note 2 or Note 3, never both.
3.Only populate for 5 V MOSFET with Sense output Hot Swap. Populate only from either Note 3 or Note 3, never both.
Component / Signals
Ref. Des.
Schematic
Sheet
Description