M1AFS600-PQ208 Datasheet, PDF (109/334 Pages) Microsemi Corporation – Fusion Family of Mixed Signal FPGAs

Fusion Family of Mixed Signal FPGAs
Gate Driver
The Fusion Analog Quad includes a Gate Driver connected to the Quad's AG pin (Figure 2-74).
Designed to work with external p- or n-channel MOSFETs, the Gate driver is a configurable current sink
or source and requires an external pull-up or pull-down resistor. The AG supports 4 selectable gate drive
levels: 1 µA, 3 µA, 10 µA, and 30 µA (Figure 2-75 on page 2-94). The AG also supports a High Current
Drive mode in which it can sink 20 mA; in this mode the switching rate is approximately 1.3 MHz with
100 ns turn-on time and 600 ns turn-off time. Modeled on an open-drain-style output, it does not output a
voltage level without an appropriate pull-up or pull-down resistor. If 1 V is forced on the drain, the current
sinking/sourcing will exceed the ability of the transistor, and the device could be damaged.
The AG pad is turned on via the corresponding GDONx pin in the Analog Block macro, where x is the
number of the corresponding Analog Quad for the AG pad to be enabled (GDON0 to GDON9).
Power
Line Side
Load Side
Off-Chip
Pads
On-Chip
AV
Voltage
Monitor Block
Prescaler
R_pullup
AC
Current
Monitor Block
AG
Gate
Driver
AT
Temperature
Monitor Block
Analog Quad
Prescaler
Prescaler
Digital
Input
Digital
Input
Current
Monitor / Instr
Amplifier
Power
MOSFET
Gate Driver
Digital
Input
Temperature
Monitor
To FPGA
(DAVOUTx)
To Analog MUX
To FPGA
(DACOUTx)
From FPGA
(GDONx)
To Analog MUX
To FPGA
(DATOUTx)
To Analog MUX
Figure 2-74 • Gate Driver
The gate-to-source voltage (V_gs) of the external MOSFET is limited to the programmable drive current
times the external pull-up or pull-down resistor value (EQ 5).
V_gs  I_g × (R_pullup or R_pulldown)
EQ 5
The rate at which the gate voltage of the external MOSFET slews is determined by the current, I_g,
sourced or sunk by the AG pin and the gate-to-source capacitance, C_GS, of the external MOSFET. As an
approximation, the slew rate is given by EQ 6.
dv/dt = I_g / C_GS
EQ 6
Revision 4
2- 93