isppac-powr1208p1 Lattice Semiconductor Corp., isppac-powr1208p1 Datasheet - Page 21

• Manufacturer Part Number: isppac-powr1208p1
• Description: In-system Programmable Power Supply Sequencing Controller And Precision Monitor
• Manufacturer: Lattice Semiconductor Corp.

Lattice Semiconductor
Figure 3-10. Gate and Source Voltage Responses for a 3.3V Supply
MOSFET gate capacitance ranges from hundreds to thousands of picoFarads. Refer to the MOSFET manufac-
turer’s data sheet for values of Cgs (Capacitance gate-to-source). If slower ramps are required, an additional exter-
nal low leakage capacitor (e.g. a polycarbonate or other poly type capacitor) can be added from the gate to ground.
As a good design practice, it is recommended that a series resistor of 10-100Ω be placed in the gate drive signal
near the FET gate pin to reduce the possibility that the FET may self-oscillate.
Charge Pump
Four internal charge pumps are provided to fully support external N-channel FET devices. No external components
are required for the charge pumps. The output voltage is programmable from 8 to 12V in 0.5V steps. The user must
select a high voltage limit no greater than 7.5V above V
trolled with an on-chip feedback loop, and is independent of the actual supply voltage.
Programmable Output Voltage Levels for HVOUT1- HVOUT4
There are eight selectable steps for the output voltage of the FET drivers when in FET driver mode. The output pins
HVOUT1-4 are current source outputs, each with a programmable current. The current is programmable in 32 dif-
ferent steps ranging from 0.5µA to 50µA. The voltage that the pin is capable of driving to is listed in Table 3-6. For
each supply range, the charge-pump range will be set by the software.
Table 3-6. HVOUT Gate Driver Voltage Range
V
DD
8.5
9.5
10
= 3.3V
8
9
3-21
DD
(the software assists this process). This voltage is con-
V
DD
10.5
8.5
9.5
10
11
12
8
9
= 5V
ispPAC-POWR1208P1 Data Sheet