IO20PDB0V0 datasheet(118/197 Pages) MICROSEMI

118 / 197 page

Pin Descriptions

5- 4

R ev isio n 1 2

VJTAG

Supply

Digital supply to the JTAG controller

SmartFusion cSoCs have a separate bank for the dedicated JTAG pins. The JTAG pins

can be run at any voltage from 1.5 V to 3.3 V (nominal). Isolating the JTAG power

supply in a separate I/O bank gives greater flexibility in supply selection and simplifies

power supply and PCB design. If the JTAG interface is neither used nor planned to be

used, the VJTAG pin together with the TRSTB pin could be tied to GND. Note that VCC

is required to be powered for JTAG operation; VJTAG alone is insufficient. If a

SmartFusion cSoC is in a JTAG chain of interconnected boards and it is desired to

power down the board containing the device, this can be done provided both VJTAG

and VCC to the device remain powered; otherwise, JTAG signals will not be able to

transition the device, even in bypass mode. See "JTAG Pins" section on page 5-10.

VPP

Supply

Digital programming circuitry supply

SmartFusion cSoCs support single-voltage in-system programming (ISP) of the

configuration flash, embedded FlashROM (eFROM), and embedded nonvolatile

memory (eNVM).

For programming, VPP should be in the 3.3 V ± 5% range. During normal device

operation, VPP can be left floating or can be tied to any voltage between 0 V and 3.6 V.

When the VPP pin is tied to ground, it shuts off the charge pump circuitry, resulting in no

sources of oscillation from the charge pump circuitry. For proper programming, 0.01μF,

and 0.1μF to 1μF capacitors, (both rated at 16 V) are to be connected in parallel across

VPP and GND, and positioned as close to the FPGA pins as possible.

Name

Type

Description

Notes:

1. The following 3.3 V supplies should be connected together while following proper noise filtering practices: VCC33A,

VCC33ADCx, VCC33AP, VCC33SDDx, VCCMAINXTAL, and VCCLPXTAL.

2. The following 1.5 V supplies should be connected together while following proper noise filtering practices: VCC,

VCC15A, and VCC15ADCx.

3. For more details on VCCPLLx capacitor recommendations, refer to the application note AC359, SmartFusion cSoC

Board Design Guidelines, the "PLL Power Supply Decoupling Scheme" section.

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