VCU118 Board User Guide 20
UG1224 (v1.5) March 15, 2023
Chapter3: Board Component Descriptions
Encryption Key Battery Backup Circuit
The XCVU9P device U1 implements bitstream encryption key technology. The VCU118
board provides the encryption key backup battery circuit shown in Figure 3-1. The Seiko
TS518FE rechargeable 1.5V lithium button-type battery B1 is soldered to the board with the
positive output connected to the XCVU9P device U1 VBATT pin AT11. The battery supply
current I
BATT
specification is 150 nA maximum when the board power is off. B1 is charged
from the SYS_1V8 1.8V rail through a series diode with a typical forward voltage drop of
0.38V and 4.7 K current limit resistor. The nominal charging voltage is 1.42V.
X-Ref Target - Figure 3-1
Figure3‐1: Encryption Key Backup Circuit
To VBATT pin
U1.AT11
X18008-100416
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