Encryption Key Backup Circuit - Xilinx ZC702 User Manual

Encryption Key Backup Circuit

The XC7Z020 SoC U1 implements bitstream encryption key technology. The ZC702 board
provides the encryption key backup battery circuit shown in
X-Ref Target - Figure 1-5
The Seiko TS518FE rechargeable 1.5V lithium button-type battery B1 is soldered to the
board with the positive output connected to the XC7Z020 SoC U1 VCCBATT pin G9. The
battery supply current IBATT specification is 150 nA maximum when board power is off. B1
is charged from the VCCAUX 1.8V rail through a series diode with a typical forward voltage
drop of 0.38V and 4.7 K
ZC702 Board User Guide
UG850 (v1.7) March 27, 2019
D8
40V
200 mW
To SoC
U1 Pin G9
FPGA_VBATT
(VCCBATT)
B1
Figure 1-5: Encryption Key Backup Circuit
current limit resistor. The nominal charging voltage is 1.42V.
Ω
www.xilinx.com
Figure 1-5.
NC
1
VCCAUX
3
BAS40-04
2
R2
4.70K 1%
1/16Ω
1
+
Lithium Battery
Seiko
TS518SE_FL35E
1.5V
2
GND
UG850_c1_05_0632719
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