NXP Semiconductors PCF2131-ARD, Руководство пользователя, Страница: 11 / 31

NXP Semiconductors
UM11597
PCF2131-ARD evaluation board
dongle pullup resistors, and cause the ramp up time on the VDD to change. The
overall power path is illustrated below.
aaa-043567
Rp2
PCF2131
3.3 V
EXTERNAL INTERFACE
TOOL
PCX2131TF EVM
SCL
SDA
VSS
VDD
Rp1
3.3 V
SCL
SDA
R1
VDD_3V3
R2
R/C FILTER
C3
C4
R5
Figure 5. PCF2131-ARD daughterboard, pullup resistors detail
To prevent the dongle from back powering the EVM, the following should be
performed by the user (see Figure 6 ):
• The interface dongle should be plugged into the EVM after PCX2131TF or EVM is
powered up.
• If a user desires to keep the interface dongle plugged in regardless of the power
state of PCX2131TF, the following steps are recommended:
– Disable the interface dongle’s pullup resistors on the interface pins (SCL/SDA),
either through hardware or software control. Use onboard interface pullup
resistors R1 and R2.
– If the interface dongle’s pullup resistors can’t be disabled, remove the jumpers on
J15 1&2, and 3&4 on the EVM board.
3. BBS monitor:
BBS pin output can be monitored on J9.9
aaa-043568
VDD_5V_IN
VDD_3V3
VDD_3V3_IN
VB
US
D-
D+
ID
G
USB_MICRO_B
J5
1
2
3
4
S2
5
S
1
S
3
S4
S
5
S6
R6 100K
R8 200K
1 3
2
TP1
SILK = VOUT
C5
2.2uF
C6
2.2uF
U2
AP2127K-ADJTRG1
VIN
1
2
GND
SHUTDOWN
3
NC/ADJ
4
VOUT
5
TP2
SILK = GND
R7 18K
J14
HDR TH 1X3
1
2
3
Figure 6. PCF2131-ARD daughterboard, LDO regulator section
PCX2131TF evaluation board can be powered through two different power sources,
either from Arduino header’s 3.3V directly by selecting J14.1&2, or from an external
micro USB (J5, 5V input) through an adjustable LDO by selecting J14.2&3 ( Figure 6 ).
Note that the Arduino header only supplies fixed 3.3V, and might not be suitable for
evaluating a different power supply range. The on-board LDO can adjust the output
voltage from 1.2V to 5V.
Table 4 summarizes which source to use for different evaluation purposes.
UM11597 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2021. All rights reserved.
User manual Rev. 1.0 — 15 September 2021
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