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

USB_MICRO_B

J5

1

2

3

4

5

R6

100K

R8

200K

1

3

TP1

SILK = VOUT

C5

2.2uF

C6

2.2uF

U2

AP2127K-ADJTRG1

VIN

1

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

11 / 31