Voltage Reference Buffer (Vrefbuf); Introduction; Vrefbuf Functional Description; Table 120. Vref Buffer Modes - ST STM32WL5 Series Reference Manual

RM0453
20

Voltage reference buffer (VREFBUF)

20.1

Introduction

The devices embed a voltage reference buffer which can be used as voltage reference for
ADC, DAC and also as voltage reference for external components through the VREF+
pin.When the VREF+ pin is double-bonded with VDDA pin in a package, the voltage
reference buffer is not available and must be kept disabled (refer to datasheet for packages
pinout description).
20.2

VREFBUF functional description

The internal voltage reference buffer supports two voltages
VRS bits in the VREFBUF_CSR register:
•
VRS = 0: V
•
VRS = 1: V
The internal voltage reference can be configured in four different modes depending on
ENVR and HIZ bits configuration. These modes are provided in the table below:
ENVR
0
0
1
1
After enabling the VREFBUF by setting ENVR bit and clearing HIZ bit in the VREFBUF_CSR register,
the user must wait until VRR bit is set, meaning that the voltage reference output has reached its
expected value.
a. The minimum V
around 2.048 V.
REF_OUT1
around 2.5 V.
REF_OUT2

Table 120. VREF buffer modes

HIZ
VREFBUF buffer off mode:
0
– V pin pulled-down to V
REF+
External voltage reference mode (default value):
1 – VREFBUF buffer off
– V pin input mode
REF+
Internal voltage reference mode:
0 – VREFBUF buffer on
– V pin connected to VREFBUF buffer output
REF+
Hold mode:
– VREFBUF buffer off
1
– V pin floating. The voltage is held with the external capacitor
REF+
– VRR detection disabled and VRR bit keeps last state
voltage depends on VRS setting, refer to the product datasheet.
DDA
RM0453 Rev 1
Voltage reference buffer (VREFBUF)
(a)
, which are configured with
VREF buffer configuration
SSA
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