diff --git a/Marlin/Configuration.h b/Marlin/Configuration.h
index 0dd0c3aa9cb8..550ea354676f 100644
--- a/Marlin/Configuration.h
+++ b/Marlin/Configuration.h
@@ -379,8 +379,8 @@
  *    13 : 100k Hisens 3950  1% up to 300°C for hotend "Simple ONE " & "Hotend "All In ONE"
  *    15 : 100k thermistor calibration for JGAurora A5 hotend
  *    18 : ATC Semitec 204GT-2 (4.7k pullup) Dagoma.Fr - MKS_Base_DKU001327
- *    20 : Pt100 with circuit in the Ultimainboard V2.x
- *    21 : Pt100 with circuit on 32 bit mcu
+ *    20 : Pt100 with circuit in the Ultimainboard V2.x with 5v excitation (AVR)
+ *    21 : Pt100 with circuit in the Ultimainboard V2.x with 3.3v excitation (STM32 \ LPC176x....)
  *   201 : Pt100 with circuit in Overlord, similar to Ultimainboard V2.x
  *    60 : 100k Maker's Tool Works Kapton Bed Thermistor beta=3950
  *    61 : 100k Formbot / Vivedino 3950 350C thermistor 4.7k pullup
diff --git a/Marlin/src/lcd/thermistornames.h b/Marlin/src/lcd/thermistornames.h
index 88ea5d253994..3ac230f7870a 100644
--- a/Marlin/src/lcd/thermistornames.h
+++ b/Marlin/src/lcd/thermistornames.h
@@ -87,7 +87,7 @@
 #elif THERMISTOR_ID == 20
   #define THERMISTOR_NAME "Pt100 UltiMB"
 #elif THERMISTOR_ID == 21
-  #define THERMISTOR_NAME "Pt100 32 bit"
+  #define THERMISTOR_NAME "Pt100 UltiMB"
 #elif THERMISTOR_ID == 201
   #define THERMISTOR_NAME "Pt100 OverLord"
 #elif THERMISTOR_ID == 60
diff --git a/Marlin/src/module/thermistor/thermistor_21.h b/Marlin/src/module/thermistor/thermistor_21.h
index 44d1dc42727d..c215fbfbeaea 100644
--- a/Marlin/src/module/thermistor/thermistor_21.h
+++ b/Marlin/src/module/thermistor/thermistor_21.h
@@ -23,7 +23,7 @@
 
 #define REVERSE_TEMP_SENSOR_RANGE
 
-// Pt100 with INA826 amp on 32 bit mcu based on "Pt100 with INA826 amp on Ultimaker v2.0 electronics"
+// Pt100 with INA826 amp with 3.3v excitation based on "Pt100 with INA826 amp on Ultimaker v2.0 electronics"
 const short temptable_21[][2] PROGMEM = {
   { OV(  0),    0 },
   { OV(344),    1 },
diff --git a/Marlin/src/module/thermistor/thermistors.h b/Marlin/src/module/thermistor/thermistors.h
index 4d3cc72b9ac8..c014d0571aa2 100644
--- a/Marlin/src/module/thermistor/thermistors.h
+++ b/Marlin/src/module/thermistor/thermistors.h
@@ -105,7 +105,7 @@
 #if ANY_THERMISTOR_IS(20) // Pt100 with INA826 amp on Ultimaker v2.0 electronics
   #include "thermistor_20.h"
 #endif
-#if ANY_THERMISTOR_IS(21) // Pt100 with INA826 amp on 32 bit mcu based "Pt100 with INA826 amp on Ultimaker v2.0 electronics"
+#if ANY_THERMISTOR_IS(21) // Pt100 with INA826 amp with 3.3v excitation based on "Pt100 with INA826 amp on Ultimaker v2.0 electronics"
   #include "thermistor_21.h"
 #endif
 #if ANY_THERMISTOR_IS(51) // beta25 = 4092 K, R25 = 100 kOhm, Pull-up = 1 kOhm, "EPCOS"