diff --git a/Marlin/Configuration.h b/Marlin/Configuration.h
index 7f242dce7..550ea3546 100644
--- a/Marlin/Configuration.h
+++ b/Marlin/Configuration.h
@@ -379,7 +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
+ *    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 17772d788..9cfb80fba 100644
--- a/Marlin/src/lcd/thermistornames.h
+++ b/Marlin/src/lcd/thermistornames.h
@@ -85,7 +85,9 @@
 #elif THERMISTOR_ID == 18
   #define THERMISTOR_NAME "ATC Semitec 204GT-2"
 #elif THERMISTOR_ID == 20
-  #define THERMISTOR_NAME "Pt100 UltiMB"
+  #define THERMISTOR_NAME "Pt100 UltiMB 5v"
+#elif THERMISTOR_ID == 21
+  #define THERMISTOR_NAME "Pt100 UltiMB 3.3v"
 #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
new file mode 100644
index 000000000..e65f90b75
--- /dev/null
+++ b/Marlin/src/module/thermistor/thermistor_21.h
@@ -0,0 +1,77 @@
+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (c) 2019 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (c) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+#pragma once
+
+#define REVERSE_TEMP_SENSOR_RANGE
+
+#undef OV_SCALE
+#define OV_SCALE(N) (float((N) * 5) / 3.3f)
+
+// 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(227),    1 },
+  { OV(236),   10 },
+  { OV(245),   20 },
+  { OV(253),   30 },
+  { OV(262),   40 },
+  { OV(270),   50 },
+  { OV(279),   60 },
+  { OV(287),   70 },
+  { OV(295),   80 },
+  { OV(304),   90 },
+  { OV(312),  100 },
+  { OV(320),  110 },
+  { OV(329),  120 },
+  { OV(337),  130 },
+  { OV(345),  140 },
+  { OV(353),  150 },
+  { OV(361),  160 },
+  { OV(369),  170 },
+  { OV(377),  180 },
+  { OV(385),  190 },
+  { OV(393),  200 },
+  { OV(401),  210 },
+  { OV(409),  220 },
+  { OV(417),  230 },
+  { OV(424),  240 },
+  { OV(432),  250 },
+  { OV(440),  260 },
+  { OV(447),  270 },
+  { OV(455),  280 },
+  { OV(463),  290 },
+  { OV(470),  300 },
+  { OV(478),  310 },
+  { OV(485),  320 },
+  { OV(493),  330 },
+  { OV(500),  340 },
+  { OV(507),  350 },
+  { OV(515),  360 },
+  { OV(522),  370 },
+  { OV(529),  380 },
+  { OV(537),  390 },
+  { OV(544),  400 },
+  { OV(614),  500 }
+};
+
+#undef OV_SCALE
+#define OV_SCALE(N) (N)
diff --git a/Marlin/src/module/thermistor/thermistors.h b/Marlin/src/module/thermistor/thermistors.h
index 875f742cc..58e1ef115 100644
--- a/Marlin/src/module/thermistor/thermistors.h
+++ b/Marlin/src/module/thermistor/thermistors.h
@@ -37,7 +37,8 @@
   #error "MAX_RAW_THERMISTOR_VALUE is too large for int16_t. Reduce OVERSAMPLENR or HAL_ADC_RESOLUTION."
 #endif
 
-#define OV(N) int16_t((N) * (OVERSAMPLENR) * (THERMISTOR_TABLE_SCALE))
+#define OV_SCALE(N) (N)
+#define OV(N) int16_t(OV_SCALE(N) * (OVERSAMPLENR) * (THERMISTOR_TABLE_SCALE))
 
 #define ANY_THERMISTOR_IS(n) (THERMISTOR_HEATER_0 == n || THERMISTOR_HEATER_1 == n || THERMISTOR_HEATER_2 == n || THERMISTOR_HEATER_3 == n || THERMISTOR_HEATER_4 == n || THERMISTOR_HEATER_5 == n || THERMISTOR_HEATER_6 == n || THERMISTOR_HEATER_7 == n || THERMISTORBED == n || THERMISTORCHAMBER == n || THERMISTORPROBE == n)
 
@@ -105,6 +106,9 @@
 #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 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"
   #include "thermistor_51.h"
 #endif