diff --git a/connectivity/drivers/emac/TARGET_STM/TARGET_STM32H7/TARGET_PORTENTA_H7/stm32h7_eth_init.c b/connectivity/drivers/emac/TARGET_STM/TARGET_STM32H7/TARGET_PORTENTA_H7/stm32h7_eth_init.c
index 53de30a37f..3be5096b14 100644
--- a/connectivity/drivers/emac/TARGET_STM/TARGET_STM32H7/TARGET_PORTENTA_H7/stm32h7_eth_init.c
+++ b/connectivity/drivers/emac/TARGET_STM/TARGET_STM32H7/TARGET_PORTENTA_H7/stm32h7_eth_init.c
@@ -31,6 +31,7 @@
 #ifndef USE_USER_DEFINED_HAL_ETH_MSPINIT
 
 #include "stm32h7xx_hal.h"
+#include "portenta_power.h"
 
 #define ETH_TX_EN_Pin GPIO_PIN_11
 #define ETH_TX_EN_GPIO_Port GPIOG
@@ -59,6 +60,8 @@ void HAL_ETH_MspInit(ETH_HandleTypeDef *heth)
     GPIO_InitTypeDef GPIO_InitStruct;
     if(heth->Instance == ETH)
     {
+        enableEthPowerSupply();
+        
         #if !(defined(DUAL_CORE) && defined(CORE_CM4))
         /* Disable DCache for STM32H7 family */
         SCB_DisableDCache();
diff --git a/targets/TARGET_STM/TARGET_STM32H7/TARGET_STM32H747xI/TARGET_PORTENTA_H7/portenta_power.cpp b/targets/TARGET_STM/TARGET_STM32H7/TARGET_STM32H747xI/TARGET_PORTENTA_H7/portenta_power.cpp
new file mode 100644
index 0000000000..92f43b6ad4
--- /dev/null
+++ b/targets/TARGET_STM/TARGET_STM32H7/TARGET_STM32H747xI/TARGET_PORTENTA_H7/portenta_power.cpp
@@ -0,0 +1,54 @@
+/*
+  Copyright (c) 2019 Arduino.  All right reserved.
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  This library 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 Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with this library; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+/******************************************************************************
+   INCLUDE
+ ******************************************************************************/
+
+#include "mbed.h"
+#include "portenta_power.h"
+
+/******************************************************************************
+   PUBLIC MEMBER FUNCTIONS
+ ******************************************************************************/
+void enableEthPowerSupply(void)
+{
+  /* Ensure ETH power supply */
+  mbed::I2C i2c(PB_7, PB_6);
+  
+  char data[2];
+
+  // LDO3 to 1.2V
+  data[0]=0x52;
+  data[1]=0x9;
+  i2c.write(8 << 1, data, sizeof(data));
+  data[0]=0x53;
+  data[1]=0xF;
+  i2c.write(8 << 1, data, sizeof(data));
+  
+  // SW2 to 3.3V (SW2_VOLT)
+  data[0]=0x3B;
+  data[1]=0xF;
+  i2c.write(8 << 1, data, sizeof(data));
+
+  // SW1 to 3.0V (SW1_VOLT)
+  data[0]=0x35;
+  data[1]=0xF;
+  i2c.write(8 << 1, data, sizeof(data));
+  
+}
diff --git a/targets/TARGET_STM/TARGET_STM32H7/TARGET_STM32H747xI/TARGET_PORTENTA_H7/portenta_power.h b/targets/TARGET_STM/TARGET_STM32H7/TARGET_STM32H747xI/TARGET_PORTENTA_H7/portenta_power.h
new file mode 100644
index 0000000000..89b695f42f
--- /dev/null
+++ b/targets/TARGET_STM/TARGET_STM32H7/TARGET_STM32H747xI/TARGET_PORTENTA_H7/portenta_power.h
@@ -0,0 +1,33 @@
+/*
+  Copyright (c) 2019 Arduino.  All right reserved.
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  This library 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 Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with this library; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#ifndef PORTENTA_POWER
+#define PORTENTA_POWER
+
+
+#if defined(__cplusplus)
+extern "C" {
+#endif /* __cplusplus */
+
+extern void enableEthPowerSupply(void);
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif