diff --git a/hal/targets/hal/TARGET_Maxim/TARGET_MAX32620/sleep.c b/hal/targets/hal/TARGET_Maxim/TARGET_MAX32620/sleep.c
index 0ab40fa518..311325d932 100644
--- a/hal/targets/hal/TARGET_Maxim/TARGET_MAX32620/sleep.c
+++ b/hal/targets/hal/TARGET_Maxim/TARGET_MAX32620/sleep.c
@@ -38,12 +38,23 @@
 #include "clkman_regs.h"
 #include "ioman_regs.h"
 #include "rtc_regs.h"
+#include "usb_regs.h"
 #include "wait_api.h"
 
 #define REVISION_A3 2
 #define REVISION_A4 3
 
+// USB state to be restored upon wakeup
+typedef struct {
+    uint32_t dev_cn;
+    uint32_t dev_inten;
+    uint32_t ep_base;
+    uint32_t ep[MXC_USB_NUM_EP];
+} usb_state_t;
+
 static mxc_uart_regs_t *stdio_uart = (mxc_uart_regs_t*)STDIO_UART;
+static int restore_usb;
+static usb_state_t usb_state;
 
 void sleep(void)
 {
@@ -54,28 +65,79 @@ void sleep(void)
     __WFI();
 }
 
+static void usb_sleep(void)
+{
+    int i;
+
+    if (MXC_USB->cn & MXC_F_USB_CN_USB_EN) {
+        // The USB module will not survive Deep Sleep.
+
+        // Save the USB state to restore it upon wakeup
+        usb_state.dev_cn = MXC_USB->dev_cn;
+        usb_state.dev_inten = MXC_USB->dev_inten;
+        usb_state.ep_base = MXC_USB->ep_base;
+        for (i = 0; i < MXC_USB_NUM_EP; i++) {
+            usb_state.ep[i] = MXC_USB->ep[i] & (MXC_F_USB_EP_DIR | MXC_F_USB_EP_BUF2 | MXC_F_USB_EP_INT_EN | MXC_F_USB_EP_NAK_EN);
+        }
+        restore_usb = 1;
+
+        // Shut down the USB module.
+        MXC_USB->dev_inten = 0;
+        MXC_USB->dev_cn = 0;
+        MXC_USB->cn = 0;
+        restore_usb = 1;   // USB should be restored upon wakeup
+    }
+    else {
+        restore_usb = 0;
+    }
+}
+
+// Restore the USB module state.
+static void usb_wakeup(void)
+{
+    int i;
+
+    if (restore_usb) {
+        MXC_USB->cn = MXC_F_USB_CN_USB_EN;
+        MXC_USB->dev_cn = MXC_F_USB_DEV_CN_URST;
+        MXC_USB->dev_cn = 0;
+        for (i = 0; i < MXC_USB_NUM_EP; i++) {
+            MXC_USB->ep[i] = usb_state.ep[i];
+        }
+        MXC_USB->ep_base = usb_state.ep_base;
+        MXC_USB->dev_cn = usb_state.dev_cn;
+        MXC_USB->dev_inten = usb_state.dev_inten;
+        restore_usb = 0;
+    }
+}
+
 // Low-power stop mode
 void deepsleep(void)
 {
-    /* Deep Sleep is not yet supported. */
-    sleep();
-
-#if 0
     unsigned int part_rev = MXC_PWRMAN->mask_id0 & MXC_F_PWRMAN_MASK_ID0_REVISION_ID;
 
-    // Deep sleep is not working properly on Revisions A3 and earlier
+    // Deep Sleep is not working properly on Revisions A3 and earlier
     if (part_rev <= REVISION_A3) {
         sleep();
         return;
     }
 
     // Wait for all STDIO characters to be sent. The UART clock will stop.
-    while ( (((stdio_uart->tx_fifo_ctrl & MXC_F_UART_TX_FIFO_CTRL_FIFO_ENTRY)
-                >> MXC_F_UART_TX_FIFO_CTRL_FIFO_ENTRY_POS) > 0) || 
-                (!(stdio_uart->intfl & MXC_F_UART_INTFL_TX_DONE)) );
+    while ((stdio_uart->tx_fifo_ctrl & MXC_F_UART_TX_FIFO_CTRL_FIFO_ENTRY) ||
+           !(stdio_uart->intfl & MXC_F_UART_INTFL_TX_DONE));
 
     __disable_irq();
 
+    // Do not enter Deep Sleep if connected to VBUS
+    if (MXC_USB->dev_intfl & MXC_F_USB_DEV_INTFL_VBUS_ST) {
+        __enable_irq();
+        sleep();
+        return;
+    }
+
+    // The USB module will not survive Deep Sleep. Shut it down.
+    usb_sleep();
+
     // Make sure RTC is not pending before sleeping, if its still synchronizing
     // we might not wake up.
     while (MXC_RTCTMR->ctrl & MXC_F_RTC_CTRL_PENDING);
@@ -104,17 +166,20 @@ void deepsleep(void)
         MXC_PWRSEQ->msk_flags |= MXC_F_PWRSEQ_MSK_FLAGS_PWR_TVDD12_RST_BAD;
         MXC_PWRSEQ->reg0 &= ~(MXC_F_PWRSEQ_REG0_PWR_SVMTVDD12EN_RUN);
         MXC_PWRSEQ->reg0 |= MXC_F_PWRSEQ_REG0_PWR_SVMTVDD12EN_RUN;
-        MXC_PWRSEQ->msk_flags &= ~(MXC_F_PWRSEQ_MSK_FLAGS_PWR_TVDD12_RST_BAD);
+        MXC_PWRSEQ->msk_flags &= ~MXC_F_PWRSEQ_MSK_FLAGS_PWR_TVDD12_RST_BAD;
     }
 
     // Enable Retention controller
     MXC_PWRSEQ->retn_ctrl0 |= MXC_F_PWRSEQ_RETN_CTRL0_RETN_CTRL_EN;
 
+    // Clear the firstboot bit, which is generated by a POR event and locks out LPx modes
+    MXC_PWRSEQ->reg0 &= ~MXC_F_PWRSEQ_REG0_PWR_FIRST_BOOT;
+
     // Freeze GPIO using MBUS so that it doesn't flail while digital core is asleep
     MXC_PWRSEQ->reg1 |= MXC_F_PWRSEQ_REG1_PWR_MBUS_GATE;
 
     // Dummy read to make sure SSB writes are complete
-    if (MXC_PWRSEQ->reg0 & MXC_F_PWRSEQ_REG0_PWR_SYS_REBOOT) {}
+    MXC_PWRSEQ->reg0;
 
     if (part_rev == REVISION_A4) {
         // Note: ARM deep-sleep requires a specific sequence to clear event latches,
@@ -134,7 +199,9 @@ void deepsleep(void)
     // We'll wakeup here ...
 
     // Unfreeze the GPIO by clearing MBUS_GATE
-    MXC_PWRSEQ->reg1 &= ~(MXC_F_PWRSEQ_REG1_PWR_MBUS_GATE);
+    MXC_PWRSEQ->reg1 &= ~MXC_F_PWRSEQ_REG1_PWR_MBUS_GATE;
+
+    usb_wakeup();
 
     // Clear power sequencer event flags (write-1-to-clear)
     // RTC and GPIO flags are cleared in their interrupts handlers
@@ -153,5 +220,4 @@ void deepsleep(void)
                          MXC_F_PWRSEQ_FLAGS_PWR_TVDD12_BAD);
 
     __enable_irq();
-#endif
 }
diff --git a/libraries/USBDevice/USBDevice/USBHAL_Maxim.cpp b/libraries/USBDevice/USBDevice/USBHAL_Maxim.cpp
index d8fc0756d8..f23322f005 100644
--- a/libraries/USBDevice/USBDevice/USBHAL_Maxim.cpp
+++ b/libraries/USBDevice/USBDevice/USBHAL_Maxim.cpp
@@ -99,7 +99,7 @@ USBHAL::USBHAL(void)
 
     // reset the device
     MXC_USB->cn = 0;
-    MXC_USB->cn = 1;
+    MXC_USB->cn = MXC_F_USB_CN_USB_EN;
     MXC_USB->dev_inten = 0;
     MXC_USB->dev_cn = 0;
     MXC_USB->dev_cn = MXC_F_USB_DEV_CN_URST;
@@ -129,6 +129,9 @@ USBHAL::USBHAL(void)
     // set the descriptor location
     MXC_USB->ep_base = (uint32_t)&ep_buffer_descriptor;
 
+    // enable VBUS interrupts
+    MXC_USB->dev_inten = MXC_F_USB_DEV_INTEN_NO_VBUS | MXC_F_USB_DEV_INTEN_VBUS;
+
     // attach IRQ handler and enable interrupts
     instance = this;
     NVIC_SetVector(USB_IRQn, (uint32_t)&_usbisr);