DA14706 hibernation

Question

Hi! 
 I tried to run pmu_wakeup_demo from github.com/.../BLE_SDK10_DA1470x_examples on DA14706 DevKit. 
 When I enable hibernation mode, power consumption decreases to 200 - 300 nA, and seems it is really hibernation. (It can't wake up by reset or power switching, only by connecting Vbus). 
 Vbat voltage is 3.3 V. 
 The main problem is Vsys voltage in hibernation is about 2.9 Volts and I still can power external devices from it (after connection external device to Vsys, consumption increases to 10 mA). 
 As I understand based on documentation, device should open sysbat switch and as a result power off all peripheral, connected to Vsys. 
 
 I tried to set FORCE_VBAT_VSYS_SW register manually for open switch this switch, but it had no result. 
 My device in &ldquo;Shipping mode&rdquo; should disable all external peripheral, I hope I do something wrong. 
 What can be problem? 
 Do I need to prepare DA14706 to hibernation mode? May be you have some guidelines for it? 
 Does it really possible to disable Vsys at all, or I need to use external power control scheme?

JH_Renesas · Accepted Answer

Hi Kars, 
 Sorry for the delay, I got updates form team, here is the details: 
 the VBAT Switch between the VBAT and VSYS rail actually is an ideal diode: realized by a FET circuit. It requires biasing. When VBAT is supplying VSYS, the diode is conducting (switch closed) and its forward voltage drop is ~25 mV. It acts as a diode in reverse (switch open) for cases VSYS > VBAT when e.g. VSYS is supplied by VBUS via the LDO_VSYS. But, when the VBAT Switch is not active (in hibernation mode the diode circuit is not biased), a parasitic diode between VBAT and VSYS will cause the VSYS rail to be at VBAT voltage minus a diode-voltage drop: VBAT minus ~0.5 V. So even if the VSYS Generation = Off in Hibernation Mode, the VSYS voltage will be VBAT minus ~0.5 V because of the parasitic diode in the VBAT-VSYS Switch when the switch-circuit is not biased (e.g. when in Hibernation mode). This cannot be avoided unfortunately. As a 2nd consequence, VLED will be a diode voltage drop lower than VSYS because of the before-mentioned parasitic diode in the DCDC booster path. 
 => my data of DA14706 Pro-DK board. SW: SDK PXP_Reporter with Sleep-Mode set to Hibernation_Mode. The rail voltages were measured using 1 MOhm probes.

Vbat 
 Vsys 
 Vled 
 V30 
 V18p 
 V18 
 V14 
 V12

3.34 V 
 2.86 V 
 2.63 V 
 ~0 V 
 ~0 V 
 ~0 V 
 ~0 V 
 ~0 V

Vbat - Vsys = 0.48 V ; Vsys - Vled = 0.23 V. 
 Vled loaded with 25 KOhm resistor (to see better the voltage drop of the parasitic diodes).

Vbat 
 Vsys 
 Vled 
 V30 
 V18p 
 V18 
 V14 
 V12

3.34 V 
 2.74 V 
 2.44 V 
 ~0 V 
 ~0 V 
 ~0 V 
 ~0 V 
 ~0 V

Vbat - Vsys = 0.6 V ; Vsys - Vled = 0.3 V.

JH_Renesas · Answer

Hi Kars, 
 another customer used a load-switch in their application to cut off VSYS to external circuits - to prevent leakage at Vsys or Vled during hibernation mode. Load-switch example: GLF71301 - GLF Integrated Power (glfipower.com) 
 BR, 
 JH_Renesas

JH_Renesas · Answer

Hi Kars, 
 About the hibernation mode please refer to this tutorial: 3. BSP &mdash; DA1470x Software Platform Reference (renesas.com) 
 
 The VSYS will close when entering the hibernation mode. 
 
 In this header file you can get the APIs: 
 
 BR, 
 Jason

DA14706 hibernation

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