nPM1100 ship mode

[oqthm011]

Hi, I have a question with regard to the nPM1100 PMIC and entering ship mode (not exiting it).

If I am interpreting the datasheet correctly, the SHPHLD pin must be held HIGH prior to activating ship mode via SHPACT (correct me if I am wrong). The reference schematic in section 7.1 of the datasheet shows SHPHLD connected to VBAT via a 100k resistor and a switch connected to GND to pull it LOW when pressed.

In my scenario (no MCU involved) I want to be able to enter ship mode at the press of a button that sets SHPACT to HIGH (by connecting VSYS?), however, I don't need the switch with SHPHLD as I can exit ship mode bby connecting VBUS (the USB cable).

My questions are,

1. If I don't need the switch on SHPHLD, do I just connect SHPHLD directly to VBAT?

2. Do I still need the 100k resistor? Is there a significance to this value? The nPM1100 EK board uses two 10k resistors in series instead.

3. Under normal operation, isn't holding SHPHLD constantly HIGH, connected to VBAT, wasting battery life on the off-chance one needs to press the switch on SHPACT to enter ship mode?

4. If (3) is a yes, is there possibly another way to achieve entering ship mode by setting SHPHLD HIGH right before setting SHPACT HIGH?

Just to re-iterate, in my implementation no MCU is involved.

Thank you for your answers in advance

[Kazi Afroza Sultana]

Hello,

1. '' If I don't need the switch on SHPHLD, do I just connect SHPHLD directly to VBAT?''

Yes you can just connect SHPHLD directly to VBAT.

According to datasheet, ''there are two ways to exit Ship mode. Either connect the USB (VBUS) or set SHPHLD low for a minimum period of t_shipToActive. The battery supply (VBAT) is used to hold SHPHLD high through a weak pull-up resistor when Ship mode is enabled. A circuit to pull down SHPHLD is optional (see the Button switch shown in the following figure). If no pull-down circuit is present, Ship mode is exited when VBUS is connected.

Product overview • nPM1100 Product Specification • Technical Documentation

SO, if you don't need to switch. you can just connect this pin to VBAT to keep it high.

2. Do I still need the 100k resistor? Is there a significance to this value? The nPM1100 EK board uses two 10k resistors in series instead.

100kohm is current limiting pull up resistor. If you don't need the wake up button you can omit this part. 

The 100k mentioned is the datasheet is chosen for minimizing current in a battery product. the EK hardware design focuses on having less noise over uA level current. 

3.  Under normal operation, isn't holding SHPHLD constantly HIGH, connected to VBAT, wasting battery life on the off-chance one needs to press the switch on SHPACT to enter ship mode?

I don't think so as BUTTON is open and in such condition SHPHLD is a high impedance input. 

4.  Since the number 3 answer is no. You have very straight forward approach to enter ship according to datasheet, (Product overview • nPM1100 Product Specification • Technical Documentation)

"To enter Ship mode, SHPACT must be set high for a minimum period of tactiveToShip = 200 ms when VBUS is disconnected and SHPHLD held high.''

So, to enter Ship mode, you have to follow the following steps:

1. Connect a button between SHPACT and VBAT.

2. Button should be pressed at least for 200ms. 

3. When button is not pressed, internal pull down (500kohm) holds SHPACT low. 

Thanks.

BR

Kazi

[oqthm011]

Thank you for your answer.

Regarding your reply in (3), what I actually meant was that since I'll be permanently wiring SHPHLD to VBAT (without a button) won't that be wasting battery by keeping SHPHLD permanently HIGH (again without a button)?

I don't have space on my board for two switches (one for SHPACT and one for SHPHLD).

Thank you

[Bendik Heiskel]

Hi,

If you're not going to be using the SHPHLD pin at all you can just connect it directly to GND. like in configurations 1 and 2 of the reference schematic:

 

Best regards,

Bendik