Experiment of Ben NanoNote's Charge Cycle

I just edited this at Qi Hardware wiki. So you can also see this article here.

Purpose of Experiment 
    To understand that how does Ben NanoNote’s charge cycle work.

Test Product
    BEN NanoNote

Equipments
    Agilent 34401A Multimeter
    CHY 48R Multimeter

Methods of Connection
    Current connection:

Figure 1

Schematic

Figure 2

State Diagram of a Typical Charge Cycle

Figure 3

Study System Voltage Specification

Before this experiment, let’s see how Ben’s design and how to choose low voltage detector first. Because the Ben has jz4720 VDDIO voltage (2.97~3.63V) see page 24 of datasheet [1], the NANAD FLASH K9GAG08U0M has Vcc range (2.7~3.6V), also SDRAM P3V56S40ETP has VDD range (3.0~3.6V). So a low voltage detector circuit that can shut down the cpu jz4720 when monitors Battery’s voltage goes down -VDET (2.94~3.06V) detected by BL8506-30NRM, and the Battery has a over-discharge protect voltage 2.25V.

Figure 4

Through figure 4, we can easily know the best working power voltage for ben should be between upper limited 3.6V of SDRAM and lower limited 3.0V of SDRAM. That’s their intersection. Of course if there’s an sdram with widely working voltage like nand flash at lower 2.7V. That would be good to lengthen discharging time. But then the intersection becomes 2.97V caused by cpu. Since battery cell has overdischarge protect voltage 2.25V, strongly recommended that the software should be possessed of a detector of monitoring battery voltage under 3.0 voltages to make sure sdram can work normally. That’s the reason why ben has a low voltage detector BL8506-30NRM [3] which is based on 3.0±0.06 V detection precision ±2%.

Charge Status Indicator (CHRG), pin1 of SE9016
From its datasheet [2], this pin can output three status: strong pull down(~ 10mA), weak pull down (~20uA) and high impedance. So D3 LED can be as indicator shown if charging or not.

Experimental Data
From SE9016 datasheet [2], when BEN is on Power ON mode (Display On) , PW_ON_N is low; so RPROG = R15 = 10KΩ, from Data collection, IBAT = (VPROG / RPROG ) * 1100, then we can calculate VPROG inversely from measured IBAT.
Before measurement, make sure that the battery is above 3.06V, otherwise the low voltage detects will tell s/w to shut down cpu and will enter POWER OFF mode. This experiment will split into two modes to measure different charge current.

Case a: POWER ON mode, PW_ON_N is low, Display ON, Slow charging
Case b: POWR OFF mode, PW_ON_N is high, Display OFF, Fast charging
We firstly let BEN entered into POWER ON mode to keep the RPROG equaled to 10KΩ, not 2 KΩ. (if enters POWER OFF mode, the high PW_ON_N will let Q3 TM2302FN turned on then RPROG is R14//R15. see figure 2). From the measured data [4] or figure 5 and 6. The data is a result that starts from 3.6V battery and charges it until ascending theoretically preset 4.2V charge voltage with ±1% accuracy thus 4.158V. Experimentally a 4.145V measured. When the bat pin approaches the final float voltage (4.2V), the SE9016 enters constant-voltage mode and the charge current begins to decrease. We can realize it needs 16.8 hrs from 3.6V to 4.2V.

Figure 5

Figure 6

There’s a voltage called “overdischarge protect/preventing voltage” for lithium-based battery. After measured Ben’s descendant voltage during its discharging, a 2.3V measured then battery inside turn off its output voltage to 0V. This is within its specification 2.25~2.35V. So can let Ben’s SE9016 acted as following figure.

Figure 7

Once VBAT > 2.8V and VPROG > 100mV, SE9016 charges as next figure which is stated in CC/CV mode.

Figure 8

Now let Ben entered to POWER OFF mode to keep the RPROG equaled to 2 KΩ. (R14//R15. see figure 2). From the measured data [4] or figure 9 and 10. The data is a result that starts from 3.2V battery and charges it until ascending preset 4.2V charge voltage with ±1% accuracy thus 4.158V. Experimentally a 4.135V measured. It needs 2.68 hrs from 3.2V to 4.135V. Afterwards, SE9016 enters constant-voltage (CV) mode and the current begins to decrease. The plot of figure 7 & 8 doesn’t include data of CV mode.

Figure 9

Figure 10

The standby mode of SE9016 didn’t experiment. Also see figure 8 in blue flow. To manually restart a charge cycle when in standby mode, the input voltage ( usb power ) must be removed and reapplied or the charger must be shut down and restarted using the PROG pin.

This result of experiment may be based on unique battery applied and referenced. You can also find this standard battery technology in many other devices. Ben batteries share the characteristics common to lithium-based technology in other devices. Like other rechargeable batteries, these batteries may eventually require replacement.

[1]http://downloads.qi-hardware.com/hardware/qi_avt2/v1.0/datasheet/U1~Jz4720_ds.pdf
[2]http://downloads.qi-hardware.com/hardware/qi_avt2/v1.0/datasheet/U5~SE9016.pdf
[3]http://downloads.qi-hardware.com/hardware/qi_avt2/v1.0/datasheet/U7~BL8506-30NRM.pdf
[4]http://downloads.qi-hardware.com/hardware/qi_lb60/report/charge_cycle/data.ods
[5]http://www.mpoweruk.com/chargers.htm#rates
[6]鋰電池的守護神---鋰電池保護IC的重要性

Author: mailto:adam@qi-hardware.com