ISL81601. High battery discharge current. Backup power supply system

Hi korg, 

I will get back to you in a while.

Regards,

Avinash Kumar

Hi korg,

Thank you for your query for ISL81601. Here is the detailed explanation of your design. 

The ISL81601 should be able to control the IQDH29NE2LM5ATMA1 MOSFETs, as these MOSFETs have a sufficiently low gate threshold voltage (Vgs(th)) and are designed for high-current applications. The ISL81601 provides gate drive voltages to the MOSFETs, and the IQDH29NE2LM5ATMA1 has a maximum Vgs rating of 16V. The gate drive voltage provided by the ISL81601 is typically 6-12V, which should be sufficient for driving the MOSFETs efficiently.

To handle charging and discharging the battery using the ISL81601 in your setup, the IC will operate in both buck and boost modes, depending on the voltage conditions. Here's how the charging and discharging will work:

1. Charging the Battery (Buck Mode)

When the input voltage (VIN = 12V) is higher than the battery voltage (VOUT = 14.8V nominal), the ISL81601 will operate in buck mode to reduce the input voltage and provide a regulated charging current to the battery. Since your task is to charge the battery at 2A, you'll configure the ISL81601 to limit the charging current to 2A. Here's how it works:

• Voltage Regulation: The ISL81601 will regulate the output voltage to slightly above the battery’s nominal voltage (e.g., 16.8V for a 4S Li-ion pack, which has a full charge voltage of 4.2V per cell). You can configure this using external resistors in the feedback loop.

• Current Limiting: You'll use current sensing (via a sense resistor or inductor DCR) to limit the charging current to 2A. The ISL81601 will control the duty cycle of the MOSFETs to maintain a steady current to the battery as it charges.

2. Discharging the Battery (Boost Mode)

When the battery is discharging and powering the load (e.g., your server), the ISL81601 will operate in boost mode since the battery voltage (nominal 14.8V) is lower than the input/output requirement of the server.

• High Current Discharge (up to 50A): During discharge, the ISL81601 will boost the battery voltage to supply the load. The discharge current (up to 50A) will depend on the power demand of the server and the voltage difference between the battery and the output. 

• Battery Protection: You may need to configure overcurrent protection and low-voltage cutoffs in the ISL81601 to prevent the battery from over-discharging or being damaged during high-current loads.

Kindly give me an update if you need further query on the same IC.

Regards,

Avinash Kumar

Hello Avinash Kumar! Thanks for your feedback.
In theory, I understand how the chip should work.
Tell me the following.

What kind of resistor divider is needed at the input (VIN) of the chip, for what voltage should it be rated?

What kind of resistor divider at the output (OUT) of the chip, for what voltage should it be rated?

At the input of the chip (according to the figure above), I have a 12V power supply and a load in the form of a server (motherboard).
On the output side (OUT) of the chip, a battery is installed (battery voltage from 10V to 16.8V).

The idea is as follows - when there is 12V voltage from the PSU, the motherboard works and the ISL81601 works - charging the battery.
when the 12V voltage from the power supply disappears, the motherboard should continue to work, the ISL81601 should discharge the battery from 16.8V to 10V - while the motherboard (the VIN side of the ISL81601 microcircuit) should receive a stable 12V.

I have attached a diagram of my device. Please take a look.ISL81601 Renesas SCH.PDF

Hi korg,

You have configured the input voltage feedback (FB_IN) pin with 10.7kΩ and 150kΩ resistors for a 12V input, and the output voltage feedback (FB_OUT) pin with 523kΩ and 26.3kΩ resistors for a 16.8V output. These values are correct as per Equation 5 and Equation 6 in the datasheet. Also use thin film, 1W, 1% tolerance resistors. 

When the voltage at the FB_IN pin drops below 0.8V, the controller switches to reverse operation. Additionally, the VIN feedback loop is disabled when the FB_IN pin voltage is below 0.3V or above 4.7V. The feedback loop is also disabled during DE mode and the soft-start phase.

As for the FB_OUT pin, when its voltage drops to 0.8V, the controller activates and operates in a peak current-controlled Buck-Boost mode when VIN−VOUT​ is less than 2V, and in Buck mode when VIN−VOUT is greater than 2V.

When supply voltage reduces the controller operates in reverse direction mode and will supply output voltage at 12V (set by FB_IN) pin.

The discharge rate of current is maximum 50A. So, select current sense resistors such that at 50A the converter goes to hiccup mode (see page 19).

If you have any further query, then please feel free to ask.

Thanks, and regards,

Avinash Kumar

Hello Avinash Kumar!
I need your help!
I can't get the ISL81601 mixed-signal circuit to work.
Tell me what signals I should look at on which pins/terminals.
I have disconnected all connections to the microcontroller and operational amplifiers. I have left only the BB chip and its feedback connections.

Hi Korg,

Please provide a detailed explanation of your query, including all jumper settings and DSO output images. This will help me better understand and assist you

Thanks, and regards,

Avinash Kumar

Hi Avinash Kumar
Here is what I have on the pins of the chip
EN (Pin 30) (C14/R20)= 3.3V
LG1 (Pin 22) (R45-VT8) - nothing
LG2 (Pin 19) (R63-VT9) - nothing
PH1 (Pin 24) (C30-R48) - nothing
PH2 (Pin 17) (C29-R60) - nothing
UG1 (Pin 25) (R44-VT7) - nothing
UG2 (Pin 16) (R62-VT10) - nothing
IMON_OUT (Pin 11) (KT4-R38) (IOUT_B) = 1.2V
IMON_IN (Pin 31) (R30) (IIN_B) = 5V (pull-up to 5V)
VDD_8V (Pin 20) (VCC8) = 7.8V
BT1 (Pin 23) (R33) = 8.9V because external LDO (R15) is connected
BT2 (Pin 18) (R34) = 8.9V because external LDO (R15) is connected
COMP (Pin 9) (C25/C28) – nothing
OVP (Pin 12) (KT3) = 0V.
BSTEN (Pin 1) (KT2/R24) = 4.8V
FB_IN (Pin 2) (R19/R16) = 4.6V (5V jumper present)

Transistors IQD005N04NM6ATMA1 (4 pcs) installed
Voltage dividers - 12V input (150k/10.7k) and 16.8V output (215k/10.7k)
Resistors R49 - 15kOhm installed (LG1 pin)
Resistor R30 is connected to a 5V source (IMON_IN pin) (input current protection is disabled)
Transistor VT6 (CLKOUT/DITHER) removed (not installed)
Resistors R50, R68, R69, R74, R75 not installed (connections to op amp and MK are disabled)
Resistors R39, R47, R56, R66 not installed (connections to I2C microcircuit current measurements are disabled)
LG2 pin 15kOhm R61 - not installed.
Capacitors C27, C32, C36, C39 are installed with a nominal value of 0.1 μF
on VIN 12 volts. The output should be 16.8 V

2148.ISL81601 Renesas SCH.PDF

This is on the gates of the lower transistors (LG1/LG2)
The microcircuit does not start

on the gates LG1.LG2 17 pulses