ISL81601. High battery discharge current. Backup power supply system

ISL81601. High battery discharge current. Backup power supply system.

Hello!
I have developed a printed circuit board based on ISL81601 with powerful transistors IQDH29NE2LM5ATMA1 (MOSFET N-CH 25V 75A PG-TSON-8) and a powerful choke IHDM1008BCEV1R2M3A (FIXED IND 1.2UH 80A 0.3 MOHM Unshielded TH).
At the input (VIN) of ISL81601, the system voltage (power supply) is 12V and the load is a server.
At the output (VOUT) of ISL81601, the Battery is 4S7P (Nominal Voltage 14.8V)
My task is to charge the battery (current 2A) and discharge the battery (current up to 50A).
Tell me, how to understand, will ISL81601 be able to control IQDH29NE2LM5ATMA1 transistors?
I have provided power supply for the internal LDO from the EXTBIAS pin on the board.

Parents
  • 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

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

  • Hi Korg,

    Thank you for providing the data on the ISL81601 circuit. Based on the information:

    1. No Switching on PH1/PH2, UG1/UG2, LG1/LG2:

      • Issue: This indicates that the control loop is not functioning.
      • Solution: Check the COMP pin (Pin 9) for proper compensation network configuration. No signal here means the control loop isn’t driving the MOSFETs.
      • Also, verify that the feedback network on FB_IN (Pin 2) is set correctly—4.6V is too high and suggests incorrect feedback configuration.  Ideally it should be around 0.8 volts. Also check whether this high voltage might have also damaged the IC also.                                                                                
    2. OVP Pin (0V):

      • Issue: Indicates a possible overvoltage protection trigger.
      • Solution: Verify the resistor divider network for the output and ensure the feedback voltage is not exceeding the regulation point, which could cause the IC to enter protection mode.       

    Thanks, and regards,

    Avinash Kumar

  • Hello! Avinash Kumar
    I checked the resistive dividers IN and OUT. I applied 12V (IN) (pin 2) and 16.8V (OUT) (pin 10) to them; the levels at the ISL81601 pins were 0.8V.
    I looked at the SS /TRK pin (pin 8) with an oscilloscope - it constantly shows 0V when EN (pin 30) is applied to the ISL81601.
    Please tell me how to understand that the ISL81601 is ready for operation? Which pin should I look at?

  • Hello! Avinash Kumar
    Please tell me the minimum required set of elements that need to be installed to launch ISL80601?
    What protections can be disabled to get a minimum launch.

Reply Children
  • Hello! Avinash Kumar
    What I noticed... I had 3 ISL81601 chips soldered. In each chip, only the LDO worked.

    Can you tell me if the LDO blocks are enable? Or do the LDOs turn on regardless of the operation of the other blocks of the chip?

  • Hi Korg,

    Thanks for the update. Based on the information provided by you, here are some suggestions.

    1.  If the Soft Start/Tracking pin constantly shows 0V, it suggests that the chip is not entering its soft-start sequence. The SS/TRK pin should rise gradually when the device is enabled. If it remains at 0V, it indicates that the device is not progressing to operational mode, likely due to fault conditions.                                                                                                                                                 
    2. To confirm the ISL81601 is ready for operation, check the following:

      • EN (Pin 30) should be high (>1.8V).
      • SS/TRK (Pin 8) should rise from 0V during startup. If it stays at 0V, the IC isn’t entering soft-start, likely due to a fault condition (e.g., OVP or current protection).
      • PGOOD (Pin 13) should be high if the output voltage is within regulation.
                                                                                                                                     
    3. You can disable overcurrent protection by adjusting the sense resistor or temporarily bypassing current sense to test basic functionality and temporarily avoid connecting the OVP circuit. To test without overvoltage protection put the OVP pin (Pin 12) directly to ground, which ensures that it remains in the "low" state. This prevents the OVP comparator from detecting an overvoltage condition and triggering the protection circuitry. How ever this is not recommended.                                                                                                                                                       
    4. The LDO operates independently of the switching control. It remains active when VDD or EXTBIAS is supplied, even if switching is disabled due to a fault condition. Please refer to sec 5.2 page 26 of the data sheet.

    Thanks, and regards,

    Avinash Kumar

  • Hello! Thanks for your help!
    I made another board, found an error in connecting the output current sensor. Now I have a launch of the chip.
    I am trying to find the optimal parameters for the 16.8V output in the forward direction. My goal is to get a working current of 50A.
    Transistors IQD005N04NM6ATMA1 Infineon N-CH 40V 58A
    Choke IHDM1008BCEV1R2M3A Vishay
    If you can simulate such a bundle to get the optimal result - please help.

  • Thanks for your help.
    I started testing the board.
    Battery charging with 5A current is going well. CC mode.
    I tried working with a 15A load. Input 12V output 16.8V (15A). Transistors (IQD005N04NM6ATMA1) get very hot. Output capacitor gets very hot.

  • Here is the battery charge with a current of 5A (16.8V - the output divider is set). CC mode. Here is the battery charge with a current of 5A (16.8V - the output divider is configured). CC mode.
    Here the drivers of the ISL 81601 microcircuit (pin 18 to 23) are powered from an external LDO source. 8V (1A) to reduce the heating of the ISL81601 microcircuit

  • Then I turned on the ISL81601 in the opposite direction. Battery discharge current 8A. On load 12V current 10A.
    The ILS81601 microcircuit heats up a lot - temperature 51°C.

    Then the battery discharge current is 18A. Load 12V - current 20A.
    The temperature of the ISL81601 is approximately 53°C. The temperature of the transistors is 60°C. After 10 minutes of operation at a current of 20A - the output drops to 4V.

  • Hello Kumar!
    Please tell me, why does the current protection work?
    Working from the battery (at the output) to the load (load at the input).
    When the current reaches 20A, the voltage in the load drops to ~4V. Cooling and restarting the ISL81601 saves.
    The first time, the IMON IN resistor was 42.2 kOhm.
    Then a 36 kOhm resistor was installed = R=36 kOhm = the microcircuit resets the voltage when the current reaches 20A. What else can affect it?