My MAX17599 circuit is designed based on MAXREFDES48#, and there’s a resistor R16 from pin VDRV to CS in the MAXREFDES48# schematic, how to choose the value for this resistor?

Q: The MAX17599 circuit is designed based on MAXREFDES48#, and there’s a resistor R16 from pin VDRV to CS in the MAXREFDES48# schematic as shown below.The output of MAX17599 is interrupt during hot-swap at the load. It was measured over current project during the issue. How to modify the circuit & want to know how to choose this resistor? Is there a formula to calculate the value of this resistor? A: The purpose of the resistor R16 is to apply a DC bias to the CS pin so that the voltage on the current resistor R18 is reduced for a certain desired peak current limit. This allows the power dissipation of the R18 resistor to be reduced and improve efficiency. Please see the formulas to calculate for the resistors R16 and R18 below. The resistor, R17 and capacitor, C11 are always selected at 220 Ω and 1000pF respectively . VR18max can be chosen value between 290mV and 150mV. , where R17=220Ω, C11=1000pF, 290mV≥VR18max≥150mV For example, you calculate the maximum primary peak current, Ipeak_max equal 5A and select VR18max=150mA. The R16 and R18 are calculated as table below: R16(Ω) R18(Ω) VR18max(V) Vcs-peak(V) VDRV(V) R17(Ω) C119pF) Ipeakmax(A) 7401.4 0.03 0.15 0.29 5 220 1000 5

How to choose the resistor from VDRV to CS to set the current-limit protection threshold?

The purpose of the resistor between VDRV and CS is to apply a DC bias to the CS pin so that the voltage on the current resistor is reduced for a certain desired peak current limit. This allows the power dissipation of the current resistor to be reduced and improve efficiency . Below is part of the MAX17599 schematic . The resistor, R17 and capacitor, C11 are always selected at 220Ω and 1000pF respectively. VR18max can be chosen value between 290mV and 150mV . Below is the formula that calculates R16 and R18. For example, you calculate the maximum primary peak current, Ipeak_max equal 5A and select VR18max=150mA. The R16 and R18 are calculated as table below. R16(Ω) R18(Ω) VR18max(V) Vcs-peak(V) VDRV(V) R17(Ω) C119pF) Ipeakmax(A) 7401.4 0.03 0.15 0.29 5 220 1000 5

What is the frequency jitter range of the MAX17599? What is the risk if we surpass this range?

MAX17599's frequency jitter range is ±10%. It is not recommended to surpass this range. When you do, it is possible to cause issues such as additional ripple voltage, lower efficiency, and other problems.

When testing a 5V@6A isolated power supply designed with the MAX17599 power IC, we found that during power-on, the output voltage rise time was only 200-300us. Such a short rise time can cause the load to go into lockout. We hope that you can provide a sol

As shown in the figure below, in the feedback circuit, the value of resistor R17 from pin 3 of the photocoupler to ground will affect the rise time of the output voltage; The larger the resistance, the longer the output voltage rise time. If the resistor is changed to 470 ohms, the output voltage rise time becomes approximately 3ms.

How do you modify the MAXREFDES48# output to 24V/2A?

Please refer to the design of MAXREFDES48# as follows to attain an output of 24V/2A. 1. Transformer T1: Use HanRun's HR102302 2. Inductor L1: Use Coilcraft's SER1390-473ML 3. Change C12 to 22nF, for example GRM31BR72D223KW01# 4. For C1 use three 10uF capacitors. 5. C17,C19,C20,C23: Use 10uF, for example GRM32EB31H106KA12# 6. N2,N3: Use SiSS40DN 7. R32: Use 550 kohm 8. R31: Use 3.5 kOhm 9. Remove C16, R20, R25, R35. By implementing the modifications above, the output voltage of the reference design can be changed to 24V and the load efficiency at 2A can reach 94%.

Is it possible to connect an external 10V power supply to pin VDRV on part number MAX17599?

This is not recommended since the absolute maximum rating of pin V DRV on part number MAX17599 is +6V. If you wish to have a higher FET gate voltage you should consider using an external FET driver like MAX4420

For MAX17598 can the VIN Bootstrap UVLO Wakeup thresholds be changed from a typical value of 20V to a typical value somewhere between 7.8V and 8.8V?

The answer is NO; V IN Bootstrap UVLO Wakeup thresholds are fixed internally in the IC. However, MAX17599 has a lower V IN Bootstrap UVLO Wakeup threshold typically 7V

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