Part Number: LM2596
Hello,
I am trying to determine whether the DS3502 I²C digital potentiometer can be used to control the output voltage of an LM2596 adjustable buck regulator by replacing the traditional feedback resistor (R2) shown in the TI datasheet Figure 9-13.
VOUT=VREF(1+R2R1),VREF=1.23 VV_{OUT} = V_{REF}\left(1 + \frac{R2}{R1}\right), \quad V_{REF}=1.23\text{ V}VOUT=VREF(1+R1R2),VREF=1.23 V
I attempted to replace R2 (VOUT - FB) with the DS3502, keeping R1 = 1 k ohm from FB → GND.
The DS3502 is powered with:
V+ (analog) = 12 V
VCC (logic) = 3.3 V
RH → VOUT,
RW → FB,
RL not used,
I2C verified working (resistance changes 2 k ohm , 6.6 k ohm , 11.6 k ohm when sweeping wiper).
When disconnected from the circuit, the DS3502 behaves correctly.
However, when connected to the LM2596 feedback pin, the output voltage remains almost constant (around 11.5–11.8 V) regardless of wiper setting.
My question:
Is the DS3502 electrically suitable for use as the R2 variable top resistor in the LM2596 feedback network?
Are there internal limitations (compliance voltage, wiper linearity, FET structure, minimum V+-to-terminal voltage, leakage, etc.) that would prevent the LM2596 from regulating correctly when R2 is replaced by the DS3502?
If the DS3502 cannot be used in this topology, is there a recommended digital potentiometer or digital method for controlling the LM2596 feedback pin?
Any clarification would be appreciated.
Thank you!
