ADPL74101 datasheet(31/49 Pages) AD

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Data Sheet

ADPL74101

analog.com

Rev. 0

31 of 49

Setting the Output Voltage

The ADPL74101 output voltages are set by an external feedback resistor divider carefully placed across the output,

as shown in Figure 34 and Figure 35. The regulated output voltage is determined by Equation 16, as follows:

VOUT = 0.8V(1 +

)

(16)

Place the RA and RB resistors close to the VFB pin to minimize PCB trace length and noise on the sensitive VFB node.

Take care to route the VFB trace away from noise sources, such as the inductor or the SW trace. To improve frequency

response, a feedforward capacitor (CFF) can be used.

The ADPL74101 can be programmed to a fixed 12V or 5V output via the VPRG pin. Figure 35 shows how the VFB pin is

used to sense the output voltage in fixed output mode. Tying VPRG to INTVCC or GND programs, VOUT to 12V or 5V,

respectively. Floating VPRG sets VOUT to an adjustable output mode using external resistors.

Figure 34. Setting Adjustable Output Voltage

Figure 35. Setting Fixed 12V or 5V Output Voltage

RUN Pin and Undervoltage Lockout

The ADPL74101 is enabled using the RUN pin. The RUN pin has a rising threshold of 1.2V with 100mV of hysteresis.

Pulling the RUN pin below 1.08V shuts down the main control loop and resets the soft-start. Pulling the RUN pin

below 0.7V disables the controller and most internal circuits, including the INTVCC LDO regulators. In this state, the

ADPL74101 draws only ≈1μA of quiescent current.

The RUN pin is high impedance; it must be externally pulled up or pulled down, and is driven directly by logic. The

RUN pin can tolerate up to 100V (the absolute maximum). Therefore, the pin can be conveniently tied to VIN in always-

on applications where the controller is enabled continuously and never shuts down. Do not float the RUN pin.

The RUN pin can also be configured as a precise UVLO on the input supply with a resistor divider from VIN to GND, as

shown in Figure 36.

Figure 36. Using the Run Pin as UVLO

ADPL74101

VFB

CFF

VOUT

ADPL74101

VFB

INTVCC/GND

VPRG

COUT

VOUT

12V/5V

ADPL74101

RUN

VIN

ADPL74101 Datasheet(PDF) 31 Page - Analog Devices

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