UPC1933GR Просмотр технического описания (PDF) - NEC => Renesas Technology

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UPC1933GR

DC-DC CONVERTER CONTROL IC

NEC => Renesas Technology 

µ PC1933

3. NOTES ON USE

3.1 Setting the Output Voltage

Figure 3-1 illustrates the method of setting the output voltage. The output voltage is obtained using the formula shown in

the figure.

The input threshold value of the error amplifier is 0.3 V (TYP.) for the error amplifier. Therefore, select a resistor value

that gives this voltage.

Figure 3-1 Setting the Output Voltage

VOUT (positive voltage)

VOUT =

1 + R1

R2

• 0.3

R1

1

R2

CNF

RNF

8

E/A

0.3 V

3.2 Setting the Oscillation Frequency

Choose RT according to the oscillation frequency (fOSC) vs timing resistor (RT) characteristics (refer to Typical

Characteristics Curves fOSC vs RT.) The formula below (3-1) gives an approximation of fOSC. However, the result of

formula 3-1 is only an approximation, and the value must be confirmed in actual operation, especially for high-frequency

operation.

fOSC[Hz] ≅ 1.856 x 109/RT[Ω]

(3-1)

3.3 Preventing Malfunction of the Timer Latch-Method Short Circuit Protection Circuit

The timer latch short-circuit protection circuit operates when the error amplifier output (pin 8) exceed approximately 1.92

V, and cuts off the output. However, if the rise of the power supply voltage is fast, or if there is noise on the DLY pin (pin 2),

the latch circuit may malfunction and cut the output off.

To prevent this, lower the wiring impedance between the DLY pin and the GND pin (pin 6), and avoid applying noise to

the DLY pin.

Data Sheet G13690EJ3V0DS00

13

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