PQ30RV21 datasheet(7/8 Pages) SHARP

7 / 8 page

Low Power-Loss Voltage Regulators

PQ30RV1/PQ30RV11/PQ30RV2/PQ30RV21

¡ON/OFF operation is available by mounting externally D2 and R3.

¡When VADJ is forcibly raised above Vref (1.25V TYP) by applying the external signal, the output is turned off (pass transistor of

regulator is turned off). When the output is OFF, VADJ must be higher then Vref MAX., and at the same time must be lower than

maximum rating 7V.

In OFF-state, the load current flows to RL from VADJ through R2. Therefore the value of R2 must be as high as possible.

¡VO'=VADJ X RL/(RL+R2)

occurs at the load. OFF-state equivalent circuit R1 up to 10

Ω is allowed. Select as high value of RL and R2 as possible in this range.

In some case, as output voltage is getting lower (VO<1V) , impedance of load resistance rises. In such condition, it is sometime

impossible to obtain the minimum value of VO'. So add the dummy resistance indicated by RD in the figure to the circuit parallel to

the load.

s ON/OFF Operation

High : Output OFF

Low : Output ON

VADJ

CIN

VIN

Equivalent Circuit

in OFF-state

VO’

VADJ

s An Example of ON/OFF Circuit Using the 1-chip Microcomputer Output Port (PQ30RV1)

Output port of microcomputer

VOH (max) =0.5 V

VOH (min) =2.4 V (IOH=0.2mA)

MAX. rating of IOH=0.5mA

Output should be set as follows.

15.6V RL=52

Ω (IO=0.3A)

From VO=1.25V (1+R2/R1) we get VO=15.6V.

R2/R1=11.48

Assuming that VF(max)=0.8V for D2 in case of VOH(min)=2.4V, we get VADJ=VOH(min)-VF(max)=2.4V-0.8V=1.6V. From

Vref(max)=1.3V we get R3=0

Ω

If R1=10k

Ω, we get R2=11.48 X R1=114.8kΩ and IOH as follows, ingnoring RL (52 Ω) :

IOH=1.6V X (R1+R2) /R1 X R2

=1.6V X (10k

Ω+114.8k Ω) /10k Ω X 114.8k Ω=0.17mA

Hence, IOH<0.2mA. Therefore VOH(min)is ensured.

Next, assuming that VF(min) =0.5V for D2 in case of VOH(max), we get:

IOH=(5V-0.5V) (R1+R2) /R1 X R2=0.49mA which is less than the rating.

Figure 1 shows the VO-VC characteristics when R1=10k

Ω, R2=115kΩ, R3=0Ω, VIN=17V, RL=52Ω, and D1=1S2076A (Hitachi).

PQ30RV21 Datasheet(PDF) 7 Page - Sharp Corporation

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