Adjustable, Step-Down,

Current-Mode PWM Regulators

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11

OUTPUT

5V

MAX750A: 4.0V TO 11.0V

MAX758A: 4.0V TO 16.0V

LX

CC

GND

SS

MAX750A

MAX758A

SHDN

V+

REF

L1

*

I.C.

1

3

7

5

4

62

C6

0.01µF

C2

1µF

C3

*

D1

IN5817

C5

330pF

R3

13.0k

C4

*

8

R1

510k

C1

0.1µF

FILTER

OUTPUT

L2

25µF

C7

2.2µF

OUTPUT

OPTIONAL LOWPASS OUTPUT FILTER

INPUT SUPPLY RANGE

(V)

6.0 to 11.0

6.0 to 16.0

10.2 to 16.0

PART

MAX750A

MAX758A

GUARANTEED OUTPUT CURRENT AT 5V OUTPUT

(mA)

450

450

750

NOTE: PIN NUMBERS REFER TO 8-PIN PACKAGES.

R2

40.2k

Figure 3. Standard Step-Down Circuit

and GND pins as possible. Also, place the output

capacitor as close to the inductor and the GND pin as

possible. The traces connecting the input and output

filter capacitors and the catch diode must be short to

minimize inductance and capacitance. For this reason,

avoid using sockets, and solder the IC directly to the

PC board. Use an uninterrupted ground plane if possi-

ble; otherwise, use a star ground connection.

Output-Ripple Filtering

A simple lowpass pi-filter (Figure 3) can be added to

the output to reduce output ripple to about 5mVp-p.

The cutoff frequency with the values shown is 21kHz.

Since the filter inductor is in series with the circuit out-

put, its resistance should be kept to a minimum so the

voltage drop across it is not excessive.