For the MAX1928:

Resistors R1 and R2 are external to the MAX1927 (see

250µS for the MAX1927. See the Electrical Characteristics

cel out the dominant pole created by the output

load and the output capacitance:

5) Calculate the high-frequency compensation pole to

cancel the zero created by the output capacitor’s ESR:

1

2

1

2

ππ

××

=

××

RC

R

C

ESR

OUT

C

f

R

RC

C

C

L

OUT

C

=

×

1

2

1

2

ππ

××

=

××

RC

R

C

L

OUT

C

C

R

V

I

L

OUT

OUT MAX

=

()

C

V

IR

g

f

C

OUT

OUT MAX

CS

m

C

=











 ×









×









()

11

2

π

Low-Output-Voltage, 800mA, PWM Step-Down

DC-DC Converters

10

______________________________________________________________________________________

BATT

COMP

GND

REF

PGND

LX

POK

FB

2.6V TO 5.5V

C1

10

µF

C2

10

µF

1200pF

18k

Ω

L1

CDRH4D18

4.7

µH

1.8V AT 800mA

SHDN

PWM

MAX1928-18

22pF

C3

0.1

µF

Figure 3. Applications Circuit for the MAX1928

BATT

COMP

REF

PGND

LX

POK

FB

2.6V TO 5.5V

C1

10

µF

C2

10

µF

680pF

15k

Ω

L1

CDRH4D18

4.7

µH

1V AT 800mA

SHDN

MAX1927R

22pF

C3

0.1

µF

R1

16.5k

Ω

1%

R2

49.9k

Ω

1%

GND

PWM

Figure 4. Applications Circuit for the MAX1927