4.5V to 28V Input, Synchronous PWM Buck Controllers

for DDR Termination and Point-of-Load Applications

6

_______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

PARAMETER

CONDITIONS

MIN

MAX

UNITS

REFERENCE

Reference Output Voltage

1.97

2.03

V

Reference Load Regulation

10

mV

Reference UVLO

1.5

1.7

V

VTTR

VTTR Output Voltage Range

0

1.8

V

49.5

50.5

49

51

VTTR Output Accuracy

49.5

50.5

SOFT-START

ILIM Ramp Period

Ramps the ILIM trip threshold from 20% to 100% in

20% increments

0.8

3.0

ms

Output Predischarge Period

Rising edge of EN/HSD to the start of internal digital

soft-start

0.8

3.0

ms

OSCILLATOR

FSEL = VL

2.18

2.83

FSEL unconnected

1.45

1.89

FSEL = REF

1.09

1.41

On-Time

(Note 2)

FSEL = GND

0.82

1.00

µs

FSEL = VL

0.89

1.16

FSEL unconnected

0.61

0.80

FSEL = REF

0.43

0.56

On-Time

(Note 2)

FSEL = GND

0.33

0.41

µs

Off-Time

(Note 2)

420

ns

CURRENT LIMIT

LX to PGND, ILIM = VL

80

115

Ω

30

65

Current-Limit Threshold (Positive

Direction)

Ω

150

230

mV

Current-Limit Threshold (Negative

Direction)

LX to PGND, ILIM = VL, with respect to positive

current-limit threshold

-130

-90

%

ILIM Input Current

µA

FAULT DETECTION

57

63

%

≤ +1V)

0.576

0.624

Overvoltage Threshold

MAX8554

0.696

0.744

V

VL REGULATOR

Output Voltage

4.80

5.33

V

RMS Output Current

35

mA

Bypass Capacitor

ESR < 100m

Ω

2.2

µF