High-Speed Step-Down Controller with

Accurate Current Limit for Notebook Computers

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5

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Minimum Off-Time

(Note 2)

500

ns

FB forced above the regulation point

800

µA

FB forced above the regulation point

5

µA

Quiescent Supply Current (V+)

Measured at V+

40

µA

SHDN = GND

5

µA

SHDN = GND

5

µA

Shutdown Supply Current (V+)

5

µA

Reference Voltage

1.98

2.02

V

Overvoltage Trip Threshold

(Fixed-Threshold Mode)

With respect to error comparator threshold, no load

OVP = GND, rising edge, hysteresis = 1%

12

17

%

External feedback, measured at FB with respect to

-30

+30

mV

Overvoltage Comparator Offset

(Adjustable-Threshold Mode)

Internal feedback, measured at OUT with respect to the

-3.5

+3.5

%

PGOOD Trip Threshold (Lower)

With respect to error comparator threshold, no load

OUT falling edge, hysteresis = 1%

-12.5

-7.5

%

PGOOD Trip Threshold (Upper)

With respect to error comparator threshold, no load

OUT rising edge, hysteresis = 1%

7.5

12.5

%

PGOOD Output Low Voltage

0.4

V

PGOOD Leakage Current

High state, forced to 5.5V

1

µA

Current-Limit Threshold (Fixed)

85

115

mV

35

65

Current-Limit Threshold

(Adjustable)

160

240

mV

Lockout Threshold

Rising edge, hysteresis = 20mV,

PWM disabled below this level

4.1

4.4

V

Logic Input High Voltage

LATCH, SHDN, SKIP

2.4

V

Logic Input Low Voltage

LATCH, SHDN, SKIP

0.8

V

Logic Input Current

LATCH, SHDN, SKIP

-1

1

µA

ELECTRICAL CHARACTERISTICS (continued)

°C to +85°C, unless otherwise noted.) (Note 3)

Note 1: When the inductor is in continuous conduction, the output voltage will have a DC regulation level higher than the error com-

parator threshold by 50% of the ripple. In discontinuous conduction (SKIP = GND, light load), the output voltage will have a

DC regulation level higher than the trip level by approximately 1.5% due to slope compensation.

and a 250pF capacitor connected from DH to LX. Actual in-circuit times may differ due to MOSFET switching speeds.

Note 3: Specifications to -40°C are guaranteed by design, not production tested.

Note 4: Production testing limitations due to package handling require relaxed maximum on-resistance specifications for the QFN

package. The MAX1844EEP, MAX1844EGP, and MAX1844ETP contain the same die and the QFN package imposes no

additional resistance in-circuit.