Rainbow-electronics MAX1844 Uživatelský manuál stáhnout pdf (Strana 3)

MAX1844

High-Speed Step-Down Controller with

Accurate Current Limit for Notebook Computers

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, V+ = 15V, V

= V

= 5V, SKIP = GND, T

= 0°C to +85°C, unless otherwise noted. Typical values are at

= +25°C.)

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

REF Sink Current

REF in regulation

µA

REF Fault Lockout Voltage

Falling edge, hysteresis = 40mV

1.6

Overvoltage Trip Threshold

(Fixed-Threshold Mode)

With respect to error comparator threshold, no load

OVP = GND, rising edge, hysteresis = 1%

14.5

External feedback, measured at FB with respect to

OVP

, 1V < V

OVP

< 1.8V, rising edge, hysteresis =1%

-30

+30

Overvoltage Comparator Offset

(Adjustable-Threshold Mode)

Internal feedback, measured at OUT with respect to the

nominal OUT regulation voltage, 1V < V

OVP

< 1.8V,

rising edge, hysteresis = 1%

-3.5

+3.5

OVP Input Leakage Current

1V < V

OVP

< 1.8V

-100

+100

Overvoltage Fault

Propagation Delay

FB forced 2% above trip threshold

1.5

µs

Output Undervoltage Protection

Trip Threshold (Fixed-Threshold

Mode)

With respect to error comparator threshold, UVP = V

External feedback, measured at FB with respect to

UVP

0.4V < V

UVP

< 1V

-40

+40

Output Undervoltage Protection

Trip Threshold (Adjustable-

Threshold Mode)

Internal feedback, measured at OUT with respect to the

nominal OUT regulation voltage, 0.4V < V

UVP

< 1V

-5

UVP Input Leakage Current

0.4V < V

UVP

< 1V

-100

+100

Output Undervoltage Protection

Blanking Time

From rising edge of SHDN

PGOOD Trip Threshold (Lower)

With respect to error comparator threshold, no load

-12.5

-10

-8

PGOOD Trip Threshold (Upper)

With respect to error comparator threshold, no load

12.5

PGOOD Propagation Delay

FB forced 2% beyond PGOOD trip threshold, falling

µs

PGOOD Output Low Voltage

SINK

= 1mA

0.4

PGOOD Leakage Current

High state, forced to 5.5V

µA

ILIM Adjustment Range

0.25

Current-Limit Threshold (Fixed)

GND - V

, ILIM = V

100

110

ILIM

= 0.5V

Current-Limit Threshold

(Adjustable)

GND - V

ILIM

= 2V

170

200

230

Current-Limit Threshold

(Negative Direction)

GND - V

, SKIP = V

, ILIM = V

= +25°C

-140

-117

-95

Current-Limit Threshold

(Zero Crossing)

GND - V

CS,

SKIP = GND

Thermal Shutdown Threshold

Hysteresis = 10°C

150

°C

Undervoltage

Lockout Threshold

Rising edge, hysteresis = 20mV,

PWM disabled below this level

4.1

4.4

1 2 3 4 5 6 7 8 ... 22 23

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