Rainbow-electronics MAX1644 Uživatelský manuál Strana 3

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MAX1644
2A, Low-Voltage, Step-Down Regulator with
Synchronous Rectification and Internal Switches
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
CC
= +3.3V, FBSEL = GND, T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
ELECTRICAL CHARACTERISTICS
(V
IN
= V
CC
= +3.3V, FBSEL = GND, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 3)
Note 2: Recommended operating frequency, not production tested.
Note 3: Specifications from 0°C to -40°C are guaranteed by design, not production tested.
R
TOFF
= 150k
V
FB
= 1.2V
V
FB
= 1.2V
I
LX
= 0.5A
V
IN
= 3.0V to 5.5V, I
LOAD
= 0,
FBSEL = GND or REF
I
LX
= 0.5A
CONDITIONS
µs1.03 1.63t
OFF
Off-Time Default Period
nA0 250I
FB
FB Input Bias Current
µA360I
IN
+ I
CC
No-Load Supply Current
A0.2 0.7I
IM
Idle Mode Current
Threshold
A2.3 3.5I
LIMIT
Current-Limit Threshold
m
200
R
ON, P
PMOS Switch
On-Resistance
m
150
200
R
ON, N
2.48 2.57
3.276 3.390
V3.0 5.5V
IN
Input Voltage
V1.08 1.12V
REF
Reference Voltage
VV
REF
V
IN
Adjustable Output Voltage
1.08 1.12
UNITSMIN TYP MAXSYMBOLPARAMETER
V
IN
= V
CC
= 4V to 5.5V,
FBSEL = unconnected
V
IN
= 3V to 5.5V, FBSEL = V
CC
V
IN
= 3V to 5.5V, FBSEL = REF
V
IN
= 4.5V
V
IN
= 3V
NMOS Switch
On-Resistance
150V
IN
= 4.5V
V
IN
= 3V
V
I
LOAD
= 0 to 2A,
V
FB
= V
OUT
V
OUT
Preset Output Voltage
Maximum Output RMS
Current
A
RMS
SS Sink Current I
SS
100 µA
SHDN Input Current
I
SHDN
-0.5 0.5 µA
SS Source Current I
SS
3.5 5 6.5 µA
SHDN Input Low Threshold
V
IL
0.8 V
SHDN Input High Threshold
V
IH
2.0 V
FBSEL Input Current -5 +5 µA
0.9 1.3
5.8
V
SS
= 1V
V
SHDN
= 0 to V
CC
FBSEL = REF
PARAMETER SYMBOL MIN TYP MAX UNITS
Undervoltage Lockout
Threshold
V
UVLO
2.5 2.6 2.7 V
FB Input Bias Current I
FB
0 80 200 nA
t
OFF
1.13 1.33 1.53
0.20 0.33
Off-Time Start-Up Period t
OFF
4 · t
OFF
µs
On-Time Period t
ON
0.4 µs
CONDITIONS
V
FB
= 1.2V
R
TOFF
= 150k
R
TOFF
= 30.1k
V
IN
falling, hysteresis = 40mV
FB = GND
Off-Time Default Period
4.3 5.6
µs
R
TOFF
= 499k
FBSEL Logic Thresholds
0.2
V
FBSEL = GND
0.7 · V
CC
0.7 · V
CC
- 0.2 + 0.2
FBSEL = unconnected
V
CC
- 0.2FBSEL = V
CC
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