Typical operating characteristics, Electrical characteristics (continued) – Rainbow Electronics MAX1843 User Manual
Page 4
Typical Operating Characteristics
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
0.001
0.01
0.1
1
10
EFFICIENCY vs. OUTPUT CURRENT
(V
IN
= +5.0V, L = 2.5
µH)
MAX1843 toc03
OUTPUT CURRENT (A)
V
OUT
= +1.5V, R
TOFF
= 1OOk
Ω,
f
PWM
= 770kHz
V
OUT
= +1.8V, R
TOFF
= 75k
Ω,
f
PWM
= 910kHz
V
OUT
= +2.5V, R
TOFF
= 47k
Ω,
f
PWM
= 1070kHz
100
95
90
85
80
70
65
60
55
50
75
EFFICIENCY (%)
0.001
0.01
0.1
1
10
EFFICIENCY vs. OUTPUT CURRENT
(V
IN
= +3.3V, L = 1.5
µH)
MAX1843 toc04
OUTPUT CURRENT (A)
V
OUT
= +2.5V, R
TOFF
= 56k
Ω,
f
PWM
= 1000kHz
V
OUT
= +2.5V, R
TOFF
= 39k
Ω,
f
PWM
= 610kHz
V
OUT
= +1.8V, R
TOFF
= 43k
Ω,
f
PWM
= 1050kHz
100
95
90
85
80
70
65
60
55
50
75
EFFICIENCY (%)
0.001
0.01
0.1
1
10
EFFICIENCY vs. OUTPUT CURRENT
(f
PWM
= 270kHz)
MAX1843 toc05
I
OUT
(A)
V
IN
= +3.3V, V
OUT
= +1.8V,
L = 4.7
µH, R
TOFF
= 160k
Ω
100
95
90
85
80
70
65
60
55
50
75
EFFICIENCY (%)
V
IN
= +5V, V
OUT
= +1.8V, L = 5.6
µH,
R
TOFF
= 240k
Ω
NORMALIZED OUTPUT ERROR
vs. OUTPUT CURRENT
MAX1843 toc06
0.001
0.01
0.1
1
10
OUTPUT CURRENT (A)
V
IN
= +3.3V, V
OUT
= +1.5V, L = 1.5
µH
V
IN
= +5V, V
OUT
= +1.5V, L = 2.5
µH
0.1
0
-0.1
-0.2
-0.3
-0.4
NORMALIZED OUTPUT ERROR (%)
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
V
IN
= +4.5V
150
NMOS Switch On-Resistance
R
ON,N
I
LX
= 0.5A
V
IN
= +3V
200
m
Ω
Current-Limit Threshold
I
LIMIT
2.9
4.3
A
Idle-Mode Current Threshold
0.2
1.0
A
No-Load Supply Current
I
IN
+ I
CC
V
FB
= 1.2V
600
µA
FB Input Bias Current
I
FB
V
FB
= 1.2V
0
300
nA
Off-Time
t
OFF
R
TOFF
= 110k
Ω
0.85
1.15
µs
MAX1843
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN Package
4
_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(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.