Rainbow Electronics MAX1885 - Manual (Page 9)

MAX1778/MAX1880–MAX1885
Quad-Output TFT LCD DC-DC
Converters with Buffer
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7.88
7.92
7.96
8.00
8.04
8.08
8.12
0 200 400 600 800
MAIN 8V OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1778 toc01
I OUT (mA)
V
OUT
(V)
V IN = 5V
R COMP = 24k Ω
C
COMP
= 470pF
V IN = 3.3V
C INTG = 470pF
40
50
60
70
80
90
100
0 200 400 600 800
MAIN 8V OUTPUT EFFICIENCY
vs. LOAD CURRENT
MAX1778 toc02
I OUT (mA)
EFFICIENCY (%)
V IN = 3.3V
V OUT = 8V
R COMP = 24k Ω
C COMP = 470pF
C INTG = 470pF
V IN = 5V
11.76
11.92
11.84
12.08
12.00
12.16
12.24
0 200 300 100 400 500 600
MAIN 12V OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1778 toc03
I OUT (mA)
V
OUT
(V)
FIGURE 8
C
INTG = 470pF
V
IN = 3.3V
V
IN = 5V
40
60
50
80
70
90
100
0 200 300 100 400 500 600
MAIN 12V OUTPUT EFFICIENCY
vs. LOAD CURRENT
MAX1778 toc04
I OUT (mA)
EFFICIENCY (%)
FIGURE 8
V
OUT = 12V
C INTG = 470pF
V
IN = 3.3V
V
IN = 5V
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
2.5 3.5 3.0 4.0 4.5 5.0 5.5
STEP UP CONVERTERS
SWITCHING FREQUENCY vs. INPUT VOLTAGE
MAX1778 toc05
V IN (V)
SWITCHING FREQUENCY (MHz)
MAX1778
19.2
19.4
19.8
19.6
20.0
20.2
POSITIVE CHARGE-PUMP OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1778 toc06
I POS (mA)
V
POS
(V)
0 10 5 15 20
V SUPP = 10V
V SUPP = 8V
V SUPP = 7.5V
V SUPP = 7V
30
80
70
90
100
POSITIVE CHARGE-PUMP EFFICIENCY
vs. LOAD CURRENT
MAX1778 toc07
I NEG (mA)
EFFICIENCY (%)
0 10 5 15 20
V POS = 20V
V SUPP = 7.5V
V SUPP = 7V
V SUPP = 8V
V SUPP = 10V
60
50
40
5
15
10
25
20
35
30
40
2 6 8 4 10 12 14
MAXIMUM POSITIVE CHARGE-PUMP
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
MAX1778 toc08
V SUPP (V)
V
POS
(V)
I POS = 10mA
I POS = 1mA
-5.04
-5.00
-5.02
-4.96
-4.98
-4.92
-4.94
-4.90
NEGATIVE CHARGE-PUMP OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1778 toc09
I
NEG
(mA)
V
NEG
(V)
0 10 20 30 40
V SUPN = 7V
V SUPN = 8V
V SUPN = 6V
Typical Operating Characteristics
(Circuit of Figure 1, V IN = +3.3V, SHDN = IN, V MAIN = V SUPP = V SUPN = V SUPB = V SUPL = 8V, BUF- = BUFOUT,
BUF+ = FLTSET = TGND = PGND = GND, T A = +25°C.)