1- to 3-Cell, High-Current, Low-Noise,
Step-Up DC-DC Converters with Linear Regulator
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2, T
A
= +25°C, unless otherwise noted.)
LINEAR-REGULATOR POWER-SUPPLY
REJECTION RATIO vs. FREQUENCY
MAX1705/6 TOC10
MAX1705/MAX1706
LINEAR-REGULATOR
REGION OF STABLE C6 ESR
vs. LOAD CURRENT
C6 = 22µF
UNCOMPENSATED
C2 = 22pF (FEED FORWARD)
1
MAX1705/6 TOC11
60
50
40
30
20
10
0
100
1k
10k
100k
1M
100
10
C6 ESR (Ω)
PSRR (dB)
V
OUT
= 4V TO 5V
V
LDO
= 3.3V
I
LDO
= 200mA
C5 = 0.33µF
10M
STABLE REGION
0.1
0
1
50
100
150
200
250
300
FREQUENCY (Hz)
MAX1705
NOISE SPECTRUM AT POUT
(V
OUT
= 4.5V, V
IN
= 1.2V, 200mA LOAD)
LOAD CURRENT (mA)
NOISE (5mV
RMS/
div)
0V
1k
10k
100k
FREQUENCY (Hz)
1M
10M
MAX1705
LINEAR-REGULATOR OUTPUT NOISE SPECTRUM
(V
LDO
= 3.3V, V
OUT
= 4.5V, V
IN
= 1.2V, I
LDO
= 200mA)
MAX1705/6 TOC14
NOISE (50µV/div)
0V
1k
10k
100k
FREQUENCY (Hz)
1M
10M
_______________________________________________________________________________________
MAX1705/6 TOC13
7
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
