Rainbow Electronics MAX863 - Manual (Page 8)

MAX863
Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
8 _______________________________________________________________________________________
MAX863
EXT2
CS2
V OUT2 = 12V V OUT1 = 5V
V IN = 2.7V TO THE LOWER OF V OUT1 OR V OUT2
N1.B
IRF7301
C7
0.1
µF
R4
115k
1% C8
82pF
C6
10pF
1M
C5
100
µF
20V
≤0.1Ω
R2
50m Ω
R3
1M
1%
N1.A
R1
50m
Ω
R7
100k
C1
220 µF
10V
≤0.1Ω
R5
R6
D1
MBRS340T3 D2
MBRS340T3
L1
10
µH
2A
L2
10
µH
2A
C3
100 µF
10V
≤0.1Ω
C4
100 µF
10V
≤0.1Ω
C2
0.1
µF
ON/OFF
FB2
SHDN1
EXT1
CS1
LBO
LOW-BATTERY
DETECTOR OUTPUT
LBI
SENSE1
PGND
V DD
GND FB1
SHDN2
REF
BOOT
Figure 4a. Non-Bootstrapped Typical Operating Circuit
Figures 3a–3f. MAX863 Switching Waveforms During Transition into Continuous Conduction
A
B
C
A
B
C
V OUT1 = 3.3V
PLOTS a-d: INTERNAL FEEDBACK
PLOTS e-f: UNCOMPENSATED,
EXTERNAL FEEDBACK
A: MOSFET DRAIN, 2V/div
B: V
OUT 1, 100mV/div, 3.3V DC OFFSET
C: INDUCTOR CURRENT, 1A/div
20 µs/div
a) I OUT1 = 287mA
20 µs/div
b) I OUT1 = 608mA
20 µs/div
c) I OUT1 = 767mA
OV
3.3V
0A
OV
3.3V
0A
20 µs/div
d) I OUT1 = 1.01A
20 µs/div
e) I OUT1 = 757mA
20 µs/div
f) I OUT1 = 881mA