MAX1880EUG Maxim Integrated Products, MAX1880EUG Datasheet - Page 21

• Manufacturer Part Number: MAX1880EUG
• Description: DC/DC Switching Converters
• Manufacturer: Maxim Integrated Products

Specifications of MAX1880EUG

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The switching waveforms will appear noisy and asyn-
chronous when light loading causes pulse-skipping
operation; this is a normal operating condition that
improves light-load efficiency.
Figure 3. Discontinuous-to-Continuous Conduction Crossover
Point
Figure 4. Low-Power Charge Pump Block Diagram
2.7V TO 13V
V
V
SUPP
V
SUPD
POS
t
ON
V
V
POS
REF
= 1.25V
= 1 +
( )
______________________________________________________________________________________
C
R3
R4
OUT(POS)
V
t
OFF
REF
D2
D3
R3
R4
C
X(POS)
TIME
FBP
SUPP
DRVP
1.25V
V
REF
GND
Quad-Output TFT LCD DC-DC
I
I
PEAK
LOAD
MAX1778
MAX1880
MAX1881
MAX1882
OSC
The MAX1778/MAX1880/MAX1881/MAX1882 con-
trollers contain two independent low-power charge
pumps (Figure 4). One charge pump inverts the input
voltage and provides a regulated negative output volt-
age. The second charge pump doubles the input volt-
age and provides a regulated positive output voltage.
The controllers contain internal P-channel and N-chan-
nel MOSFETs to control the power transfer. The
internal MOSFETs switch at a constant frequency
(fCHP = fOSC/2).
During the first half-cycle, the N-channel MOSFET turns
on and charges flying capacitor C
This initial charge is controlled by the variable N-chan-
nel on-resistance. During the second half-cycle, the N-
channel MOSFET turns off and the P-channel MOSFET
turns on, level shifting C
connects C
tor C
diode drop (V
shifted flying capacitor voltage (V
charge flows from C
(D3) turns off.
Converters with Buffer
Dual Charge-Pump Regulator (MAX1778/
OUT(POS)
MAX1880/MAX1881/MAX1882 Only)
X(POS)
PGND
. If the voltage across C
POS
SUPN
DRVN
in parallel with the reservoir capaci-
+ V
REF
FBN
X(POS)
DIODE
C
X(NEG)
X(POS)
to C
R6
) is smaller than the level-
C
0.22μF
D4
D5
REF
OUT(POS)
Positive Charge Pump
R5
by V
CX(POS)
X(POS)
V
V
NEG
REF
SUPP
OUT(POS)
= 1.25V
= -
C
until the diode
OUT(NEG)
( )
R5
R6
(Figure 4).
V
2.7V TO 13V
volts. This
SUPN
+ V
V
V
REF
NEG
SUPP
plus a
21
),