MAX8645Y Maxim Integrated Products, MAX8645Y Datasheet - Page 12

• Manufacturer Part Number: MAX8645Y
• Description: (MAX8645X/Y) 1x/1.5x/2x White LED Charge Pumps
• Manufacturer: Maxim Integrated Products

1x/1.5x/2x White LED Charge Pumps with Two
LDOs in 4mm x 4mm TQFN
Figure 4. Schematic for When Fewer than 8 LEDs Are Acceptable
For LED drivers, input ripple is more important than out-
put ripple. Input ripple is highly dependent on the
source supply’s impedance. Adding a lowpass filter to
the input further reduces input ripple. Alternately,
increasing C
a small increase in footprint. The 1x mode always has
very low input ripple.
Typical operating waveforms shown in the Typical
Operating Characteristics show input ripple current in
1x, 1.5x, and 2x modes.
As shown in Table 2, the LDO output voltages, LDO1
and LDO2 are pin programmable by the logic states of
P1 and P2. P1 and P2 are tri-level inputs: IN, open, and
GND. The input voltage, V
selected LDO1 and LDO2 voltages. The logic states of
P1 and P2 can be programmed only during ENLDO
low. Once the LDO_ voltages are programmed, their
values do not change by changing P1 or P2 during
ENLDO high.
Use only ceramic capacitors with an X5R, X7R, or better
dielectric. See Table 3 for a list of recommended parts.
12
LDO Output Voltage Selection (P1 and P2)
______________________________________________________________________________________
IN
to 22µF cuts input ripple in half with only
INPUT
2.7V TO 5.5V
ON/OFF AND
SELECTION
IN
VOLTAGE
Component Selection
10μF
, must be greater than the
6.81kΩ
Input Ripple
PIN
IN
GND
ENM2
ENM1
ENF
ENLDO
P1
P2
SETM
C1P
4.12kΩ
1μF
C1N
SETF
MAX8645X
MAX8645Y
REFBP
C2P
0.01μF
1μF
C2N
LDO1
LDO2
PGND
OUT
Connect a 1µF ceramic capacitor between LDO1 and
GND, and a second 1µF ceramic capacitor between
LDO2 and GND for 200mA applications. The LDO out-
put capacitor’s (C
(ESR) affects stability and output noise. Use output
capacitors with an ESR of 0.1Ω or less to ensure stability
and optimum transient response. Connect C
close as possible to the MAX8645X/MAX8645Y to mini-
mize the impact of PCB trace inductance.
Table 2. P1 and P2, LDO Output Voltage
Selection
M1
M2
M3
M4
M5
M6
F1
F2
OPEN
OPEN
OPEN
GND
GND
GND
P1
IN
IN
IN
1μF
10μF
OPEN
OPEN
OPEN
GND
GND
GND
UP TO 240mA
P2
IN
IN
IN
OUTPUT
1μF
MAIN
LDO1 (V) LDO2 (V) LDO1 (V) LDO2 (V)
3.3
3.0
2.8
3.3
2.6
2.6
3.0
2.8
2.5
LDO
FLASH
MAX8645X
) equivalent series resistance
1.8
1.5
1.5
1.5
1.8
1.5
1.8
1.8
1.8
2.8
2.8
2.9
2.6
2.6
2.8
2.9
2.9
2.9
MAX8645Y
LDO_
2.6
2.8
1.5
1.9
2.6
1.9
1.8
1.9
2.9
as