MAX8631_08 Datasheet, PDF (13/15 Pages) Maxim Integrated Products – 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN

1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
1μF
1μF
INPUT
2.7V TO 5.5V
10μF
C1P C1N
PIN
IN
GND
C2P C2N
LDO1
LDO2
ON/OFF AND
VOLTAGE
SELECTION
OUT
MAX8631X
ENM2
MAX8631Y
ENM1
ENF
ENLDO
P1
P2
SETM SETF REFBP
M1
M2
M3
M4
F1
F2
F3
F4
PGND
6.81kΩ 4.12kΩ
0.01μF
1μF
1μF
OUTPUT
UP TO 240mA
10μF ^MAIN
FLASH
Figure 5. Schematic for When Fewer than 8 LEDs Is Acceptable
Typical operating waveforms shown in the Typical
Operating Characteristics show input ripple current in
1x, 1.5x, and 2x mode.
LDO Output Voltage Selection (P1 and P2)
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_IN, must be greater than the
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.
Component Selection
Use only ceramic capacitors with an X5R, X7R, or better
dielectric. See Table 3 for a list of recommended parts.
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_LDO) equivalent series resistance
(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_{LDO_} as
close to the MAX8631X/Y as possible to minimize the
impact of PC board trace inductance.
Table 2. P1 and P2, LDO Output Voltage
Selection
P1
IN
IN
IN
OPEN
P2
IN
OPEN
GND
IN
MAX8631X
LDO1 (V) LDO2 (V)
3.3
1.8
3.0
1.5
2.8
1.5
3.3
1.5
MAX8631Y
LDO1 (V) LDO2 (V)
2.8
2.6
2.8
2.8
2.9
1.5
2.6
1.9
OPEN OPEN 2.6
1.8
2.6
2.6
OPEN GND
2.6
1.5
2.8
1.9
GND IN
3.0
1.8
2.9
1.8
GND OPEN 2.8
1.8
2.9
1.9
GND GND
2.5
1.8
2.9
2.9
PC Board Layout and Routing
The MAX8631X/Y is a high-frequency switched-capaci-
tor voltage regulator. For best circuit performance, use
a solid ground plane and place C_IN, C_OUT, C3, and C4
as close to the MAX8631X/Y as possible. There should
be no vias on C_IN. Connect GND and PGND to the
exposed paddle directly under the IC. Refer to the
MAX8631X/Y evaluation kit for an example.
______________________________________________________________________________________ 13