PC Board Layout and Routing
The MAX1573 is a high-frequency switched-capacitor
voltage regulator. For best circuit performance, use a
solid ground plane and place C
IN
and C
OUT
as close
to the MAX1573 as possible. Also, place their ground
pads close together and as close as possible to GND.
See the MAX1573 EV kit for an example.
Component Selection
Use ceramic capacitors with an X5R dielectric or better
temperature coefficient. The transfer capacitors may be
reduced in value if the input voltage does not fall below
3.4V, if only two or three LEDs are used, or if four LEDs
are used at 10mA or less. Some typical external com-
ponent values are shown in Table 2.
Under normal operating conditions, power dissipation
is low. Maximum power dissipation occurs at an input
voltage of 4.2V and all four LEDs (with V
F
= 4V) are dri-
ven with 30mA per LED. The power is calculated as:
P
D
= [(1.5 x V
IN
) - V
F
] x 120mA = 276mW
At higher input voltages, the MAX1573 switches to 1x
mode and power dissipation decreases.
MAX1573
White LED 1x/1.5x Charge Pump in
UCSP and Thin QFN
_______________________________________________________________________________________ 7
PART DESCRIPTION
Input/Output
Capacitors
1 Taiyo Yuden JMK107BJ105KA 1µF ±10%, 6.3V X5R ceramic capacitor (0603)
1 Taiyo Yuden JMK107BJ105KA 1µF ±10%, 6.3V X5R ceramic capacitor (0603)
0.47 Taiyo Yuden LMK107BJ474KA
