Datasheet MAX1573 (Analog Devices) - 7

White LED 1x/1.5x Charge Pump in UCSP and Thin QFN MAX1573 PC Board Layout and Routing
3.4V, if only two or three LEDs are used, or if four LEDs The MAX1573 is a high-frequency switched-capacitor are used at 10mA or less. Some typical external com- voltage regulator. For best circuit performance, use a ponent values are shown in Table 2. solid ground plane and place CIN and COUT as close Under normal operating conditions, power dissipation to the MAX1573 as possible. Also, place their ground is low. Maximum power dissipation occurs at an input pads close together and as close as possible to GND. voltage of 4.2V and all four LEDs (with VF = 4V) are dri- See the MAX1573 EV kit for an example. ven with 30mA per LED. The power is calculated as:
Component Selection
PD = [(1.5 x VIN) - VF] x 120mA = 276mW Use ceramic capacitors with an X5R dielectric or better At higher input voltages, the MAX1573 switches to 1x temperature coefficient. The transfer capacitors may be mode and power dissipation decreases. reduced in value if the input voltage does not fall below
Pin Configurations (continued)
1μF 1μF TOP VIEW 1 2 3 4 C1P C1N C2P C2N V 1Ω IN IN OUT C1P OUT EN1 EN2 1μF A 2.2μF 2.2μF C2N C2P SET MAX1573 B EN1 LED1 EN2 LED2 IN LED4 LED2 SET LED3 C LED4 C1N GND LED3 LED1 RSET D GND
UCSP 4
✕
4
Figure 3. C-R-C Filter Reduces Input Ripple
Table 2. Typical Component Values COMPONENT VALUE (µF) MANUFACTURER PART DESCRIPTION
Input/Output 1 Taiyo Yuden JMK107BJ105KA 1µF ±10%, 6.3V X5R ceramic capacitor (0603) Capacitors 1 Taiyo Yuden JMK107BJ105KA 1µF ±10%, 6.3V X5R ceramic capacitor (0603) Transfer 0.47 Taiyo Yuden LMK107BJ474KA 0.47µF ±10%, 10V X5R ceramic capacitor (0603) Capacitors 0.22 Taiyo Yuden LMK107BJ224KA 0.22µF ±10%, 10V X7R ceramic capacitor (0603) LED — Nichia NSCW215T White LEDs RSET As required Panasonic — ±1% resistor (0603)
Chip Information
TRANSISTOR COUNT: 3655 PROCESS: BiCMOS
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