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MAX8630W

125mA 1x/1.5x Charge Pumps for 5 White LEDs in 3mm x 3mm TDFN

Maxim Integrated 

125mA 1x/1.5x Charge Pumps for 5 White LEDs

in 3mm x 3mm TDFN

Shutdown Mode

When both ENM and ENS (or PWM) are held low for

4ms or longer, the MAX8630_ is shut down and put in a

low-current mode. OUT is internally pulled to GND with

5kΩ during shutdown.

Overvoltage Protection

If any LED fails as an open circuit, the corresponding

VLED_ goes to 0V, and the output voltage is limited to

about 5V by gating on/off the charge pump. In case

any LED_ is floating or grounded, the MAX8630_ oper-

ates in the same overvoltage protection mode. To avoid

overvoltage protection mode when using fewer than

five LEDs, connect any unused LED_ to OUT. The

MAX8630_ contains special circuitry to detect this con-

dition and disables the corresponding current regulator

to avoid wasting battery current.

Thermal Shutdown

The MAX8630_ includes a thermal-protection circuit

that shuts down the IC when the die temperature reach-

es about +160°C. The part turns on after the IC cools

by approximately 20°C.

Temperature Derating Function

The MAX8630 contains a derating function that auto-

matically limits the LED current at high temperatures in

accordance with the recommended derating curve of

popular white LEDs. The derating function enables the

safe usage of higher LED currents at room tempera-

ture, thus reducing the number of LEDs required to

backlight the display. The derating circuit protects the

LEDs from overheating at high PCB temperatures. The

derating circuit limits the LED current by reducing the

internal 600mV reference voltage above +40°C at

approximately -1.67%/°C. The typical derating function

characteristic is shown in the Typical Operating

Characteristics.

Applications Information

Driving Fewer than 5 LEDs

To avoid overvoltage protection mode when using

fewer than five LEDs, connect any unused LED_ to

OUT. The MAX8630_ contains special circuitry to

detect this condition and disables the corresponding

current regulator to avoid wasting battery current.

Input Ripple

For LED drivers, input ripple is more important than out-

put ripple. Input ripple depends on the source supply’s

output impedance. Adding a lowpass filter to the input

of the MAX8630_ further reduces input ripple.

Alternatively, increasing CIN to 2.2µF (or 4.7µF) cuts

input ripple in half (or in fourth) with only a small

increase in footprint. The 1x mode always has very low

input ripple.

Component Selection

Ceramic capacitors are recommended due to their

small size, low cost, and low ESR. Select ceramic

capacitors that maintain their capacitance over temper-

ature and DC bias. Capacitors with X5R or X7R temper-

ature characteristics generally perform well. See Table

1 for a list of recommended components. Using a larg-

er value input capacitor helps to reduce input ripple

(see the Input Ripple section).

PCB Layout and Routing

The MAX8630_ is a high-frequency, switched-capacitor

voltage regulator. For best circuit performance, use a

solid ground plane and place CIN, COUT, C1, and C2

as close to the MAX8630_ as possible. See the

MAX8630_ evaluation kit for an example layout.

Chip Information

PROCESS: BiCMOS

Table 1. Recommended Components

DESIGNATION

VALUE MANUFACTURER

CIN, COUT, C1, C2

1µF

D1–D5

—

Taiyo Yuden

TDK

Nichia

PART NUMBER

JMK105 BJ105MV

C1005X5R0J105M

NSCW215T

DESCRIPTION

1µF ±20%, 6.3V X5R ceramic capacitors (0402)

1µF ±20%, 6.3V X5R ceramic capacitors (0402)

White LEDs

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