Rainbow Electronics MAX8596Z User Manual

General Description

The MAX8595Z/MAX8596Z drive up to 8 white LEDs
with constant current and high efficiency to provide
LCD backlighting in cell phones, PDAs, and other
handheld devices. The series connection allows the
LED currents to be identical for uniform brightness and
minimizes the number of traces to the LEDs. The
MAX8595Z regulates constant LED current over the
entire temperature range. The MAX8596Z features an
ambient-temperature derating function to avoid over­driving the white LEDs during high ambient tempera­tures, enabling higher drive current below +42°C.

A single Dual Mode™ input provides a simple means of
brightness adjustment and on/off control. Fast 1MHz
current-mode PWM operation allows for small input and
output capacitors and a small inductor while minimizing
ripple on the input supply/battery. Soft-start eliminates
inrush current during startup.

The MAX8595Z/MAX8596Z are available in a space­saving, 8-pin 3mm x 3mm TDFN package.

Applications

Cell Phones and Smart Phones
PDAs, Palmtops, and Wireless Handhelds
e-Books and Subnotebooks
White LED Display Backlighting

Features

♦ Up to 8 LEDs at 25mA
♦ Temperature Derating Function to Allow Fewer

LEDs for Same Light (MAX8596Z)

♦ 86% Efficiency (P

LEDs

/ PIN)

♦ 1.7% Current-Regulation Accuracy
♦ Output Overvoltage Protection
♦ Flexible Dimming Control

Analog
Direct-PWM Internal Filter

♦ 1MHz PWM Switching Frequency
♦ 0.1µF Output Capacitor
♦ 12mV

P-P

Low Input Ripple

♦ Soft-Start Eliminates Inrush Current
♦ 2.6V to 5.5V Input Range
♦ 0.3µA Shutdown Current
♦ Pin Compatible with the MAX1561 and MAX1599
♦ TDFN 3mm x 3mm x 0.8mm Package with

Exposed Paddle

MAX8595Z/MAX8596Z

High-Efficiency, 32V Step-Up Converters

with TADerating Option for 2 to 8 White LEDs

________________________________________________________________ Maxim Integrated Products 1

GND

COMP

CS

1

2

LX

PGND

IN

CTRL

OUT

TOP VIEW

3

4

MAX8595Z
MAX8596Z

8

76

5

TDFN

3mm x 3mm x 0.8mm

Pin Configuration

Ordering Information

MAX8595Z
MAX8596Z

IN LX

OUT

PGND

CS

CTRL

COMP

GND

0.1µF

2 TO 8 LEDs

200Hz TO 200kHz

ANALOG OR

PWM DIMMING

2.2µF

INPUT

2.6V TO 5.5V

OUTPUT

UP TO 34V

Typical Operating Circuit

19-3558; Rev 0; 8/04

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

PART

TEMP

RANGE

PIN-PACKAGE

PKG

CODE

MAX8595ZETA

T833-1

MAX8596ZETA

T833-1

Dual Mode is a trademark of Maxim Integrated Products, Inc.

-40°C to +85°C

-40°C to +85°C

8 TDFN 3mm x 3mm
8 TDFN 3mm x 3mm

MAX8595Z/MAX8596Z

High-Efficiency, 32V Step-Up Converters
with T

A

Derating Option for 2 to 8 White LEDs

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

IN to GND.................................................................-0.3V to +6V

PGND to GND .......................................................-0.3V to +0.3V

LX, OUT to GND.....................................................-0.3V to +37V

CTRL to GND...................-0.3V to the lower of +6V or (V

IN

+ 2V)

COMP, CS to GND ......................................-0.3V to (V

IN

+ 0.3V)

I

LX

...................................................................................1.0A

RMS

Continuous Power Dissipation (TA= +70°C)
8-Pin TDFN 3mm x 3mm

(derate 24.4mW/°C above +70°C)............................ 1950mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range.............................-65°C to +150°C

Lead Temperature (soldering, 10s).................................+300°C

ELECTRICAL CHARACTERISTICS

(VIN= 3.0V, L = 22µH, CIN= 2.2µF, C

OUT

= 0.1µF, C

COMP

= 0.1µF, R

SENSE

= 13Ω, V

CTRL

= 1.5V, TA= -40°C to +85°C, unless other-

wise noted. Typical values are at T

A

= +25°C.) (Note 1)

PARAMETER CONDITIONS

UNITS

Supply Voltage 2.6 5.5 V
UVLO Threshold V

IN

rising or falling

V
UVLO Hysteresis 30 mV
Quiescent Current No switching 0.5 0.7 mA

TA = +25°C 0.3 2

Shutdown Supply Current

CTRL = GND,
V

OUT

= V

IN T

A

= +85°C1

µA

OVLO Threshold V

OUT

rising 32 34 36 V

OVLO Hysteresis 2V

V

OUT

= 32V, V

CTRL

> 0.24V 9 20 35

TA = +25°C

1

OUT Input Bias Current

TA = +85°C 0.1

µA

Output Voltage Range (Note 2)

V

IN

-

V

D

32 V

ERROR AMPLIFIER

TA = +25°C
TA = 0°C to +85°C

CTRL to CS Regulation

V

CTRL

= 1.50V,

V

IN

= 2.6V to 5.5V

T

A

= -40°C to +85°C

V

TA = +25°C

1

CS Input Bias Current VCS = V

CTRL

/ 5

T

A

= +85°C

µA

MAX8595Z, V

CTRL

= 3.0V

347

TA = -40°C to +25°C

360

TA = +42°C

CS Maximum Brightness Clamp
Voltage

MAX8596Z,
V

CTRL

= 3.0V

T

A

= +85°C

mV

MAX8595Z

CTRL Voltage for CS Maximum
Brightness Clamp

MAX8596Z

V

CS Derating Function Start
Temperature

MAX8596Z, V

CTRL

= 3.0V

°C

MIN TYP MAX

2.10 2.38 2.55

OUT = IN, CTRL = GND

0.295 0.300 0.305

0.292 0.300 0.308

0.290 0.300 0.310

310 330
330 345

0.01

0.01

0.03

343

106.5

1.65

1.72
+42

MAX8595Z/MAX8596Z

High-Efficiency, 32V Step-Up Converters

with T

A

Derating Option for 2 to 8 White LEDs

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 3.0V, L = 22µH, CIN= 2.2µF, C

OUT

= 0.1µF, C

COMP

= 0.1µF, R

SENSE

= 13Ω, V

CTRL

= 1.5V, TA= -40°C to +85°C, unless other-

wise noted. Typical values are at T

A

= +25°C.) (Note 1)

PARAMETER CONDITIONS

MIN

TYP

MAX

UNITS

CS Derating Function Slope MAX8596Z, V

CTRL

= 3.0V, TA = +42°C to +85°C

mV/°C

CTRL Input Resistance V

CTRL

<

1.5V

780 kΩ

CTRL Dual-Mode Threshold

240 mV
CTRL Dual-Mode Hysteresis 5mV
CTRL Shutdown Enable Delay (Note 3) 6.0 8.2

ms

CS to COMP Transconductance

V

COMP

= 1.5V 32 50 82 µS

COMP Input Resistance to
Ground

In shutdown, UVLO or OVLO 20 kΩ

OSCILLATOR

Operating Frequency

1.0

MHz

PWM mode 12

Minimum Duty Cycle

Pulse skipping 0

%

Maximum Duty Cycle CTRL = IN, CS = GND 94 95 %

N-CHANNEL SWITCH

LX On-Resistance ILX = 190mA 0.8

Ω

TA = +25°C

5

LX Leakage Current

TA = +85°C1

µA

LX Current Limit Duty cycle = 90%

900 mA

Note 1: Parameters are 100% production tested at TA= +25°C. Limits over the operating temperature range are regulated by

design and characterization.

Note 2: V

D

is the forward-voltage drop of the Schottky diode in Figure 1.

Note 3: Time from CTRL going below the Dual-Mode threshold to IC shutdown.

VLX = 36V, CTRL = GND

-5.5
250 500
100 170

10.5

0.75

0.01

1.25

1.35

500 700