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19-1666; Rev 1; 10/03

30V Internal Switch LCD Bias Supply

General Description

The MAX1605 boost converter contains a 0.5A internal

switch in a tiny 6-pin SOT23 package. The IC operates

from a +2.4V to +5.5V supply voltage, but can boost

battery voltages as low as 0.8V up to 30V at the output.

The MAX1605 uses a unique control scheme providing

the highest efficiency over a wide range of load condi-

tions. An internal 0.5A MOSFET reduces external com-

ponent count, and a high switching frequency (up to

500kHz) allows for tiny surface-mount components. The

current limit can be set to 500mA, 250mA, or 125mA,

allowing the user to reduce the output ripple and com-

ponent size in low-current applications.

Additional features include a low quiescent supply cur-

rent and a shutdown mode to save power. The

MAX1605 is ideal for small LCD panels with low current

requirements, but can also be used in other applica-

tions. A MAX1605EVKIT evaluation kit (EV kit) is avail-

able to help speed up design time.

Applications

LCD Bias Generators

Cellular/Cordless Phones

Palmtop Computers

Personal Digital Assistants (PDAs)

Organizers

Handy Terminals

Features

♦ Adjustable Output Voltage up to 30V

♦ 20mA at 20V from a Single Li+ Battery

♦ 88% Efficiency

♦ Up to 500kHz Switching Frequency

♦ Selectable Inductor Current Limit

(125mA, 250mA, or 500mA)

♦ 18µA Operating Supply Current

♦ 0.1µA Shutdown Current

♦ Available in Two Small Packages

6-Pin TDFN

6-Pin SOT23

= 0.8V TO V

OUT

= 2.4V TO 5.5V

OUT

= V

TO 30V

OFF

SHDN

LIM

GND

MAX1605

10µH

MAX1605

________________________________________________________________ Maxim Integrated Products 1

Pin Configuration

Typical Operating Circuit

LXGND

16FB

5 LIM

SHDN

MAX1605

SOT23

TOP VIEW

LIM

MAX1605

GND

SHDN

TDFN

3mm

Ordering Information

PART

TEMP

RANGE

PIN-

PACKAGE

SOT

MARK

MAX1605EUT-T

-40°C to +85°C

6 SOT23-6

AAHP

MAX1605ETT-T

-40°C to +85°C

6 TDFN

ABW

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.

Summary of content (12 pages)

PAGE 1
9-1666; Rev 1; 10/03 30V Internal Switch LCD Bias Supply The MAX1605 boost converter contains a 0.5A internal switch in a tiny 6-pin SOT23 package. The IC operates from a +2.4V to +5.5V supply voltage, but can boost battery voltages as low as 0.8V up to 30V at the output. The MAX1605 uses a unique control scheme providing the highest efficiency over a wide range of load conditions. An internal 0.
PAGE 2
MAX1605 30V Internal Switch LCD Bias Supply ABSOLUTE MAXIMUM RATINGS VCC, FB, LIM, SHDN to GND....................................-0.3V to +6V LX to GND ..............................................................-0.3V to +32V Continuous Power Dissipation (TA = +70°C) 6-Pin SOT23 (derate 8.7mW/°C above +70°C) ...........696mW 6-Pin TDFN (derate 24.4mW/°C above +70°C) .........1951mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ...............................
PAGE 3
0V Internal Switch LCD Bias Supply (VCC = SHDN = 3.3V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS CONTROL INPUTS VIH 2.4V ≤ VCC ≤ 5.5V SHDN Input Threshold VIL SHDN Input Bias Current ISHDN 0.8 × VCC 0.2 × VCC 2.4V ≤ VCC ≤ 5.5V VCC = 5.5V, V SHDN = 0 to 5.5V -1 LIM Input Low Level 2.4V ≤ VCC ≤ 5.5V LIM Input Float Level 2.4V ≤ VCC ≤ 5.5V, ILIM = ±0.5µA (VCC / 2) 0.2V LIM Input High Level 2.
PAGE 4
ELECTRICAL CHARACTERISTICS (continued) (VCC = SHDN = 3.3V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN MAX UNITS 0.4 V (VCC / 2) + 0.25V V LIM Input Low Level 2.4V ≤ VCC ≤ 5.5V LIM Input Float Level 2.4V ≤ VCC ≤ 5.5V, ILIM = ±0.5µA (VCC / 2) - 0.25V LIM Input High Level 2.4V ≤ VCC ≤ 5.5V VCC - 0.4V -2 LIM Input Bias Current SHDN = VCC, LIM = GND or VCC ILIM V 2 SHDN = GND µA 1 Note 1: All devices are 100% tested at TA = +25°C.
PAGE 5
30V Internal Switch LCD Bias Supply (VCC = 3.3V, VIN = 3.6V, L1 = 10µH, SHDN = LIM = VCC, VOUT(NOM) = 18V (Figure 3), TA = +25°C, unless otherwise noted.) EFFICIENCY vs. LOAD CURRENT (L1 = 100µH) 88 80 78 LIM = VCC (500mA) LIM = GND 5 10 15 20 100 0 25 5 10 15 20 25 LOAD CURRENT (mA) LOAD CURRENT (mA) CURRENT LIMIT vs. INPUT VOLTAGE SUPPLY CURRENT vs.
PAGE 6
30V Internal Switch LCD Bias Supply MAX1605 Pin Description PIN NAME FUNCTION 1 SHDN 2 VCC IC Supply Voltage (+2.4V to +5.5V). Bypass VCC to GND with a 0.1µF or greater capacitor. 3 GND Ground 4 LX Inductor Connection. The drain of an internal 30V N-channel MOSFET. LX is high impedance in shutdown. 5 LIM Inductor Current Limit Selection. Connect LIM to VCC for 500mA, leave LIM floating for 250mA, or connect LIM to GND for 125mA. 6 FB Feedback Input.
PAGE 7
30V Internal Switch LCD Bias Supply VCC (2.4V TO 5.5V) VCC VCC MAX1605 LIM VCC MAX1605 NO CONNECTION GND IPEAK = 500mA MAX1605 VCC (2.4V TO 5.5V) VCC (2.4V TO 5.5V) MAX1605 LIM LIM GND GND IPEAK = 250mA IPEAK = 125mA Figure 2. Setting the Peak Inductor Current Limit Setting the Output Voltage (FB) Separate/Same Power for L1 and VCC Adjust the output voltage by connecting a voltagedivider from the output (VOUT) to FB (Figure 3). Select R2 between 10kΩ to 200kΩ.
PAGE 8
MAX1605 30V Internal Switch LCD Bias Supply Design Procedure Inductor Selection Smaller inductance values typically offer smaller physical size for a given series resistance or saturation current. Circuits using larger inductance values may start up at lower input voltages and exhibit less ripple, but also provide reduced output power. This occurs when the inductance is sufficiently large to prevent the maximum current limit from being reached before the maximum on-time expires.
PAGE 9
30V Internal Switch LCD Bias Supply VCC = 2.4V TO 5.5V R3 1Ω C3 0.1µF D1* D2* C5 1µF MAX1605 L1 10µH VIN = 0.8V TO VOUT VNEG -19V C2 1µF D3** LX VCC C6 0.1µF R1 240kΩ MAX1605 LIM C1 1000pF C4 0.01µF FB R2 16.5kΩ ON OFF SHDN GND *D1, D2 = CENTRAL SEMICONDUCTOR CMPD7000 DUAL **D3 = CENTRAL SEMICONDUCTOR CMSD4448 (1N4148) Figure 4. Negative Voltage for LCD Bias saturation region.
PAGE 10
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 6LSOT.
PAGE 11
30V Internal Switch LCD Bias Supply 6, 8, &10L, DFN THIN.EPS D N PIN 1 INDEX AREA E E2 DETAIL A CL CL L A L e e PACKAGE OUTLINE, 6, 8, 10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY 21-0137 F 1 2 ______________________________________________________________________________________ 11 MAX1605 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications.
PAGE 12
MAX1605 30V Internal Switch LCD Bias Supply Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) COMMON DIMENSIONS SYMBOL A MIN. 0.70 0.80 D 2.90 3.10 E 2.90 3.10 A1 L 0.00 0.05 k MAX. 0.40 0.20 0.25 MIN. A2 0.20 REF. PACKAGE VARIATIONS PKG. CODE N D2 E2 e JEDEC SPEC b [(N/2)-1] x e T633-1 6 1.50±0.10 2.30±0.10 0.