View MAX1579EVKIT_990074.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-3610; Rev 0; 3/05
MAX1579 Evaluation Kit
General Description
The MAX1579 evaluation kit (EV kit) is a fully assembled and tested circuit for evaluating the MAX1578/ MAX1579. This MAX1579 EV kit drives six white LEDs in series for backlighting and includes complete bias supplies for small TFT displays. The internal charge pumps for the TFT bias supplies provide fixed +15V at 100A for VON, -10V at 100A for VOFF, and +5V at 25mA for the source driver. The MAX1579 EV kit can also evaluate the MAX1578. To evaluate the MAX1578, order a free sample along with this EV kit.
Features
o LCD Bias Outputs (+5V/25mA, +15V/100A, -10V/100A) Output Sequencing No External Diodes Required POS, NEG, and MAIN Are Autodischarged During Shutdown o LED Backlight Step-Up DC-DC Converter Series Connection for Uniform Illumination Supports Up to 8 LEDs at 25mA (max) 900mW (max) Power Overvoltage Protection Low Input/Output Ripple Soft-Start Fast 1MHz PWM Operation for Small Component Size Temperature Derating Function (MAX1579) o High Efficiency Bias: 83% (5.0V at 25mA, 15V/-10V at 100A) LED: 84% (6 LEDs at 20mA) o Independent Enable Inputs for LED and Bias Power o Thermal-Shutdown Protection o 1A Shutdown Current o Tiny 4mm x 4mm Thin QFN Package o Fully Assembled and Tested
Evaluates: MAX1578/MAX1579
Component List
DESIGNATION QTY C1, C6 2 DESCRIPTION 4.7F, 6.3V X5R ceramic capacitors (0603) Murata GRM188R60J475KE19 0.1F, 50V X7R ceramic capacitor (0603) TDK C1608X7R1H104K 0.1F, 10V X7R ceramic capacitor (0402) TDK C1005X7R1A104K 2.2F, 6.3V X5R ceramic capacitors (0603) Taiyo Yuden JMK107BJ225KA 1F, 6.3V X5R ceramic capacitors (0402) Murata GRM155R60J105KE19 1F, 16V X7R, ceramic capacitors (0805) TDK C2012X7R1C105K Not installed CMOSH-4E, 40V, 200mA Central Semiconductor (SOD-523) Shorted LED footprint White LEDs Nichia NSCW215T 2-pin header 3-pin header 22H, 250mA inductor (1210) Murata LQH32CN220K53 22.1 1% resistor (0402) 100k 5% resistor (0402) 200 5% resistors (0402) Not installed, PC board short MAX1579ETG Shunt, 2 position MAX1579 EV kit PC board
C2
1
C3
1
C4, C5 C7, C8, C9, C12, C13 C10, C11, C14 C15 D1 D2, D3 D4-D9 JU1 JU2 L1 R1 R2 R3, R4 R5 U1 None None
2
5
3 0 1 0 6 1 1 1 1 1 2 0 1 2 1
Ordering Information
PART MAX1579EVKIT TEMP RANGE 0C to +70C IC PACKAGE 24 Thin QFN 4mm x 4mm
Quick Start
Recommended Equipment
* * A 2.7V to 5.5V power supply or battery capable of delivering 1A Three voltmeters (DMMs)
Procedure
The MAX1579 EV kit is fully assembled and tested. Follow the steps below to verify board operation: 1) Verify that the shunt on JU2 is connected to ON (1 and 2). Verify that a shunt is on JU1. 2) Preset the power supply to between 2.7V and 5.5V. Turn off the power supply. Do not turn on the power supply until all connections are completed.
1
________________________________________________________________ Maxim Integrated Products
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.
MAX1579 Evaluation Kit Evaluates: MAX1578/MAX1579
Component Suppliers
SUPPLIER Central Semiconductor Murata Nichia Taiyo Yuden TDK Vishay PHONE 631-435-1110 814-237-1431 248-352-6575 408-573-4150 847-803-6100 402-563-6866 WEBSITE www.centralsemi.com www.murata.com www.nichia.com www.t-yuden.com www.component.tdk.com www.vishay.com
Charge-Pump Output Sequencing
The outputs of the MAX1578/MAX1579 charge pumps are sequenced to turn on and off in a predictable fashion. The MAX1578/MAX1579 data sheet describes charge-pump output sequencing in detail.
Backlight Shutdown Control
The shunt on JU1 can be used to enable or shut down the backlight LEDs. The EV kit default position has the shunt placed on JU1 for backlight LEDs enabled. Remove the shunt on JU1 to shut down the backlight LEDs. The pad CTRL can also be used to shut down the backlight LEDs with an external logic signal. Remove the shunt from JU1 before connecting a logic signal to CTRL, as JU1 and CTRL are connected together with a 100k resistor on the PC board.
Note: Indicate that you are using the MAX1579 when contacting these component suppliers.
3) Connect the positive power-supply terminal to the pad labeled IN on the EV kit. 4) Connect the power-supply ground terminal to the pad labeled GND on the EV kit. 5) Connect the positive terminal of a voltmeter (V1) to the pad labeled MAIN on the EV kit. Connect the ground terminal of the voltmeter to the pad labeled GND on the EV kit. 6) Connect the positive terminal of a voltmeter (V2) to the pad labeled POS on the EV kit. Connect the ground terminal of the voltmeter to the pad labeled GND on the EV kit. 7) Connect the positive terminal of a voltmeter (V3) to the pad labeled NEG on the EV kit. Connect the ground terminal of the voltmeter to the pad labeled GND on the EV kit. 8) Turn on the power supply and verify that the backlight LEDs (D4-D9) are lit. 9) The V1 voltmeter should read near +5V. 10) The V2 voltmeter should read near +15V. 11) The V3 voltmeter should read near -10V.
Ambient Temperature Derating Function (MAX1579)
The MAX1579 limits the maximum LED current depending on its die temperature. VCS is limited to 340mV up to +42C. Once the temperature reaches +42C, the maximum VCS declines by 6mV/C until the minimum of 40mV is reached at high temperature.
Adjusting LED Current
Set the maximum LED current by adjusting the value of R1, which is connected from CS to GND. Calculate the resistance as follows: R1 = 327mV for MAX1578 ILED 340mV for MAX1579 ILED
R1 =
where ILED is the desired maximum current through the LEDs in amps when VCTRL is 1.65V or greater.
LED Dimming Control
Using a DAC VCTRL controls the LED drive current. The voltage at CS regulates to 20% of V CTRL to control the current through the LEDs and, therefore, the brightness. Drive CTRL using a DAC with an output voltage between 0.24V and 1.65V to control the brightness of the LEDs. Increasing VCTRL beyond 1.65V results in no further brightness increase. Hold V CTRL below 100mV for longer than 10.5ms to shut down the boost converter.
Detailed Description
Bias-Supply Shutdown Control
The shunt on JU2 can be used to enable or shut down the bias supply. The EV kit default position has the shunt placed on pins 1 and 2 to enable the bias supply. Place the shunt on pins 2 and 3 to shut down the bias supply. The pad ONBIAS can also be used to shut down the bias supply with an external logic signal. Remove the shunt from JU2 before connecting a logic signal to ONBIAS, as pin 2 of JU2 and ONBIAS are connected together on the PC board.
2
_______________________________________________________________________________________
MAX1579 Evaluation Kit Evaluates: MAX1578/MAX1579
L1 22H IN 2 1 JU1 R2 100k CTRL C3 0.1F R5 SHORTED 15 CTRL PGND 13 COMP 18 C1 4.7F 21 IN 17 LX OUT 16 C2 0.1F D2 SHORTED D3 SHORTED D4 D5 D6 D7 CS 14 R1 22.1 JU2 C4 2.2F GND 11 ONBIAS D8 D9 CS C15 OPEN
D1 OUT
IN 1 2 3
ONBIAS
U1
23 19 C5 2.2F
MAX1579
C1P C1N MAIN VDD
24
C6 4.7F
1 C7 1F
MAIN
22 20 6
C2P GND C2N PMP CU3
12
R3 200 C8 1F
C12 1F
4
C10 1F
2 8 R4 200 C9 1F 3 9
CU1 CD1
NEG 7 PMPB
10 C14 1F
NEG
C13 1F
CU2 CD2
POS
5 C11 1F
POS
Figure 1. MAX1579 EV Kit Schematic
Using Direct PWM into CTRL Another useful technique for LED dimming control is the application of a logic-level PWM signal applied directly to CTRL. LED current may be varied from zero to maximum. The frequency range of the PWM signal is from 200Hz to 200kHz, while 0% duty cycle corre-
sponds to zero current and 100% duty cycle corresponds to maximum current. The error amplifier and compensation capacitor form a lowpass filter so PWM dimming results in DC current to the LEDs without the need for any additional RC filters.
_______________________________________________________________________________________
3
MAX1579 Evaluation Kit Evaluates: MAX1578/MAX1579
Figure 2. MAX1579 EV Kit Component Placement Guide-- Component Side
Figure 3. MAX1579 EV Kit PC Board Layout--Component Side
Figure 4. MAX1579 EV Kit PC Board Layout--Solder Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
4 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.

▲Up To Search▲

Price & Availability of MAX1579EVKIT

	To Download MAX1579EVKIT Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .