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General Description

The MAX16801A/B/MAX16802A/B high-brightness (HB)

LED driver-control ICs contain all the circuitry required

for the design of wide-input-voltage-range LED drivers

for general lighting and display applications. The

MAX16801 is well suited for universal input (rectified

85VAC to 265VAC) LED drivers, while the MAX16802 is

intended for low-input-voltage (10.8VDC to 24VDC) LED

drivers.

When the LED current needs to be tightly regulated, an

additional on-board error amplifier with 1% accurate ref-

erence can be utilized. A wide dimming range can be

implemented by using low-frequency PWM dimming.

The MAX16801/MAX16802 feature an input undervoltage

lockout (UVLO) for programming the input-supply start

voltage, and to ensure proper operation during brownout

conditions. The MAX16801 has an internal-bootstrap

undervoltage lockout circuit with a large hysteresis that

simplifies offline LED driver designs. The MAX16802 does

not have this internal bootstrap circuit and can be biased

directly from a +12V rail.

The 262kHz fixed switching frequency is internally

trimmed, allowing for optimization of the magnetic and fil-

ter components, resulting in a compact, cost-effective

LED driver. The MAX16801A/MAX16802A are offered with

50% maximum duty cycle. The MAX16801B/MAX16802B

are offered with 75% maximum duty cycle. These devices

are available in an 8-pin µMAX

package and operate

over the -40°C to +85°C temperature range.

Applications

Features

♦ Suitable for Buck, Boost, Flyback, SEPIC, and

Other Topologies

♦ Up to 50W or Higher Output Power

♦ Universal Offline Input Voltage Range: Rectified

85VAC to 265VAC (MAX16801)

♦ IN Pin Directly Driven From 10.8VDC to 24VDC

Input (MAX16802)

♦ Internal Error Amplifier with 1% Accurate

Reference for Precise LED Current Regulation

♦ PWM or Linear Dimming

♦ Fixed Switching Frequency of 262kHz ±12%

♦ Thermal Shutdown

♦ Digital Soft-Start

♦ Programmable Input Startup Voltage

♦ Internal Bootstrap UVLO with Large Hysteresis

(MAX16801)

♦ 45µA (typ) Startup Supply Current, 1.4mA (typ)

Operating Supply Current

♦ 50% (MAX16801A/MAX16802A) or 75%

(MAX16801B/MAX16802B) Maximum Duty Cycle

♦ Available in a Tiny 8-Pin µMAX Package

MAX16801A/B/MAX16802A/B

Offline and DC-DC PWM Controllers for

High-Brightness LED Drivers

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3880; Rev 2; 1/10

PART

TEMP

RANGE

PIN-

PACKAGE

MAX16801AEUA+ -40°C to +85°C 8 µMAX

MAX16801BEUA+ -40°C to +85°C 8 µMAX

MAX16802AEUA+ -40°C to +85°C 8 µMAX

MAX16802BEUA+ -40°C to +85°C 8 µMAX

+Denotes lead-free package.

Offline and DC-DC LED

Drivers

RGB Back Light for LCD

TVs and Monitors

Commercial and

Industrial Lighting

Decorative and

Architectural Lighting

EVALUATION KIT

AVAILABLE

MAX16802B

10.8VDC TO 24VDC

PWM

GND

C1 R1

LEDs

COMP

DIM/FB

UVLO/EN IN

NDRV

GND

ENABLE

Typical Operating Circuit

Warning: The MAX16801/MAX16802 are designed to work with high voltages. Exercise caution.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

Summary of content (16 pages)

PAGE 1
9-3880; Rev 2; 1/10 KIT ATION EVALU E L B A AVAIL Offline and DC-DC PWM Controllers for High-Brightness LED Drivers Features ♦ Suitable for Buck, Boost, Flyback, SEPIC, and Other Topologies ♦ Up to 50W or Higher Output Power ♦ Universal Offline Input Voltage Range: Rectified 85VAC to 265VAC (MAX16801) ♦ IN Pin Directly Driven From 10.
PAGE 2
MAX16801A/B/MAX16802A/B Offline and DC-DC PWM Controllers for High-Brightness LED Drivers ABSOLUTE MAXIMUM RATINGS IN to GND..........................................................................-0.3V to +30V VCC to GND ......................................................................-0.3V to +13V DIM/FB, COMP, UVLO, CS to GND..........................-0.3V to +6V NDRV to GND.............................................-0.3V to (VCC + 0.
PAGE 3
Offline and DC-DC PWM Controllers for High-Brightness LED Drivers (VIN = +12V (MAX16801: VIN must first be brought up to +23.6V for startup), 10nF bypass capacitors at IN and VCC, CNDRV = 0µF, VUVLO = +1.4V, VDIM/FB = +1.0V, COMP = unconnected, VCS = 0V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 4
Typical Operating Characteristics (VUVLO/EN = +1.4V, VFB = +1V, COMP = unconnected, VCS = 0V, TA = +25°C, unless otherwise noted.) 21.55 10.1 MAX16801 VIN FALLING UVLO/EN WAKE-UP THRESHOLD vs. TEMPERATURE 1.280 UVLO/EN RISING 1.275 MAX16801 toc03 MAX16801 VIN RISING MAX16801 toc01 21.60 BOOTSTRAP UVLO SHUTDOWN LEVEL vs. TEMPERATURE MAX16801 toc02 BOOTSTRAP UVLO WAKE-UP LEVEL vs. TEMPERATURE 10.0 21.45 UVLO/EN (V) VIN (V) VIN (V) 21.50 9.9 21.40 1.270 1.265 1.260 9.8 21.35 1.255 9.
PAGE 5
Offline and DC-DC PWM Controllers for High-Brightness LED Drivers SWITCHING FREQUENCY vs. TEMPERATURE 15 10 5 255 250 -3σ 270 280 290 300 310 10 -20 0 20 40 60 80 230 240 250 260 270 280 SWITCHING FREQUENCY (kHz) PROPAGATION DELAY FROM CURRENT-SENSE COMPARATOR INPUT TO NDRV vs. TEMPERATURE UVLO/EN PROPAGATION DELAY vs. TEMPERATURE REFERENCE VOLTAGE vs. TEMPERATURE 60 55 50 -20 0 20 40 60 80 VIN = 12V 1.229 1.228 1.227 1.226 UVLO/EN FALLING 1.
PAGE 6
Typical Operating Characteristics (continued) (VUVLO/EN = +1.4V, VFB = +1V, COMP = unconnected, VCS = 0V, TA = +25°C, unless otherwise noted.) ERROR-AMPLIFIER OPEN-LOOP GAIN AND PHASE vs. FREQUENCY NDRV OUTPUT IMPEDANCE vs. TEMPERATURE 4.8 4.6 100 30 80 10 GAIN 60 4.4 GAIN (dB) 4.2 4.0 3.8 50 -10 40 -30 20 -50 0 -70 PHASE -20 -90 3.6 -40 -110 3.4 -60 -130 3.2 -80 -150 3.0 -100 -40 -20 0 20 40 60 0.
PAGE 7
Offline and DC-DC PWM Controllers for High-Brightness LED Drivers the power dissipation across R1, even at the high end of the universal AC input voltage. An internal shutdown circuit protects the device whenever the junction temperature exceeds +130°C (typ). Dimming Linear dimming can be implemented by creating a summing node at CS, as shown in Figures 6 and 7. Low-frequency PWM (chopped-current) dimming is possible by applying an inverted-logic PWM signal to the DIM/FB pin of the IC (Figure 8).
PAGE 8
MAX16801A/B/MAX16802A/B Offline and DC-DC PWM Controllers for High-Brightness LED Drivers VDC R VDC Q R IN IN MAX16802A D D MAX16802A C (b) (a) Figure 2. (a) Resistor-Zener and (b) Transistor-Zener-Resistor Bias Arrangements in applications with higher input DC voltages by implementing resistor-Zener bias (Figure 2a) or transistorZener-resistor bias (Figure 2b). MAX16801/MAX16802 Undervoltage Lockout The MAX16801/MAX16802 have an input voltage UVLO/EN pin. The threshold of this UVLO is +1.28V.
PAGE 9
Offline and DC-DC PWM Controllers for High-Brightness LED Drivers VCC 2V/div MAX16801 VIN PIN 5V/div 0 The MAX16801/MAX16802 soft-start feature allows the LED current to ramp up in a controlled manner. Softstart begins after UVLO deasserts. The voltage applied to the noninverting node of the amplifier ramps from 0 to +1.23V over a 60ms soft-start timeout period. Figure 4 shows a typical 0.5A output current during startup. Note the staircase increase of the LED current.
PAGE 10
MAX16801A/B/MAX16802A/B Offline and DC-DC PWM Controllers for High-Brightness LED Drivers Applications Information Assuming C1 > C2, calculate the value of R1 as follows: Startup Time Considerations for HighBrightness LED Drivers Using MAX16801 The IN bypass capacitor C1 supplies current immediately after wake-up (Figure 5). The size of C1 and the connection configuration of the tertiary winding determine the number of cycles available for startup.
PAGE 11
Offline and DC-DC PWM Controllers for High-Brightness LED Drivers Figure 8 shows an offline isolated flyback HB LED driver with low-frequency PWM using MAX16801. The PWM signal needs to be inverted (see the Functional Diagram). Transformer T1 provides full safety isolation and operation from universal AC line (85VAC to 265VAC). D1 T1 VSUPPLY D2 R1 R2 C4 Q1 NDRV IN VOUT LEDs C1 VCC CS R4 C2 COMP R6 R7 MAX16801 C3 GND DIM/FB UVLO/EN R3 R5 GND Figure 5.
PAGE 12
MAX16801A/B/MAX16802A/B Offline and DC-DC PWM Controllers for High-Brightness LED Drivers VIN 10.8V TO 24V R1 UVLO/EN DIM/FB 1 8 2 7 COMP 3 CS MAX16802B 4 6 5 LED(s) L1 IN C4 VCC NDRV Q1 D1 GND R2 R4 R3 DIMMING C2 C3 R5 C1 GND Figure 6. MAX16802 Flyback HB LED Driver with Dimming Capability, 10.8V to 24V Input Voltage Range VIN 10.
PAGE 13
Offline and DC-DC PWM Controllers for High-Brightness LED Drivers MAX16801A/B/MAX16802A/B OPTIONAL ONLY WHEN PWM DIMMING IS USED D3 T1 D1 C4 D2 R2 R1 UNIVERSAL AC INPUT Q1 NDRV VCC LEDs C3 BRIDGE RECTIFIER IN C6 GND MAX16801B CS C1 C2 DIM/FB R4 UVLO/EN R3 *PWM C5 *WARNING: PWM DIMMING SIGNAL IS SHOWN AT THE PRIMARY SIDE. USE AN OPTOCOUPLER FOR SAFETY ISOLATION OF THE PWM SIGNAL. Figure 8.
PAGE 14
MAX16801A/B/MAX16802A/B Offline and DC-DC PWM Controllers for High-Brightness LED Drivers Functional Diagram IN IN CLAMP 26.1V VCC VCC IN REGULATOR BOOTSTRAP UVLO** REG_OK DIGITAL SOFT-START VL REFERENCE 1.23V 21.6V 9.74V UVLO (INTERNAL 5.25V SUPPLY) UVLO 1.28V 1.23V COMP FB DRIVER S ERROR AMP NDRV Q R CPWM VOPWM CS *OSCILLATOR 264kHz 1.38V THERMAL SHUTDOWN VCS 0.
PAGE 15
Offline and DC-DC PWM Controllers for High-Brightness LED Drivers PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 8 µMAX — 21-0036 ______________________________________________________________________________________ 15 MAX16801A/B/MAX16802A/B Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only.
PAGE 16
MAX16801A/B/MAX16802A/B Offline and DC-DC PWM Controllers for High-Brightness LED Drivers Revision History REVISION NUMBER REVISION DATE 0 10/05 Initial release 1 1/06 MAX16802AEUA+ parts are available 2 1/10 Corrected formulas, updated subscripts, and removed package outline DESCRIPTION PAGES CHANGED — 1 1, 2, 3, 6–14 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.