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PDF MAX17061 Data sheet ( Hoja de datos )
| Número de pieza | MAX17061 | |
| Descripción | 8-String White LED Driver | |
| Fabricantes | Maxim Integrated Products | |
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Hay una vista previa y un enlace de descarga de MAX17061 (archivo pdf) en la parte inferior de esta página. Total 26 Páginas | ||
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19-3211; Rev 0; 1/08
www.DataSheet4U.com
8-String White LED Driver with
SMBus for LCD Panel Applications
General Description
The MAX17061 is a high-efficiency driver for white light-
emitting diodes (LEDs). It is designed for large liquid-
crystal displays (LCDs) that employ an array of LEDs as
the light source. An internal switch current-mode step-up
controller drives the LED array, which can be configured
for up to eight strings in parallel and 10 LEDs per string.
Each string is terminated with ballast that achieves ±1.5%
current-regulation accuracy between strings, ensuring
even LED brightness. The MAX17061 has a wide input-
voltage range from 4.5V to 26V, and provides a fixed
25mA or adjustable 15mA to 30mA full-scale LED current.
The MAX17061 internally generates a DPWM signal for
accurate WLED dimming control. The DPWM frequency
is resistor programmable, while DPWM duty cycle is con-
trolled directly from an external PWM signal or through a
control word through the MAX17061’s SMBus™ inter-
face. This DPWM control provides a dimming range with
8-bit resolution and supports Intel display-power-saving
technology (DPST) to maximize battery life.
The MAX17061 has multiple features to protect the con-
troller from fault conditions. Separate feedback loops
limit the output voltage under any circumstance, ensur-
ing safe operation. Once an open string is detected,
the string is disabled while other strings operate nor-
mally. The MAX17061 also features short LED detec-
tion. The shorted strings are also disabled after a 2ms
fault blanking interval. The controller features cycle-by-
cycle current limit to provide stable operation and soft-
start capability. If the MAX17061 is in current-limit
condition, the step-up converter is latched off after an
internal timer expires. A thermal-shutdown circuit pro-
vides another level of protection.
The MAX17061’s step-up controller features an internal
150mΩ (typ), 45V (max) power MOSFET with local cur-
rent-sense amplifier for accurate cycle-by-cycle current
limit. This architecture greatly simplifies the external cir-
cuitry and saves PCB space. Low-feedback voltage at
each LED string 625mV (typ) at 25mA LED current helps
reduce power loss and improve efficiency. The
MAX17061 features selectable switching frequency
(500kHz, 750kHz, or 1MHz), which enables a wide vari-
ety of applications that can trade off component size for
operating frequency.
The MAX17061 is available in a thermally enhanced
28-pin, 4mm x 4mm Thin QFN package.
Applications
Notebook, Subnotebook,
and Tablet Computer
Displays
Automotive Systems
Handy Terminals
Features
o Accurate Dimming Control Using SMBus, PWM
Interface
o Dimming Range with 8-Bit Resolution
o Adjustable DPWM Frequency with 1.5% Accuracy
o Up to Eight Parallel Strings Multiple Series-
Connected LEDs
o ±1.5% Current Regulation Accuracy Between
Strings
o Low String Feedback Voltage: 625mV at 25mA
LED Current
o Full-Scale LED Current Adjustable from 15mA to
30mA, or Preset 25mA
o Open and Short LED Protections
o Output Overvoltage Protection
o 0.15Ω Internal HV Power MOSFET (45V max)
o Wide Input-Voltage Range from 4.5V to 26V
o 500kHz/750kHz/1MHz Selectable Switching
Frequency
o Small 28-Pin, 4mm x 4mm, Thin QFN package
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX17061ETI+ -40oC to +85oC 28 Thin QFN (4mm x 4mm)
+Denotes a lead-free package.
Simplified Operating Circuit
L1 D1
VIN
VOUT
VDD IN
VCC
ISET
LX1, 2
PGND1, 2
CCV OV
PWM
CLK
DATA
MAX17061
PWMI
PWMO
FB1
GND
N.C. OSC
FB2
FB3
FB4
SCL FB5
FB6
SDA FB7
FSET FB8
EP
R1
R2
Pin Configuration appears at end of data sheet.
SMBus is a trademark of Intel Corp.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
www.DataSheet4U.com
8-String White LED Driver with
SMBus for LCD Panel Applications
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 12V, CCCV = 0.022µF, RCCV = 5.1kΩ, VISET = VOSC = VDD = VCC, RFSET = 464kΩ, VPWMI = GND,
TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
BOOST CONVERTER
LX On-Resistance
LX Leakage Current
Operating Frequency
OSC High-Level Threshold
CONDITIONS
20mA from LX_ to PGND
45V on LX_
VOSC = VCC
VOSC = open
VOSC = GND
OSC Midlevel Threshold
OSC Low-Level Threshold
Maximum Duty Cycle
LX Current Limit
CONTROL INPUT
SDA, SCL Logic Input-High Level
SDA, SCL Logic Input-Low Level
PWMI Logic Input-High Level
PWMI Logic Input-Low Level
INPUT LEAKAGE
PWMI Leakage Current
ISET, FSET Leakage Current
OV Leakage Current
SDA, SCL Input Bias Current
SDA Output-Low Sink Current
OSC Leakage Current
LED CURRENT
Full-Scale FB_ Output Current
Duty cycle = 75%
ISET , FSET to VCC
VSDA = 0.4V
ISET = VCC
RISET = 133kΩ
RISET = 200kΩ
RISET = 266kΩ
ISET High-Level Threshold
ISET Output Voltage
Current Regulation Between Strings
Minimum FB_ Regulation Voltage
Maximum FB_ Ripple
FB_ On-Resistance
Full brightness
IFB_ = 25mA
IFB_ = 30mA
IFB_ = 20mA
IFB_ = 15mA
IFB_ = 20mA (COUT = 1µF, VOSC = VCC)
VFB_ = 50mV (includes 10Ω sense resistor)
MIN TYP MAX UNITS
0.89
675
450
VCC -
0.4
1.5
94
1.6
0.3
1
1.10
825
560
VCC -
2.0
0.4
97
Ω
µA
MHz
kHz
kHz
V
V
V
%
A
2.1 V
0.8 V
2.1 V
0.8 V
-0.3
+0.3
µA
+1 µA
-0.1
+0.1
µA
-1 +1 µA
4 mA
-3 +3 µA
24.5
28.6
19.0
14.3
VCC -
0.4
1.166
-1.5
425
575
380
285
25.5
31.4
21.0
15.7
1.306
+1.5
910
1100
740
560
200
28.4
mA
V
V
%
mV
mVP/P
Ω
_______________________________________________________________________________________ 5
5 Page 
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8-String White LED Driver with
SMBus for LCD Panel Applications
Pin Description (continued)
PIN NAME
FUNCTION
22 VDD Boost Regulator MOSFET Gate Drive Supply. Bypass VDD to GND with a ceramic capacitor of 1µF or greater.
5V Linear Regulator Output. VCC provides power to the MAX17061. Bypass VCC to GND with a ceramic
23 VCC capacitor of 1µF or greater. If VIN is less than or equal to 5.5V, tie VCC to IN to disable internal LDO and use
external 5V supply to VCC.
24
CCV
Step-Up Converter Compensation Pin. Connect a 0.022µF ceramic capacitor and 5.1kΩ resistor from CCV to
GND. When the MAX17061 shuts down, CCV is discharged to 0V through an internal 20kΩ resistor.
25 OV Overvoltage Sense. Connect OV to the center tap of a resistive voltage-divider from VOUT to ground. The
detection threshold for voltage limiting at OV is 1.236V (typ).
Full-Scale LED Current Adjustment Pin. The resistance from ISET to GND controls the full-scale current in
each LED string:
26 ISET
ILEDMAX = 20mA x 200kΩ/RISET
The acceptable resistance range is 133kΩ < RISET < 266kΩ, which corresponds to full-scale LED current of
30mA > ILEDMAX > 15mA. Connect ISET to VCC for a default full-scale LED current of 25mA.
27 FB1 LED String 1 Cathode Connection. FB1 is the open-drain output of an internal regulator, which controls
current through FB1. FB1 can sink up to 30mA. If unused, connect FB1 to VCC.
28 FB2 LED String 2 Cathode Connection. FB2 is the open-drain output of an internal regulator, which controls
current through FB2. FB2 can sink up to 30mA. If unused, connect FB2 to VCC.
—
EP
Exposed Backside Pad. Solder to the circuit board ground plane with sufficient copper connection to ensure
low thermal resistance. See the PCB Layout Guidelines section.
Detailed Description
The MAX17061 is a high-efficiency driver for arrays of
white LEDs. It contains a fixed-frequency current-
mode PWM step-up controller, a 5V linear regulator,
dimming control circuit, SMBus interface, internal
power MOSFET, and eight regulated current sources
(see Figure 2). When enabled, the step-up controller
boosts the output voltage to provide sufficient head-
room for the current sources to regulate their respec-
tive string currents. The MAX17061 features selectable
switching frequency (500kHz, 750kHz, or 1MHz), which
allows trade-offs between external component size and
operating efficiency. The control architecture automati-
cally skips pulses at light loads to improve efficiency
and prevents overcharging the output capacitor.
WLED brightness is controlled by turning the WLEDs
on and off with a DPWM signal. The DPWM frequency
can be accurately adjusted with a resistor. The bright-
ness of the LEDs is proportional to the duty cycle of the
DPWM signal, which is controlled externally through
either a PWM or 2-wire SMBus-compatible interface, or
both. When both interfaces are used at the same time,
the product of the PWM duty cycle and SMBus com-
mand value is used for the dimming control. This
DPWM control scheme provides a full dimming range
with 8-bit resolution.
The MAX17061 has multiple features to protect the con-
troller from fault conditions. Separate feedback loops limit
the output voltage in all circumstances. The MAX17061
checks each FB_ voltage during the operation. If one or
more strings are open, the corresponding FB_ voltages
are pulled below 175mV (typ), and open-circuit fault is
detected. As a result, the respective current sources are
disabled. When one or more LEDs are shorted and the
FB_ voltage exceeds 1.1 x VCC, short fault is detected
and the respective current source is disabled. In either
LED open or short conditions, the fault strings are dis-
abled while other strings can still operate normally. The
controller features cycle-by-cycle current limit to provide
stable operation and soft-start protection. In a current-
limit condition, the controller shuts down after a 128µs
overcurrent fault timer expires. A thermal-shutdown cir-
cuit provides another level of protection.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet MAX17061.PDF ] | |
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