MAXIM MAX16807

19-0655; Rev 2; 8/09
KIT
ATION
EVALU
E
L
B
AVAILA
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
Features
The MAX16807 is an integrated, high-efficiency white or
RGB LED driver. It is designed for LCD backlighting
and other LED lighting applications with multiple strings
of LEDs. The MAX16807 current-mode PWM controller
regulates the necessary voltage to the LED array.
Depending on the input voltage and LED voltage
range, it can be used with boost or buck-boost (SEPIC)
topologies. The MAX16807 features an 8V to 26.5V
input voltage range. A wide range of adjustable frequency (20kHz to 1MHz) allows design optimization for
efficiency and minimum board space.
The MAX16807 LED driver includes eight open-drain,
constant-current-sinking LED driver outputs rated for
36V continuous operation. The LED current-control circuitry achieves ±3% current matching among strings
and enables paralleling of outputs for LED string currents higher than 55mA. The output-enable pin is used
for simultaneous PWM dimming of all output channels.
Dimming frequency range is 50Hz to 30kHz and dimming ratio is up to 5000:1. The constant-current outputs
are single resistor programmable and the LED current
can be adjusted up to 55mA per output channel.
The MAX16807 operates either in stand-alone mode or
with a microcontroller (µC) using an industry-standard, 4wire serial interface.
o Eight Constant-Current Output Channels (Up to
55mA Each)
o ±3% Current Matching Among Outputs
o Paralleling Channels Allows Higher Current per
LED String
o Output Rated for 36V Continuous Voltage
o Output-Enable Pin for PWM Dimming (Up to 30kHz)
o One Resistor Sets LED Current for All Channels
o Wide Dimming Ratio Up to 5000:1
o Low Current-Sense Reference (300mV) for High
Efficiency
o 8V to 26.5V Input Voltage or Higher with External
Biasing Devices
o 4-Wire Serial Interface to Control Individual
Output Channels
The MAX16807 includes overtemperature protection,
operates over the full -40°C to +125°C temperature
range, and is available in a thermally enhanced, 28-pin
TSSOP exposed paddle package.
Ordering Information
Applications
LCD White or RGB LED Backlighting:
LCD TVs, Desktop, and Notebook Panels
Automotive Navigation, Heads-Up,
and Infotainment Displays
Industrial and Medical Displays
Ambient, Mood, and Accent Lighting
PART
MAX16807AUI+
TEMP RANGE
PIN-PACKAGE
-40°C to +125°C
28 TSSOP-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Pin Configuration appears at end of data sheet.
Typical Operating Circuits
VIN
VOUT
L
D
COUT
Q
R1
LEDs
CC2
RCS
CC1
RC1
R2
OUT CS AGND
VCC
3V TO 5.5V
COMP
CIN
FB
V+
CBYP
PGND
OUT0
OUT1
MAX16807
LE
DIN
OUT2
OUT3
CLK
OUT4
DOUT
OE
OUT5
OUT6
OUT7
SET
RTCT
REF
STAND-ALONE OPERATION
RT
RSET
CREF
CT
Typical Operating Circuits continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
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
MAX16807
General Description
MAX16807
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
ABSOLUTE MAXIMUM RATINGS
VCC to AGND..........................................................-0.3V to +30V
Current into VCC (VCC > 24V)...........................................±30mA
V+ to PGND..............................................................-0.3V to +6V
OUT to AGND.............................................-0.3V to (VCC + 0.3V)
OUT Current (10µs duration) .................................................±1A
FB, COMP, CS, RTCT, REF to AGND.......................-0.3V to +6V
COMP Sink Current.............................................................10mA
OUT0–OUT7 to PGND............................................-0.3V to +40V
DIN, CLK, LE, OE, SET to PGND..................-0.3V to (V+ + 0.3V)
DOUT Current...................................................................±10mA
OUT0–OUT7 Sink Current...................................................60mA
Total PGND Current ..........................................................480mA
Continuous Power Dissipation (TA = +70°C)
28-Pin TSSOP (derate 27mW/°C* above +70°C) .......2162mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
*Per JEDEC51 Standard (Multilayer Board).
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.
ELECTRICAL CHARACTERISTICS (PWM CONTROLLER)
(VCC = +15V, V+ = +3V to +5.5V referenced to PGND, RT = 10kΩ, CT = 3.3nF, REF = open, COMP = open, CREF = 0.1µF, VFB = 2V,
CS = AGND, VAGND = VPGND = 0V; all voltages are measured with respect to AGND, unless otherwise noted. TJ = TA = -40°C to
+125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5
5.05
V
0.4
4
mV
50
mV
REFERENCE
Output Voltage
VREF
Line Regulation
∆VLINE
IREF = 1mA, TJ = +25°C
12V< VCC < 25V, IREF = 1mA
Load Regulation
∆VLOAD
1mA < IREF < 20mA
4.95
6
Total Output-Voltage Variation
VREFT
(Note 2)
4.875
Output Noise Voltage
VNOISE
10Hz < f < 10kHz
Output Short-Circuit Current
ISHORT
VREF = 0V
30
Initial Accuracy
TJ = +25°C
51
Voltage Stability
12V < VCC < 25V
5.125
50
V
µV
180
mA
54
57
kHz
0.2
0.5
OSCILLATOR
Temperature Stability
RTCT Ramp Peak-to-Peak
RTCT Ramp Valley
%
1.7
V
1.1
Discharge Current
IDIS
Frequency Range
fOSC
%
1
V
VRTCT = 2V, TJ = +25°C
7.9
8.3
8.7
VRTCT = 2V, -40oC ≤ TJ ≤ +125°C
7.5
8.3
9.0
20
mA
1000
kHz
2.50
2.55
V
-0.01
-0.1
ERROR AMPLIFIER
FB Input Voltage
VFB
FB shorted to COMP
2.45
Input Bias Current
IB(FB)
Open-Loop Gain
AVOL
Unity-Gain Bandwidth
fGBW
Power-Supply Rejection Ratio
PSRR
12V ≤ VCC ≤ 25V
60
80
dB
COMP Sink Current
ISINK
VFB = 2.7V, VCOMP = 1.1V
2
6
mA
0.5
1.2
COMP Source Current
ISOURCE
2V ≤ VCOMP ≤ 4V
VFB = 2.3V, VCOMP = 5V
COMP Output-Voltage High
VOH
VFB = 2.3V, RCOMP = 15kΩ to AGND
COMP Output-Voltage Low
VOL
VFB = 2.7V, RCOMP = 15kΩ to VREF
2
5
µA
100
dB
1
MHz
1.8
5.8
0.1
_______________________________________________________________________________________
mA
V
1.1
V
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
(VCC = +15V, V+ = +3V to +5.5V referenced to PGND, RT = 10kΩ, CT = 3.3nF, REF = open, COMP = open, CREF = 0.1µF, VFB = 2V,
CS = AGND, VAGND = VPGND = 0V; all voltages are measured with respect to AGND, unless otherwise noted. TJ = TA = -40°C to
+125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CURRENT-SENSE AMPLIFIER
Current-Sense Gain
ACS
Maximum Current-Sense Signal
VCS_MAX
(Notes 3, 4)
2.85
3.00
3.40
V/V
(Note 3)
0.275
0.300
0.325
V
12V ≤ VCC ≤ 25V
70
VCOMP = 0V
-1
tPWM
50mV overdrive
60
OUT Low-Side On-Resistance
VRDS_ONL
ISINK = 200mA
OUT High-Side On-Resistance
VRDS_ONH
ISOURCE =
100mA
Power-Supply Rejection Ratio
PSRR
Current-Sense Input Bias Current
ICS
Current Sense to OUT Delay
dB
-2.5
µA
ns
MOSFET DRIVER
Source Current (Peak)
ISOURCE
CLOAD = 10nF
Sink Current (Peak)
TJ = -40°C to +85°C (Note 2)
4.5
10
TJ = -40°C to +125°C
4.5
12
TJ = -40°C to +85°C (Note 2)
3.5
7.5
TJ = -40°C to +125°C
3.5
10
2
Ω
Ω
A
ISINK
CLOAD = 10nF
1
A
Rise Time
tR
CLOAD = 1nF
15
ns
Fall Time
tF
CLOAD = 1nF
22
ns
UNDERVOLTAGE LOCKOUT/STARTUP
Startup Voltage Threshold
VCC_START
7.98
8.4
8.82
V
Minimum Operating Voltage After
Turn-On
VCC_MIN
7.1
7.6
8.0
V
Undervoltage-Lockout Hysteresis
UVLOHYST
0.8
V
PULSE-WIDTH MODULATION (PWM)
Maximum Duty Cycle
DMAX
Minimum Duty Cycle
DMIN
94.5
96
97.5
%
0
%
SUPPLY CURRENT
Startup Supply Current
VCC = 7.5V
32
65
µA
Operating Supply Current
ISTART
ICC
VFB = VCS = 0V
3
5
mA
VCC Zener Voltage
VZ
ICC = 25mA
24
26.5
V
_______________________________________________________________________________________
3
MAX16807
ELECTRICAL CHARACTERISTICS (PWM CONTROLLER) (continued)
MAX16807
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
ELECTRICAL CHARACTERISTICS (LED DRIVER)
(V+ = +3V to +5.5V, VAGND = VPGND = 0V; all voltages are measured with respect to PGND, unless otherwise noted. TA = TJ = -40°C
to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Operating Supply Voltage
Output Voltage
CONDITIONS
V+
MIN
TYP
3.0
VOUT_
MAX
UNITS
5.5
V
36
V
Standby Current (Interface Idle, All
Output Ports High Impedance)
RSET = 360Ω, DIN, LE, CLK = PGND or V+,
OE = V+, DOUT unconnected
3.6
4.5
mA
Standby Current
(Interface Active, All Output Ports
High Impedance)
RSET = 360Ω, fCLK = 5MHz, OE = V+,
DIN, LE = PGND or V+, DOUT unconnected
3.8
4.8
mA
RSET = 360Ω, OE = PGND, DIN,
LE = V+, DOUT unconnected
17
30
mA
Supply Current
(Interface Idle, All Output Ports
Active Low)
I+
INTERFACE (DIN, CLK, DOUT, LE, OE)
Input-Voltage High
(DIN, CLK, LE, OE)
VIH
Input-Voltage Low
(DIN, CLK, LE, OE)
VIL
Hysteresis Voltage
(DIN, CLK, LE, OE)
VHYST
Input Leakage Current
(DIN, CLK)
ILEAK
0.7
x V+
V
0.3
x V+
0.8
-1
V
V
+1
µA
OE Pullup Current to V+
IOE
V+ = 5.5V, OE = PGND
0.25
1.5
25.0
µA
LE Pulldown Current to PGND
ILE
V+ = 5.5V, LE = V+
0.25
1.5
25.0
µA
Output-Voltage High (DOUT)
VOH
ISOURCE = 4mA
Output-Voltage Low (DOUT)
VOL
ISINK = 4mA
OUT_ Output Current
OUT_ Leakage Current
4
IOUT_
0oC ≤ TA ≤ +125°C, VOUT = 1V to 2.5V, RSET =
360Ω
TA = -40°C, VOUT = 1V to 2.5V,
RSET = 360Ω
V+
- 0.5V
V
0.5
46.5
50
V
53.5
mA
43
OE = V+
_______________________________________________________________________________________
57
1
µA
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
(V+ = +4.5V to +5.5V, VAGND = VPGND = 0V; all voltages are measured with respect to PGND, unless otherwise noted. TA = TJ = -40°C
to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 5)
PARAMETER
SYMBOL
CONDITION
MIN
TYP
MAX
UNITS
INTERFACE TIMING CHARACTERISTICS
CLK Clock Period
tCP
40
ns
CLK Pulse-Width High
tCH
19
ns
CLK Pulse-Width Low
tCL
19
ns
DIN Setup Time
tDS
4
ns
DIN Hold Time
tDH
8
ns
DOUT Propagation Delay
tDO
50
ns
DOUT Rise Time
tDR
CDOUT = 10pF, 20% to 80%
10
ns
DOUT Fall Time
tDF
CDOUT = 10pF, 80% to 20%
10
ns
LE Pulse-Width High
tLW
20
LE Setup Time
tLS
15
LE Rising to OUT_ Rising Delay
12
ns
ns
tLRR
(Note 6)
110
ns
LE Rising to OUT_ Falling Delay
tLRF
(Note 6)
325
ns
CLK Rising to OUT_ Rising Delay
tCRR
(Note 6)
110
ns
CLK Rising to OUT_ Falling
Delay
tCRF
(Note 6)
325
ns
OE Rising to OUT_ Rising Delay
tOER
(Note 6)
110
ns
OE Falling to OUT_ Falling Delay
tOEF
(Note 6)
325
ns
OUT_ Turn-On Fall Time
tF
80% to 20% (Note 6)
210
ns
OUT_ Turn-Off Rise Time
tR
20% to 80% (Note 6)
130
ns
_______________________________________________________________________________________
5
MAX16807
5V TIMING CHARACTERISTICS
MAX16807
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
3.3V TIMING CHARACTERISTICS
(V+ = +3V to < +4.5V, VAGND = VPGND = 0V; all voltages are measured with respect to PGND, unless otherwise noted. TA = TJ = -40°C
to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 5)
PARAMETERS
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INTERFACE TIMING CHARACTERISTICS
CLK Clock Period
tCP
52
ns
CLK Pulse-Width High
tCH
24
ns
CLK Pulse-Width Low
tCL
24
ns
DIN Setup Time
tDS
4
ns
DIN Hold Time
tDH
8
ns
DOUT Propagation Delay
tDO
DOUT Rise Time
tDR
CDOUT = 10pF, 20% to 80%
DOUT Fall Time
tDF
CDOUT = 10pF, 80% to 20%
LE Pulse-Width High
tLW
20
ns
LE Setup Time
tLS
15
ns
12
70
ns
12
ns
12
ns
LE Rising to OUT_ Rising Delay
tLRR
(Note 6)
140
ns
LE Rising to OUT_ Falling Delay
tLRF
(Note 6)
350
ns
CLK Rising to OUT_ Rising Delay
tCRR
(Note 6)
140
ns
CLK Rising to OUT_ Falling Delay
tCRF
(Note 6)
350
ns
OE Rising to OUT_ Rising Delay
tOER
(Note 6)
140
ns
OE Falling to OUT_ Falling Delay
tOEF
(Note 6)
350
ns
OUT_ Turn-On Fall Time
tF
80% to 20% (Note 6)
275
ns
OUT_ Turn-Off Rise Time
tR
20% to 80% (Note 6)
150
ns
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
6
All devices are 100% production tested at TJ = +25°C and TJ = +125°C. Limits to TA = -40°C are guaranteed by design.
Guaranteed by design, not production tested.
Parameter is measured at trip point of latch with VFB = 0V.
Gain is defined as A = ∆VCOMP/∆VCS, 0.05V ≤ VCS ≤ 0.25V.
See Figures 3 and 4.
A 65Ω pullup resistor is connected from OUT_ to 5.5V. Rising refers to VOUT_ when current through OUT_ is turned off and
falling refers to VOUT_ when current through OUT_ is turned on.
_______________________________________________________________________________________
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
VCC FALLING
6
ICC (µA)
VCC (V)
7
VCC = 7.5V
39
5
4
5.1
CT = 560pF
4.9
37
4.7
35
4.5
ICC (mA)
8
41
MAX16807 toc02
VCC RISING
MAX16807 toc01
9
33
MAX16807 toc03
BOOTSTRAP UVLO vs. TEMPERATURE
10
OPERATING SUPPLY CURRENT
vs. TEMPERATURE AFTER STARTUP
(fOSC = fSW = 300kHz)
STARTUP CURRENT
vs. TEMPERATURE
4.3
31
4.1
29
3.9
27
3.7
3
2
HYSTERESIS
1
0
25
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
REFERENCE VOLTAGE
vs. TEMPERATURE
REFERENCE VOLTAGE
vs. REFERENCE LOAD CURRENT
REFERENCE VOLTAGE
vs. SUPPLY VOLTAGE
5.04
5.00
4.98
4.85
4.992
4.990
4.988
4.986
4.75
4.92
4.70
4.90
4.65
4.984
4.982
4.980
0
10
20
30
40
50
60
IREF (mA)
OSCILLATOR FREQUENCY (fOSC)
vs. TEMPERATURE
OSCILLATOR RT/CT DISCHARGE CURRENT
vs. TEMPERATURE
510
500
490
480
470
7.98
7.96
7.94
7.92
7.90
450
7.88
16
18
20
22
24
0.40
0.38
0.36
8.00
460
14
26
CURRENT-SENSE TRIP THRESHOLD
vs. TEMPERATURE
CS THRESHOLD (V)
520
VRT/CT = 2V
8.02
12
VCC (V)
MAX16807 toc08
530
8.04
RT/CT DISCHARGE CURRENT (mA)
MAX16807 toc07
TEMPERATURE (°C)
RT = 3.65kΩ
CT = 560pF
10
70
MAX16807 toc09
4.94
-40 -25 -10 5 20 35 50 65 80 95 110 125
OSCILLATOR FREQUENCY (kHz)
4.994
4.90
4.80
IREF = 20mA
4.96
540
4.996
VREF (V)
VREF (V)
VREF (V)
IREF = 1mA
5.00
IREF = 1mA
4.998
4.95
5.02
MAX16807 toc06
5.06
5.000
MAX16807 toc05
5.05
MAX16807 toc04
5.08
550
3.5
-40 -25 -10 5 20 35 50 65 80 95 110 125
0.34
0.32
0.30
0.28
0.26
0.24
0.22
0.20
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
7
MAX16807
Typical Operating Characteristics
(VCC = +15V, V+ = 3V to 5.5V, RT = 10kΩ, CT = 3.3nF, VREF = COMP = open, CREF = 0.1µF, VFB = 2V, VCS = VAGND = VPGND = 0V.
Typical values are at TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VCC = +15V, V+ = 3V to 5.5V, RT = 10kΩ, CT = 3.3nF, VREF = COMP = open, CREF = 0.1µF, VFB = 2V, VCS = VAGND = VPGND = 0V.
Typical values are at TA = +25°C, unless otherwise noted.)
CT = 560pF
CT = 100pF
10
1
RDS_ON (Ω)
CT = 10nF
CT = 4.7nF
CT = 3.3nF
CT = 2.2nF
0.1
10
ISINK = 200mA
9
8
7
6
5
4
3
2
1
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
FREQUENCY (Hz)
TEMPERATURE (°C)
TEMPERATURE (°C)
PROPAGATION DELAY FROM CURRENT-LIMIT
COMPARATOR TO OUT vs. TEMPERATURE
ERROR-AMPLIFIER OPEN-LOOP GAIN
AND PHASE vs. FREQUENCY
COMP VOLTAGE LEVEL TO TURN
OFF DEVICE vs. TEMPERATURE
1M
10M
MAX16807 toc14
80
100
GAIN (dB)
60
50
40
30
20
-65
PHASE
60
1.7
0
-165
1.6
-190
10k 100k 1M 10M 100M
1.5
0.01 1
10 100 1k
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
FREQUENCY (Hz)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS OFF, RSET = 720Ω)
2.00
MAX16807 toc16
7.0
CT = 100pF
6.0
5.5
ICC (mA)
1.8
-140
SUPPLY CURRENT
vs. OSCILLATOR FREQUENCY
4.0
1.9
20
TEMPERATURE (°C)
4.5
2.0
-115
-20
5.0
-90
2.1
40
-40 -25 -10 5 20 35 50 65 80 95 110 125
6.5
-40
GAIN
80
10
0
VCC = 15V
2.2
-15
120
70
2.3
10
VCOMP (V)
90
140
PHASE (DEGREES)
MAX16807 toc13
100
TA = +125°C
TA = -40°C
3.5
TA = +125°C
MAX16807 toc17
100k
TA = +85°C
1.95
TA = +25°C
1.90
TA = -40°C
1.85
3.0
2.5
1.80
2.0
20 120 220 320 420 520 620 720 820 920 1020
FREQUENCY (kHz)
8
3.0
3.5
MAX16807 toc15
-40 -25 -10 5 20 35 50 65 80 95 110 125
10k
SUPPLY CURRENT (mA)
RT (kΩ)
CT = 220pF
ISOURCE = 100mA
MAX16807 toc12
CT = 1nF
5.0
4.8
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
2.4
2.2
2.0
RDS_ON (Ω)
MAX16807 toc10
1000
100
OUT IMPEDANCE vs. TEMPERATURE
(RDS_ON NMOS DRIVER)
OUT IMPEDANCE vs. TEMPERATURE
(RDS_ON PMOS DRIVER)
MAX16807 toc11
TIMING RESISTANCE
vs. OSCILLATOR FREQUENCY
PROPAGATION DELAY (ns)
MAX16807
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
MAX16807 toc18
20
TA = +125°C
3.65
TA = +85°C
3.60
TA = +25°C
TA =-40°C
3.55
TA = +125°C TA = +85°C
17
SUPPLY CURRENT (mA)
14
11
TA = -40°C
8
3.50
TA = +25°C
5
3.0
3.5
4.0
4.5
5.0
5.5
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS ON, RSET = 360Ω)
OUT_ CURRENT vs. OUT_ VOLTAGE
(RSET = 720Ω, V+ = 3.3V)
19
16
13
25
TA = +25°C
TA = -40°C
TA = +25°C
20
15
TA = +85°C
TA = +125°C
10
5
TA = -40°C
0
10
3.0
3.5
4.0
4.5
5.0
0
5.5
0.5
1.0
1.5
2.0
2.5
SUPPLY VOLTAGE (V)
OUT_ VOLTAGE (V)
OUT_ CURRENT vs. OUT_ VOLTAGE
(RSET = 360Ω, V+ = 3.3V)
OUT_ CURRENT vs. OUT_ VOLTAGE
(RSET = 720Ω, V+ = 5.0V)
30
MAX16807 toc22
60
40
TA = -40°C
TA = +25°C
30
20
TA = +85°C
TA = +125°C
10
25
OUT_ CURRENT (mA)
50
OUT_ CURRENT (mA)
MAX16807 toc21
TA = +125°C TA = +85°C
OUT_ CURRENT (mA)
SUPPLY CURRENT (mA)
22
30
MAX16807 toc20
25
5.5
3.0
MAX16807 toc23
SUPPLY CURRENT (mA)
3.70
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS ON, RSET = 720Ω)
MAX16807 toc19
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(INTERFACE IDLE, ALL OUTPUTS OFF, RSET = 360Ω)
20
TA = -40°C
TA = +25°C
15
TA = +85°C
10
TA = +125°C
5
0
0
0
0.5
1.0
1.5
2.0
OUT_ VOLTAGE (V)
2.5
3.0
0
0.5
1.0
1.5
2.0
2.5
3.0
OUT_ VOLTAGE (V)
_______________________________________________________________________________________
9
MAX16807
Typical Operating Characteristics (continued)
(VCC = +15V, V+ = 3V to 5.5V, RT = 10kΩ, CT = 3.3nF, VREF = COMP = open, CREF = 0.1µF, VFB = 2V, VCS = VAGND = VPGND = 0V.
Typical values are at TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VCC = +15V, V+ = 3V to 5.5V, RT = 10kΩ, CT = 3.3nF, VREF = COMP = open, CREF = 0.1µF, VFB = 2V, VCS = VAGND = VPGND = 0V.
Typical values are at TA = +25°C, unless otherwise noted.)
OUT_ CURRENT vs. SUPPLY VOLTAGE V+
(RSET = 720Ω, VOUT = 2V)
OUT_ CURRENT vs. OUT_ VOLTAGE
(RSET = 360Ω, V+ = 5.0V)
50
MAX16807 toc25
26.0
MAX16807 toc24
60
40
OUT_ CURRENT (mA)
OUT_ CURRENT (mA)
25.5
TA = -40°C
TA = +25°C
30
TA = +85°C
20
TA = +125°C
TA = +85°C
TA = +125°C
25.0
TA = +25°C
24.5
TA = -40°C
10
24.0
0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.0
3.5
5.5
TA = +125°C
50
TA = +25°C
TA = -40°C
MAX16807 toc27
40
OUT_ CURRENT (mA)
TA = +85°C
30
20
10
0
48
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
10
5.0
50
MAX16807 toc26
52
49
4.5
OUT_ CURRENT vs. SET RESISTANCE
(V+ = 5.0V)
OUT_ CURRENT vs. SUPPLY VOLTAGE V+
(RSET = 360Ω, VOUT = 2V)
51
4.0
SUPPLY VOLTAGE (V)
OUT_ VOLTAGE (V)
OUT_ CURRENT (mA)
MAX16807
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
5.0
5.5
0
1
2
3
RSET (kΩ)
______________________________________________________________________________________
4
5
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
PIN
NAME
1, 13, 28
N.C.
FUNCTION
2
AGND
3
OUT
MOSFET Driver Output OUT. Connects to the gate of the external n-channel MOSFET.
4
VCC
Power-Supply Input. Bypass VCC to AGND with a 0.1µF ceramic capacitor or a parallel combination
of a 0.1µF and a higher value ceramic capacitor.
5V Reference Output. Bypass REF to AGND with a 0.1µF ceramic capacitor.
No Connection. Not internally connected. Leave unconnected.
Analog Ground
5
REF
6–9
OUT4–OUT7
10
OE
11
DOUT
12
SET
LED Current Setting. Connect RSET from SET to PGND to set the LED current.
14
V+
LED Driver Positive Supply Voltage. Bypass V+ to PGND with a 0.1µF ceramic capacitor.
15, 16
PGND
17
DIN
Serial-Data Input
18
CLK
Serial-Clock Input
19
LE
20–23
OUT0–OUT3
24
COMP
25
FB
Error-Amplifier Inverting Input
26
CS
PWM Controller Current-Sense Input
27
RTCT
—
EP
LED Driver Outputs. OUT4–OUT7 are open-drain, constant-current-sinking outputs rated for 36V.
Active-Low Output Enable Input. Drive OE low to PGND to enable the OUT0–OUT7. Drive OE high to
disable OUT0–OUT7.
Serial-Data Output. Data is clocked out of the 8-bit internal shift register to DOUT on CLK’s rising
edge.
Power Ground
Latch-Enable Input. Data is loaded transparently from the internal shift register(s) to the output
latch(es) while LE is high. Data is latched into the output latch(es) on LE’s falling edge, and retained
while LE is low.
LED Driver Outputs. OUT0–OUT3 are open-drain, constant-current-sinking outputs rated for 36V.
Error-Amplifier Output
PWM Controller Timing Resistor/Capacitor Connection. A resistor RT from RTCT to REF and a
capacitor CT from RTCT to AGND set the oscillator frequency.
Exposed Paddle. Connect to the ground plane for improved power dissipation. Do not use as the
only ground connection for the part.
Detailed Description
The MAX16807 LED driver includes an internal switchmode controller that can be used as boost or buckboost (SEPIC) converters to generate the voltage
necessary to drive the multiple strings of LEDs. This
device incorporates an integrated low-side driver, a
programmable oscillator (20kHz to 1MHz), an error
amplifier, a low-voltage (300mV) current sense for higher efficiency, and a 5V reference to power up external
circuitry (see Figures 1a, 1b, and 1c).
The MAX16807 LED driver includes a 4-wire serial
interface and a current-mode PWM controller to generate the necessary voltage for driving eight open-drain,
constant-current-sinking output ports. The driver uses
current-sensing feedback circuitry (not simple current
mirrors) to ensure very small current variations over the
full allowed range of output voltage (see the Typical
Operating Characteristics). The 4-wire serial interface
comprises an 8-bit shift register and an 8-bit transparent latch. The shift register is written through a clock
input, CLK, and a data input, DIN, and the data propagates to a data output, DOUT. The data output allows
multiple drivers to be cascaded and operated together.
The contents of the 8-bit shift register are loaded into
the transparent latch through a latch-enable input, LE.
The latch is transparent to the shift register outputs
when high and latches the current state on the falling
edge of LE. Each driver output is an open-drain, constant-current sink that should be connected to the cath-
______________________________________________________________________________________
11
MAX16807
Pin Description
ode of a string of LEDs connected in series. The constant-current capability is up to 55mA per output, set
for all 8 outputs by an external resistor, R SET . The
device can operate in a stand-alone mode (see the
Typical Operating Circuits.)
The number of channels can be expanded by using the
MAX6970 and MAX6971 family in conjunction with the
MAX16807.
UVLO
MAX16807
REFERENCE
2.5V
VOLTAGEDIVIDER
PREREG
5V
VCC
26.5V
THERMAL
SHUTDOWN
EN_REF
BG
VDD
REF
5V REG
SNS
REG_OK
DELAY
VOLTAGE
DIVIDER
AGND
VCC
300mV
ILIM
S
R
OUT
Q
CS
CPWM
2R
VEA
CLK
FB
COMP
R
OSC
Q
RTCT
CLK
SERIAL-TO-PARALLEL SHIFT REGISTER
DIN
D0
D1
D2
D3
D4
D5
D6
D7
D5
D6
D7
DOUT
OUTPUT LATCHES
LE
D0
D1
D2
D3
D4
POWER-ON
RESET
V+
OE
V+
CONSTANT-CURRENT SINK
THERMAL
SHUTDOWN
D0
D1
D2
D3
D4
D5
D6
D7
CURRENT
REFERENCE
OUT7
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
PGND
OUT0
MAX16807
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
Figure 1a. Internal Block Diagram (MAX16807)
12
______________________________________________________________________________________
SET
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
68W/L
1.23V
W/L
OUT_
1.23
REST
995R
R
SET
PGND
Figure 1c. OUT_ Driver Internal Diagram
Switch-Mode Controller
Current-Mode Control Loop
The advantages of current-mode control over voltagemode control are twofold. First, there is the feed-forward characteristic brought on by the controller’s ability
to adjust for variations in the input voltage on a cycleby-cycle basis. Second, the stability requirements of
the current-mode controller are reduced to that of a single pole system unlike the double pole in the voltagemode control scheme. The MAX16807 uses a
current-mode control loop where the output of the error
amplifier is compared to the current-sense voltage
(VCS). When the current-sense signal is lower than the
inverting input of the CPWM comparator, the output of
the comparator is low and the switch is turned on at
each clock pulse. When the current-sense signal is
higher than the inverting input of the CPWM comparator, the output is high and the switch is turned off.
Undervoltage Lockout (UVLO)
The turn-on supply voltage for the MAX16807 is 8.4V
(typ). Once VCC reaches 8.4V, the reference powers up.
There is a 0.8V of hysteresis from the turn-on voltage to
the UVLO threshold. Once V CC reaches 8.4V, the
MAX16807 operates with VCC down to 7.6V (typ). Once
VCC goes below 7.6V, the device is in UVLO. When in
UVLO, the quiescent supply current into VCC falls back
to 32µA (typ), and OUT and REF are pulled low.
MOSFET Driver
OUT drives an external n-channel MOSFET and swings
from AGND to VCC. Ensure that VCC remains below the
absolute maximum VGS rating of the external MOSFET.
OUT is a push-pull output with the on-resistance of the
pMOS typically 3.5Ω and the on-resistance of the
nMOS typically 4.5Ω. The driver can source 2A and
sink 1A typically. This allows for the MAX16807 to
quickly turn on and off high gate-charge MOSFETs.
Bypass VCC with one or more 0.1µF ceramic capacitors
to AGND, placed close to the VCC pin. The average
current sourced to drive the external MOSFET depends
on the total gate charge (QG) and operating frequency
of the converter. The power dissipation in the
MAX16807 is a function of the average output drive
current (IDRIVE). Use the following equation to calculate
the power dissipation in the device due to IDRIVE:
IDRIVE = (QG x fSW)
PD = (IDRIVE + ICC) x VCC
where I CC is the operating supply current. See the
Typical Operating Characteristics for the operating
supply current at a given frequency.
Error Amplifier
The MAX16807 includes an internal error amplifier. The
inverting input is at FB and the noninverting input is
internally connected to a 2.5V reference. Set the output
voltage using a resistive divider between output of the
converter VOUT, FB, and AGND. Use the following formula to set the output voltage:
R1 ⎞
⎛
VOUT = ⎜1 +
⎟ x VFB
⎝
R2 ⎠
where VFB = 2.5V.
Oscillator
The oscillator frequency is programmable using an
external capacitor and a resistor at RTCT (see RT and
CT in the Typical Operating Circuits). RT is connected
from RTCT to the 5V reference (REF), and CT is connected from RTCT to AGND. REF charges CT through
RT until its voltage reaches 2.8V. CT then discharges
through an 8.3mA internal current sink until CT’s voltage
reaches 1.1V, at which time CT is allowed to charge
through RT again. The oscillator’s period is the sum of
the charge and discharge times of CT. Calculate the
charge time as follows:
tC = 0.57 x RT x CT
where t C is in seconds, R T in ohms (Ω), and C T in
Farads (F).
The discharge time is then:
tD = (RT x CT x 1000) / [(4.88 x RT) - (1.8 x 1000)]
where t D is in seconds, R T in ohms (Ω), and C T in
Farads (F).
______________________________________________________________________________________
13
MAX16807
V+
MAX16807
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
The oscillator frequency is then:
RCS =
1
fOSC =
t
+
( C tD)
Reference Output
REF is a 5V reference output that can source 20mA.
Bypass REF to AGND with a 0.1µF capacitor.
Current Limit
The MAX16807 includes a fast current-limit comparator
to terminate the on cycle during an overload or a fault
condition. The current-sense resistor, RCS, connected
between the source of the external MOSFET and
AGND, sets the current limit. The CS input has a voltage trip level (VCS) of 0.3V. Use the following equation
to calculate RCS:
VIN
C1
L1
VCS
IP − P
IP-P is the peak current that flows through the MOSFET.
When the voltage produced by this current (through the
current-sense resistor) exceeds the current-limit comparator threshold, the MOSFET driver (OUT) turns the
switch off within 60ns. In most cases, a small RC filter is
required to filter out the leading-edge spike on the sense
waveform. Set the time constant of the RC filter at 50ns.
Buck-Boost (SEPIC) Operation
Figure 2 shows a buck-boost application circuit using
the MAX16807 in a stand-alone mode of operation.
SEPIC topology is necessary when the total forward
voltage of the LEDs in a string is such that VOUT can be
below or above VIN.
VOUT
D
COUT
L2
Q
R1
CC2
RCS
CC1
RC1
R2
OUT CS AGND
COMP
VCC
FB
CIN
3V TO 5.5V
V+
CBYP
MAX16807
OUT0
PGND
OUT1
OUT2
DIN
LE
OUT3
OUT4
EXTERNAL
CLOCK INPUT
EXTERNAL
DIM INPUT
OUT5
CLK
DOUT
OE
SET
OUT6
OUT7
RTCT
REF
RT
RSET
CREF
CT
Figure 2. Buck-Boost (SEPIC) Configuration
14
______________________________________________________________________________________
LEDs
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
CLK. Data at DIN propagates through the shift register
and appears at DOUT eight clock cycles later. Table 1
shows the 4-wire serial-interface truth table.
4-Wire Interface
The MAX16807 also operates in a stand-alone mode
(see the Typical Operating Circuits). For use with a
microcontroller, the MAX16807 features a 4-wire serial
interface using DIN, CLK, LE, OE inputs and DOUT as
a data output. This interface is used to write the LED
channels’ data to the MAX16807. The serial-interface
data word length is 8 bits, D0–D7. See Figure 3.
The functions of the five interface pins are as follows:
DIN is the serial-data input, and must be stable when it
is sampled on the rising edge of CLK. Data is shifted in
MSB first. This means that data bit D7 is clocked in first,
followed by 7 more data bits, finishing with the LSB, D0.
Selecting External Component
RSET to Set LED Output Current
The MAX16807 uses an external resistor, RSET, to set
the LED current for outputs OUT0–OUT7. The minimum
allowed value of RSET is 330Ω, which sets the output
currents to 55mA. The maximum allowed value of RSET
is 5kΩ (IOUT_ = 3.6mA) and maximum allowed capacitance at SET is 100pF.
Use the following formula to set the output current:
RSET =
CLK is the serial-clock input that shifts data at DIN into
the MAX16807’s 8-bit shift register on its rising edge.
LE is the latch enable input of the MAX16807 that transfers data from the 8-bit shift register to its 8-bit output
latch (transparent latch). The data is latched on the
falling edge of LE (Figure 4). The fourth input (OE) provides output-enable control of the output drivers. When
OE is driven high, the outputs (OUT0–OUT7) are forced
to high impedance without altering the contents of the
output latches. Driving OE low enables the outputs to
follow the state of the output latches. OE is independent of the operation of the serial interface operation.
Data can be shifted into the serial-interface shift register and latched, regardless of the state of OE. DOUT is
the serial-data output that shifts data out from the
MAX16807’s 8-bit shift register on the rising edge of
18, 000
IOUT _
where IOUT_ is the desired output current in milliamps
and the value for RSET is in ohms.
Overtemperature Cutoff
The MAX16807 contains an internal temperature sensor
that turns off all outputs when the die temperature
exceeds +165°C. The outputs are enabled again when
the die temperature drops below +140°C. Register contents are not affected, so when a driver is overdissipating, the external symptom is the load LEDs cycling on
and off as the driver repeatedly overheats and cools,
alternately turning itself off and then back on again.
Table 1. 4-Wire Serial-Interface Truth Table
BLANKING
OUTPUT CONTENTS
SERIAL CLOCK SHIFT REGISTER CONTENTS LOAD
LATCH CONTENTS
INPUT
INPUT
CURRENT AT OUT_
DATA INPUT
INPUT
CLK D0 D1 D2 … Dn-1 Dn
LE
D0 D1 D2 … Dn-1 Dn
OE
D0 D1 D2 … Dn-1 Dn
DIN
H
H
R0 R1 … Rn-2 Rn-1
L
L
R0 R1 … Rn-2 Rn-1
X
R0
R1 R2 … Rn-1
X
X
X
…
X
P0
P1
P2 … Pn-1
Rn
X
L
R0 R1 R2
… Rn-1 Rn
Pn
H
P0
P1
P2
… Pn-1 Pn
L
P0
X
X
X
…
H
L
X
X
P1 P2
L
L
…
Pn-1
Pn
…
L
L
L = Low Logic Level
H = High Logic Level
X = Don’t Care
P = Present State (Shift Register)
R = Previous State (Latched)
______________________________________________________________________________________
15
MAX16807
LED Driver
MAX16807
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
LE
tLW
tCL
tCH
tLS
tCP
CLK
tDH
tDS
D0
D7
DIN
tDO
D7
DOUT
tOEW
OE
tOEF
tOER
80%
OUT_
20%
tf
tr
Figure 3. 4-Wire Serial-Interface Timing Diagram
Stand-Alone Operation
LE
tLRF
OUT_
LE
tLRR
OUT_
In stand-alone operation, the MAX16807 does not use
the 4-wire interface (see the Typical Operating
Circuits). Connecting DIN and LE to V+ provides at
least 8 external clock pulses to CLK to enable 8 outputs. This startup pulse sequence can be provided
either using an external clock or the PWM signal. The
external clock can also be generated using the signal
at RTCT and an external comparator.
LED Dimming
PWM Dimming
CLK
tCRF
OUT_
CLK
tCRR
OUT_
All the output channels can be dimmed simultaneously
by applying a PWM signal (50Hz to 30kHz) to OE. This
allows for a wide range of dimming up to a 5000:1 ratio.
Each channel can be independently turned on and off
using a 4-wire serial interface. The dimming is proportional to the PWM duty cycle.
LED Current Amplitude Adjustment
Using an analog or digital potentiometer as RSET allows
for LED current amplitude adjustment and linear dimming.
Figure 4. LE and CLK to OUT_ Timing
16
______________________________________________________________________________________
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching
losses and clean, stable operation. Use a multilayer
board whenever possible for better noise immunity.
Protect sensitive analog grounds by using a star
ground configuration. Minimize ground noise by connecting AGND, PGND, the input bypass-capacitor
ground lead, and the output-filter ground lead to a single point (star ground configuration). Also, minimize
trace lengths to reduce stray capacitance, trace resistance, and radiated noise. The trace between the output voltage-divider and the FB pin must be kept short,
as well as the trace between AGND and PGND.
i = 7
⎡
⎤
PD = DUTY x ⎢(V + x I+) + ∑ VOUTi x IOUTi⎥ + (VCC x ICC)
⎢⎣
⎥⎦
i = 0
where:
V+ = supply voltage
I+ = operating supply current
DUTY = PWM duty cycle applied to OE
VOUTi = MAX16807 port output voltage when driving
load LED(s)
IOUTi = LED drive current programmed by RSET
PD = power dissipation.
Pin Configuration
Chip Information
PROCESS: BiCMOS
TOP VIEW
+
N.C. 1
28 N.C.
27 RTCT
AGND 2
OUT 3
VCC 4
26 CS
MAX16807
REF 5
25 FB
24 COMP
OUT4 6
23 OUT3
OUT5 7
22 OUT2
OUT6 8
21 OUT1
OUT7 9
20 OUT0
OE 10
19 LE
DOUT 11
18 CLK
SET 12
17 DIN
N.C. 13
16 PGND
V+ 14
15 PGND
TSSOP-EP
______________________________________________________________________________________
17
MAX16807
Computing Power Dissipation
Use the following equation to estimate the upper limit
power dissipation (PD) for the MAX16807:
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
MAX16807
Typical Operating Circuits (continued)
VIN
L
VOUT
D
COUT
Q
LEDs
R1
CC2
RCS
CC1
RC1
R2
OUT CS AGND
COMP
VCC
FB
CIN
3V TO 5.5V
V+
CBYP
OUT0
PGND
OUT1
MAX16807
OUT2
OUT3
OUT4
SCLK
MOSI
MISO
µC
LOAD
ENABLE
OUT5
CLK
DIN
DOUT
LE
OE
SET
RSET
OUT6
OUT7
OPERATION WITH MICROCONTROLLER
RTCT
REF
RT
CREF
CT
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. Package drawings may show a different suffix character, but the drawing pertains to the
package regardless of RoHS status.)
18
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
28 TSSOP
U28ME+1
21-0108
______________________________________________________________________________________
Integrated 8-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller
REVISION
NUMBER
REVISION
DATE
0
10/06
Initial release
—
1
4/07
Release of the MAX16808
1
2
8/09
Removal of the MAX16808 from the data sheet.
DESCRIPTION
PAGES
CHANGED
1–21
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19
© 2009 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX16807
Revision History