EVALUATION KIT AVAILABLE
MAX16821A/MAX16821B/
MAX16821C
High-Power Synchronous HBLED
Drivers with Rapid Current Pulsing
General Description
The MAX16821A, MAX16821B, and MAX16821C pulse-
width-modulation (PWM) LED driver controllers provide
high output-current capability in a compact package with a
minimum number of external components. The
MAX16821A–MAX16821C are suitable for use in synchro-
nous and nonsynchronous step-down (buck), boost, buck-
boost, SEPIC, and Cuk LED drivers. A logic input (MODE)
allows the devices to switch between synchronous buck
and boost modes of operation. These devices are the first
high-power drivers designed specifically to accommodate
common-anode HB LEDs.
The ICs offer average current-mode control that enable
the use of MOSFETs with optimal charge and on-
resistance figure of merit, thus minimizing the need for
external heatsinking even when delivering up to 30A of
LED current.
The differential sensing scheme provides accurate control
of the LED current. The ICs operate from a 4.75V to 5.5V
supply range with the internal regulator disabled (V
CC
connected to IN). These devices operate from a 7V to 28V
input supply voltage with the internal regulator enabled.
The MAX16821A–MAX16821C feature a clock output
with 180° phase delay to control a second out-of-phase
LED driver to reduce input and output filter capacitor size
and to minimize ripple currents. The wide switching fre-
quency range (125kHz to 1.5MHz) allows the use of small
inductors and capacitors.
Additional features include programmable overvoltage
protection and an output enable function.
Features
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Ordering Information
PART
MAX16821AATI+
MAX16821BATI+
MAX16821CATI+
Up to 30A Output Current
True-Differential Remote Output Sensing
Average Current-Mode Control
4.75V to 5.5V or 7V to 28V Input Voltage Range
0.1V/0.03V LED Current-Sense Options Maximize
Efficiency (MAX16821B/MAX16821C)
Thermal Shutdown
Nonlatching Output-Overvoltage Protection
Low-Side Buck Mode with or without Synchronous
Rectification
High-Side Buck and Low-Side Boost Mode with or
without Synchronous Rectification
125kHz to 1.5MHz Programmable/Synchronizable
Switching Frequency
Integrated 4A Gate Drivers
Clock Output for 180° Out-of-Phase Operation for
Second Driver
-40°C to +125°C Operating Temperature Range
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
28 TQFN-EP*
28 TQFN-EP*
28 TQFN-EP*
+Denotes lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Simplified Diagram
7V TO 28V
C1
DH
Q1
L1
V
LED
Applications
●
Front Projectors/Rear-Projection TVs
●
Portable and Pocket Projectors
●
LCD TVs and Display Backlight
EN
I.C.
IN
MAX16821
DL
Q2
C2
Q3
OVI
CSP
PGND
R1
Typical Operating Circuit
and
Selector Guide
appears at
end of data sheet.
CLP
HIGH-FREQUENCY
PULSE TRAIN
19-0881; Rev 3; 4/14
MAX16821A/MAX16821B/
MAX16821C
Absolute Maximum Ratings
IN to SGND ...........................................................-0.3V to +30V
BST to SGND ........................................................-0.3V to +35V
BST to LX ................................................................-0.3V to +6V
DH to LX .......................................-0.3V to (VBST - VLX) + 0.3V
DL to PGND .............................................-0.3V to (VDD + 0.3V)
V
CC
to SGND ..........................................................-0.3V to +6V
V
CC
, V
DD
to PGND .................................................-0.3V to +6V
SGND to PGND....................................................-0.3V to +0.3V
V
CC
Current .....................................................................300mA
High-Power Synchronous HBLED
Drivers with Rapid Current Pulsing
All Other Pins to SGND ............................ -0.3V to (V
CC
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
28-Pin TQFN 5mm x 5mm (derate 34.5mW/°C
above +70°C) ...........................................................2758mW
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
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
(V
CC
= 5V, V
DD
= V
CC
, T
A
= T
J
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Input-Voltage Range
Quiescent Supply Current
LED CURRENT REGULATOR
V
IN
= V
CC
= 4.75V to 5.5V, f
SW
= 500kHz
(MAX16821A)
V
IN
= 7V to 28V, f
SW
= 500kHz
(MAX16821A)
Differential Set Value
(V
SENSE
+ to V
SENSE
-)
(Note 2)
V
IN
= V
CC
= 4.75V to 5.5V,
f
SW
= 500kHz (MAX16821B)
V
IN
= 7V to 28V, f
SW
= 500kHz
(MAX16821B)
V
IN
= V
CC
= 4.75V to 5.5V,
f
SW
= 500kHz (MAX16821C)
V
IN
= 7V to 28V, f
SW
= 500kHz
(MAX16821C)
Soft-Start Time
STARTUP/INTERNAL REGULATOR
V
CC
Undervoltage Lockout
(UVLO)
UVLO Hysteresis
V
CC
Output Voltage
MOSFET DRIVER
Output Driver Impedance
Output Driver Source/Sink
Current
Nonoverlap Time
I
DH
, I
DL
t
NO
C
DH/DL
= 5nF
Low or high output, I
SOURCE/SINK
= 20mA
1.1
4
35
3
Ω
A
ns
UVLO
V
CC
rising
V
CC
falling
V
IN
= 7V to 28V, I
SOURCE
= 0 to 60mA
4.85
4.1
4.3
200
5.10
5.30
4.5
V
mV
V
t
SS
0.594
0.594
0.098
0.098
0.028
0.028
0.600
0.600
0.100
0.100
0.030
0.030
1024
0.606
0.606
0.102
V
0.102
0.032
0.032
Clock
Cycles
SYMBOL
V
IN
I
Q
CONDITIONS
Internal LDO on
Internal LDO off (V
CC
connected to V
IN
)
V
EN
= V
CC
or SGND, no switching
MIN
7
4.75
2.7
TYP
MAX
28
5.50
5.5
V
mA
UNITS
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Maxim Integrated
│
2
MAX16821A/MAX16821B/
MAX16821C
Electrical Characteristics (continued)
High-Power Synchronous HBLED
Drivers with Rapid Current Pulsing
(V
CC
= 5V, V
DD
= V
CC
, T
A
= T
J
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
OSCILLATOR
Switching Frequency Range
R
T
= 500kΩ
Switching Frequency
f
SW
R
T
= 120kΩ
R
T
= 39.9kΩ
Switching Frequency Accuracy
CLKOUT Phase Shift with
Respect to DH (Rising Edges)
CLKOUT Phase Shift with
Respect to DL (Rising Edges)
CLKOUT Output-Voltage Low
CLKOUT Output-Voltage High
SYNC Input High Pulse Width
SYNC Input Clock High
Threshold
SYNC Input Clock Low
Threshold
SYNC Pullup Current
SYNC Power-Off Level
INDUCTOR CURRENT LIMIT
Average Current-Limit Threshold
Reverse Current-Limit Threshold
Cycle-by-Cycle Current Limit
Cycle-by-Cycle Overload
CURRENT-SENSE AMPLIFIER
CSP to CSN Input Resistance
Common-Mode Range
Input Offset Voltage
Amplifier Voltage Gain
3dB Bandwidth
Transconductance
Open-Loop Gain
R
CS
V
CMR(CS)
V
OS(CS)
A
V(CS)
f
3dB
g
m
A
VL(CE)
V
IN
= 7V to 28V
0
0.1
34.5
4
550
50
4
5.5
kΩ
V
mV
V/V
MHz
µS
dB
V
CL
V
CLR
CSP to CSN
CSP to CSN
CSP to CSN
V
CSP
to V
CSN
= 75mV
26.4
27.5
-2.0
60
260
33.0
mV
mV
mV
ns
V
OL
V
OH
t
SYNC
V
SYNCH
V
SYNCL
I
SYNC_
OUT
OFF
SYMBOL
CONDITIONS
MIN
125
120
495
1515
-5
-8
TYP
MAX
1500
UNITS
kHz
kHz
125
521
1620
130
547
1725
+5
+8
%
120kΩ < R
T
≤ 500kΩ
40kΩ ≤ R
T
≤ 120kΩ
f
SW
= 125kHz, MODE connected
to SGND
f
SW
= 125kHz, MODE connected
to V
CC
I
SINK
= 2mA
I
SOURCE
= 2mA
180
degrees
180
0.4
4.5
200
2
0.4
V
V
ns
V
V
µA
V
V
RT/SYNC
= 0V
250
500
0.4
V
SYNC_
CURRENT-ERROR AMPLIFIER (TRANSCONDUCTANCE AMPLIFIER)
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Maxim Integrated
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3
MAX16821A/MAX16821B/
MAX16821C
Electrical Characteristics (continued)
High-Power Synchronous HBLED
Drivers with Rapid Current Pulsing
(V
CC
= 5V, V
DD
= V
CC
, T
A
= T
J
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Common-Mode Voltage Range
DIFF Output Voltage
Input Offset Voltage
SYMBOL
V
CMR
(DIFF)
CONDITIONS
MIN
0
TYP
MAX
1.0
UNITS
V
V
LED CURRENT SIGNAL DIFFERENTIAL VOLTAGE AMPLIFIER (DIFF)
V
CM
V
OS(DIFF)
A
V(DIFF)
V
SENSE+
= V
SENSE-
= 0V
MAX16821A
MAX16821B/MAX16821C
MAX16821A
MAX16821B
MAX16821C
MAX16821A, C
DIFF
= 20pF
-3.7
-1.5
0.992
5.85
18.5
0.6
+3.7
+1.5
1
6
20
1.7
1600
550
50
30
10
100
60
20
4
1
30
80
50
1.008
6.1
21.5
mV
Amplifier Voltage Gain
V/V
MHz
kHz
3dB Bandwidth
f
3dB
MAX16821B, C
DIFF
= 20pF
MAX16821C, C
DIFF
= 20pF
MAX16821A
SENSE+ to SENSE- Input
Resistance
OUTV AMPLIFIER
Gain-Bandwidth Product
3dB Bandwidth
Output Sink Current
Output Source Current
Maximum Load Capacitance
OUTV to (CSP - CSN) Transfer
Function
Input Offset Voltage
R
VS
MAX16821B
MAX16821C
V
OUTV
= 2V
V
OUTV
= 2V
kΩ
MHz
MHz
µA
µA
pF
137.7
V/V
mV
dB
MHz
+0.2
940
µA
mV
4mV ≤ C
SP
– C
SN
≤ 32mV
132.5
135
1
VOLTAGE-ERROR AMPLIFIER (EAOUT)
Open-Loop Gain
Unity-Gain Bandwidth
EAN Input Bias Current
Error Amplifier Output
Clamping Voltage
INPUTS (MODE AND OVI)
MODE Input-Voltage High
MODE Input-Voltage Low
MODE Pulldown Current
OVI Trip Threshold
OVI Hysteresis
OVI Input Bias Current
OVP
TH
OVI
HYS
I
OVI
V
OVI
= 1V
4
1.244
5
1.276
200
0.2
2
0.8
6
1.308
V
V
µA
V
mV
µA
A
VOLEA
f
GBW
I
B(EA)
V
CLAMP
(EA)
70
3
V
EAN
= 2V
With respect to V
CM
-0.2
905
+0.03
930
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Maxim Integrated
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4
MAX16821A/MAX16821B/
MAX16821C
Electrical Characteristics (continued)
High-Power Synchronous HBLED
Drivers with Rapid Current Pulsing
(V
CC
= 5V, V
DD
= V
CC
, T
A
= T
J
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
ENABLE INPUT (EN)
EN Input-Voltage High
EN Input Hysteresis
EN Pullup Current
THERMAL SHUTDOWN
Thermal Shutdown
Thermal-Shutdown Hysteresis
165
20
°C
°C
I
EN
13.5
EN rising
2.437
2.5
0.28
15
16.5
2.562
V
V
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Note 1:
All devices are 100% production tested at +25°C. Limits over temperature are guaranteed by design.
Note 2:
Does not include an error due to finite error amplifier gain. See the
Voltage-Error Amplifier
section.
Typical Operating Characteristics
(V
IN
= 12V, V
DD
= V
CC
= 5V, T
A
= +25°C, unless otherwise noted.)
MAX16821A toc01
9
SUPPLY CURRENT (mA)
8
7
6
5
4
3
2
1
0
100
EXTERNAL CLOCK
NO DRIVER LOAD
V
IN
= 24V
V
IN
= 12V
V
IN
= 5V
MAX16821A toc02
65
SUPPLY CURRENT (mA)
60
5.4
5.3
5.2
V
CC
(V)
5.1
5.0
4.9
4.8
4.7
V
IN
= 7V
V
IN
= 24V
V
IN
= 12V
55
50
45
40
V
IN
= 12V
C
DH/DL
= 22nF
-40
-15
10
35
60
85
TEMPERATURE (°C)
4.6
4.5
0
15 30 45 60 75 90 105 120 135 150
V
CC
LOAD CURRENT (mA)
300
500
700
900 1100 1300 1500
FREQUENCY (kHz)
DRIVER RISE TIME
vs. DRIVER LOAD CAPACITANCE
MAX16821A toc04
DRIVER FALL TIME
vs. DRIVER LOAD CAPACITANCE
MAX16821A toc05
200
180
160
140
t
R
(ns)
100
80
60
40
20
0
0
5
10
DL
15
20
DH
120
100
80
60
HIGH-SIDE DRIVER (DH) SINK
AND SOURCE CURRENT
MAX16821A toc06
C
LOAD
= 22nF
V
IN
= 12V
f
F
(ns)
40
20
0
DL
DH
25
0
5
10
15
20
25
LOAD CAPACITANCE (nF)
LOAD CAPACITANCE (nF)
100ns/div
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Maxim Integrated
│
5
MAX16821A toc03
10
SUPPLY CURRENT (IQ) vs. FREQUENCY
70
SUPPLY CURRENT vs. TEMPERATURE
5.5
V
CC
LOAD REGULATION vs. V
IN
2A/div
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