MAX16821BEVKIT+ Maxim Integrated Products, MAX16821BEVKIT+ Datasheet - Page 15

• Manufacturer Part Number: MAX16821BEVKIT+
• Description: KIT EVAL FOR MAX16821B
• Manufacturer: Maxim Integrated Products

Specifications of MAX16821BEVKIT+

• Current - Output / Channel: 660mA
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 28V
• Features: Dimmable
• Voltage - Input: 7 ~ 24V
• Utilized Ic / Part: MAX16821
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 7 shows the MAX16821A/MAX16821B/
MAX16821C configured as a SEPIC LED driver. While
buck topologies produce an output always lower than
the input, and boost topologies produce an output
always greater than the input, a SEPIC topology allows
the output voltage to be greater than, equal to, or less
than the input. In a SEPIC topology, the voltage across
C3 is the same as the input voltage, and L1 and L2 have
the same inductance. Therefore, when Q1 turns on (on-
time), the currents in both inductors (L1 and L2) ramp
up at the same rate. The output capacitor supports the
output voltage during this time. When Q1 turns off (off-
time), L1 current recharges C3 and combines with L2 to
Figure 7. Typical Application Circuit for a SEPIC LED Driver
V
LED
R8
R9
C9
C8
C10
R5
C7
R6
R7
______________________________________________________________________________________
17
18
19
15
16
20
21
CLP
DIFF
OVI
EAOUT
EAN
CSN
CSP
SGND
14
I.C.
22
Drivers with Rapid Current Pulsing
SEPIC LED Driver
SENSE- SENSE+
OUTV
13
R3
23
High-Power Synchronous HBLED
RT/SYNC
12
24
C2
MAX16821A
MAX16821B
MAX16821C
R4
SGND
V
EN
11
25
CC
V
C6
IN
MODE
10
26
IN
ON/OFF
C5
CLKOUT
provide current to recharge C1 and supplies the load
current. Since the voltage waveform across L1 and L2
are exactly the same, it is possible to wind both induc-
tors on the same core (a coupled inductor). Although
voltages on L1 and L2 are the same, RMS currents can
be quite different so the windings may require a differ-
ent gauge wire. Because of the dual inductors and seg-
mented energy transfer, the efficiency of a SEPIC
converter is lower than the standard buck or boost con-
figurations. As in the boost driver, the current-sense
resistor connects to ground, allowing the output voltage
of the LED driver to exceed the rated maximum voltage
of the MAX16821A/MAX16821B/MAX16821C.
V
27
9
CC
C4
SGND
V
PGND
28
8
DD
N.C.
N.C.
BST
LX
DL
DH
4
7
6
5
3
2
1
L1
7V TO 28V
Q1
R1
V
C3
IN
L2
D1
C1
R2
V
LED
LED
STRING
15