MAX16821A Datasheet, PDF (13/25 Pages) Maxim Integrated Products – High-Power Synchronous HBLED Drivers with Rapid Current Pulsing

High-Power Synchronous HBLED
Drivers with Rapid Current Pulsing
Applications Information
Boost LED Driver
Figure 5 shows the MAX16821A/MAX16821B/MAX16821C
configured as a synchronous boost converter with
MODE connected to V_CC. During the on-time, the input
voltage charges the inductor. During the off-time, the
inductor discharges to the output. The output voltage
cannot go below the input voltage in this configuration.
Resistor R1 senses the inductor current and resistor R2
senses the LED current. The outer LED current regula-
tion loop programs the average current in the inductor,
thus achieving tight LED current regulation.
V_LED
R9
R10
C11
C10 _R8
R7
C9
C8
R5
V_CC
R4
C3
R3
ON/OFF
V_IN
7V TO 28V
14
I.C.
15 OVI
13
12
11
OUTV RT/SYNC EN
10
MODE
9
CLKOUT
8
SGND
N.C. 7
16 CLP
DH 6
L1
Q2
17 EAOUT
18 EAN
19 DIFF
MAX16821A
MAX16821B
MAX16821C
LX 5
C4
BST 4
R5
DL 3
C2
V_LED
Q1
C1
LED
STRING
R2
20 CSN
N.C. 2
21 CSP
SGND SENSE- SENSE+ SGND
IN
22
23
24
25
26
V_IN
PGND 1
V_CC
V_DD
27
28
D1
R1
C7
C6
C5
Figure 5. Synchronous Boost LED Driver (Output Voltage Not to Exceed 28V)
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