MAX16821A_09 Datasheet, PDF (14/24 Pages) Maxim Integrated Products – High-Power Synchronous HBLED Drivers with Rapid Current Pulsing

High-Power Synchronous HBLED
Drivers with Rapid Current Pulsing
Input-Referenced Buck-Boost LED Driver
The circuit in Figure 6 shows a step-up/step-down reg-
ulator. It is similar to the boost converter in Figure 5 in
that the inductor is connected to the input and the
MOSFET is essentially connected to ground. However,
rather than going from the output to ground, the LEDs
span from the output to the input. This effectively
removes the boost-only restriction of the regulator in
Figure 5, allowing the voltage across the LED to be
greater or less than the input voltage. LED current-
sensing is not ground-referenced, so a high-side cur-
rent-sense amplifier is used to measure current.
V_LED
R8
R9
C11
C10 _R7
R6
C9
C8
R5
V_CC
R4
C3
R3
ON/OFF
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
17 EAOUT
18 EAN
19 DIFF
MAX16821A
MAX16821B
MAX16821C
LX 5
BST 4
DL 3
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
V_IN
7V TO 28V
C2
L1
D1
Q1
C1
R2
C2
LED
STRING
1 TO 6
LEDS
V_LED
V_CC
RS+
RS- OUT
R1
C7
C6
C5
Figure 6. Typical Application Circuit for an Input-Referred Buck-Boost LED Driver (7V to 28V Input)
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