MAX16810 Maxim Integrated Products, MAX16810 Datasheet - Page 15

• Manufacturer Part Number: MAX16810
• Description: (MAX16809 / MAX16810) Integrated 16-Channel LED Drivers
• Manufacturer: Maxim Integrated Products

The oscillator frequency is then:
REF is a 5V reference output that can source 20mA.
Bypass REF to AGND with a 0.1µF capacitor.
The MAX16809/MAX16810 include a fast current-limit
comparator to terminate the ON cycle during an over-
load or a fault condition. The current-sense resistor,
R
MOSFET and AGND, sets the current limit. The CS
input has a voltage trip level (V
lowing equation to calculate R
Figure 2. Buck-Boost (SEPIC) Operation
3V TO 5.5V
CS
V
IN
CLOCK INPUT
, connected between the source of the external
EXTERNAL
DIM INPUT
EXTERNAL
R
C
SET
C
BYP
IN
V
V+
PGND
DIN
LE
CLK
DOUT
OE
SET
OUT CS AGND
CC
L1
Switch-Mode Boost and SEPIC Controller
C
REF
______________________________________________________________________________________
f
OSC
Integrated 16-Channel LED Drivers with
REF
MAX16809
MAX16810
=
Q1
R
R
T
CS
(
COMP
C
t
1
C
CS
L2
+
1
CS
C
RTCT
C1
:
Reference Output
t
) of 0.3V. Use the fol-
D
C
C2
C
OUT10
OUT11
OUT12
OUT13
OUT14
OUT15
D
)
T
OUT0
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
OUT8
OUT9
R
C
C1
FB
OUT
Current Limit
R1
R2
V
OUT
I
When the voltage produced by this current (through the
current-sense resistor) exceeds the current-limit com-
parator 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.
Figure 2 shows a buck-boost application circuit using
the MAX16809/MAX16810 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
V
P-P
OUT
is the peak current that flows through the MOSFET.
can be below or above V
Buck-Boost (SEPIC) Operation
R
CS
=
I
V
P P
CS
−
IN
.
15