MAX16821BEVKIT+ Maxim Integrated Products, MAX16821BEVKIT+ Datasheet - Page 11

• 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

The MAX16821A/MAX16821B/MAX16821C include a
transconductance current-error amplifier with a typical
g
bility. The current-error amplifier output (CLP) is con-
nected to the inverting input of the PWM comparator.
CLP is also externally accessible to provide frequency
compensation for the inner current regulation loop
(Figure 2). Compensate CEA so the inductor current
negative slope, which becomes the positive slope to
the inverting input of the PWM comparator, is less than
the slope of the internally generated voltage ramp (see
the Compensation section). In applications without syn-
chronous rectification, the LED driver can be turned off
and on instantaneously by shorting or opening the CLP
to ground.
An internal PWM comparator sets the duty cycle by
comparing the output of the current-error amplifier to a
Figure 3. MAX16821A/MAX16821B/MAX16821C Phase Circuit
m
of 550µS and 320µA output sink and source capa-
RAMP
SHDN
CSN
CSP
CLP
CLK
IN
PWM Comparator and R-S Flip-Flop
______________________________________________________________________________________
60mV
Current-Error Amplifier
A
Drivers with Rapid Current Pulsing
V
= 34.5
High-Power Synchronous HBLED
g
m
= 550µS
PEAK-CURRENT
COMPARATOR
COMPARATOR
PWM
2V
R-S flip-flop resets and the high-side driver (DH) turns
on if MODE is connected to SGND, and DL turns on if
MODE is connected to V
flip-flop as soon as the ramp signal exceeds the CLP
voltage, thus terminating the ON cycle. See Figure 3.
The differential amplifier (DIFF) allows LED current sens-
ing (Figure 2). It provides true-differential LED current
sensing, and amplifies the sense voltage by a factor of 1
(MAX16821A), 6 (MAX16821B), and 20 (MAX16821C),
while rejecting common-mode voltage errors. The VEA
provides the difference between the differential amplifier
output (DIFF) and the desired LED current-sense volt-
age. The differential amplifier has a bandwidth of 1.7MHz
(MAX16821A), 1.6MHz (MAX16821B), and 550kHz
(MAX16821C). The difference between SENSE+ and
SENSE- is regulated to +0.6V (MAX16821A), +0.1V
(MAX16821B), or +0.03V (MAX16821C).
P-P
ramp signal. At the start of each clock cycle, an
S
R
MODE = GND
Q
Q
CC
Differential Amplifier
. The comparator sets the
BST
DH
LX
V
DL
PGND
DD
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