MAX16833EVKIT+ Maxim Integrated Products, MAX16833EVKIT+ Datasheet - Page 12

• Manufacturer Part Number: MAX16833EVKIT+
• Description: KIT EVAL FOR MAX16833 LED DRIVER
• Manufacturer: Maxim Integrated Products

Specifications of MAX16833EVKIT+

• Current - Output / Channel: 1A
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 3 ~ 36 V
• Features: Analog Brightness control
• Voltage - Input: 5 ~ 18 V
• Utilized Ic / Part: MAX16833A/B
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

High-Voltage HB LED Drivers with
Integrated High-Side Current Sense
The ICs offer an analog dimming control input (ICTRL).
The voltage at ICTRL sets the LED current level when
V
from zero with the voltage on ICTRL. For V
an internal reference sets the LED current. The maximum
withstand voltage of this input is 5.5V.
The ICs feature a 7V low-side linear regulator (V
V
ing capability of up to 50mA. Use a 1FF (min) low-ESR
ceramic capacitor from V
tion. The V
age falls below 7V. The dropout voltage for this regulator
at 50mA is 0.2V. This means that for an input voltage of
5V, the V
the V
V
The differential voltage from ISENSE+ to ISENSE- is fed
to an internal current-sense amplifier. This amplified sig-
nal is then connected to the negative input of the trans-
conductance error amplifier. The voltage-gain factor of
this amplifier is 6.15.
The offset voltage for this amplifier is P 1mV.
The ICs have a built-in transconductance amplifier used
to amplify the error signal inside the feedback loop.
When the dimming signal is low, COMP is disconnected
from the output of the error amplifier and DIMOUT goes
high. When the dimming signal is high, the output of
the error amplifier is connected to COMP and DIMOUT
goes low. This enables the compensation capacitor to
hold the charge when the dimming signal has turned off
the internal switching MOSFET gate drive. To maintain
the charge on the compensation capacitor C
in the Typical Operating Circuits), the capacitor should
be a low-leakage ceramic type. When the internal dim-
ming signal is enabled, the voltage on the compensation
capacitor forces the converter into steady state almost
instantaneously.
12
ICTRL
CC
IN
Internal Transconductance Error Amplifier
is always less than 7V.
_____________________________________________________________________________________
powers up the switching MOSFET driver with sourc-
CC
< 1.2V. The LED current can be linearly adjusted
regulator is 100mA (typ). Connect V
CC
LED Current-Sense Inputs (ISENSE±)
CC
voltage is 4.8V. The short-circuit current on
regulator goes below 7V if the input volt-
Low-Side Linear Regulator (V
Analog Dimming (ICTRL)
CC
to PGND for stable opera-
ICTRL
CC
COMP
> 1.4V,
to IN if
CC
CC
(C4
).
)
The internal oscillators of the ICs are programmable from
100kHz to 1MHz using a single resistor at RT/SYNC.
Use the following formula to calculate the switching fre-
quency:
where R
Synchronize the oscillator with an external clock by
AC-coupling the external clock to the RT/SYNC input.
For f
for the AC-coupling should satisfy the following relation:
where R
268nF.
The pulse width for the synchronization pulse should
satisfy the following relations:
where t
t
the free-running oscillator time period, and V
chronization pulse-voltage level.
Ensure that the external clock signal frequency is at least
1.1 x f
by R
proper synchronization of a frequency up to 250kHz. A
rising external clock edge (sync) is interpreted as a syn-
chronization input. If the sync signal is lost, the internal
oscillator takes control of the switching rate returning the
switching frequency to that set by R
output regulation even with intermittent sync signals.
CLK
f
f
OSC
OSC
OSC
RT
is the synchronization clock time period, t
C
(kHz)
(kHz)
OSC,
t
. A typical pulse width of 200ns can be used for
SYNC
t
PW
RT
CLK
RT
PW
between 200kHz and 1MHz, the capacitor used
is the resistor from RT/SYNC to SGND.
is in kω. For f
is the synchronization source pulse width,
=
=
3.4V
where f
<
≤
6929 k
7350 k
R
R
0.5
V
9.8624 10
RT
RT
S
<
(k )
Internal Oscillator (RT/SYNC)
(k )
( )



( )
0.8 -
R
and
Ω
OSC
Ω
Ω
Ω
RT
×
for the MAX16833C MAX16833D
for the MAX16833 MAX16833B
t
t
is the oscillator frequency set
OSC
CLK
t
PW
t
-6
CLK
PW
−
V
below 200GHz, C
0.144 10
S
< 





1-
+
V
1.05 t
×
S
RT
<
t
. This maintains
OSC
5V
-9
×
farads
CLK
S
is the syn-



SYNC
OSC
is
≤