MAX16801A Datasheet, PDF (6/15 Pages) Maxim Integrated Products – Off-Line and DC-DC PWM Controllers for High-Brightness LED Drivers

Off-Line and DC-DC PWM Controllers for
High-Brightness LED Drivers
Typical Operating Characteristics (continued)
(V_UVLO/EN = +1.4V, V_FB = +1V, COMP = unconnected, V_CS = 0V, T_A = +25°C, unless otherwise noted.)
NDRV OUTPUT IMPEDANCE
vs. TEMPERATURE
5.0
4.8
V_IN = 24V
SOURCING 20mA
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
-40 -20 0
20 40 60 80
TEMPERATURE (°C)
ERROR-AMPLIFIER OPEN-LOOP GAIN
AND PHASE vs. FREQUENCY
120
50 ^{MAX16801 toc20}
100
30
80
10
60
GAIN
-10
40
-30
20
-50
0
PHASE
-70
-20
-90
-40
-110
-60
-130
-80
-150
-100
-170
0.1 1 10 100 1k 10k 100k 1M 10M 100M
FREQUENCY (Hz)
Pin Description
PIN
NAME
FUNCTION
1
UVLO/EN
Externally Programmable Undervoltage Lockout. UVLO programs the input start voltage. Connect
UVLO to GND to disable the device.
2
DIM/FB
Low-Frequency PWM Dimming Input/Error-Amplifier Inverting Input
3
COMP
Error-Amplifier Output. Connect the compensation components between DIM/FB and COMP in high-
accuracy LED current regulation.
4
CS
Current-Sense Connection for Current Regulation. Connect to high side of sense resistor. An RC filter
may be necessary to eliminate leading-edge spikes.
5
GND
Power-Supply Ground
6
NDRV
External n-Channel MOSFET Gate Connection
7
VCC
Gate-Drive Supply. Internally regulated down from IN. Decouple with a 10nF or larger capacitor to GND.
IC Supply. Decouple with a 10nF or larger capacitor to GND. For bootstrapped operation (MAX16801),
8
IN
connect a startup resistor from the input supply line to IN. Connect the bias winding supply to this point
(see Figure 5). For the MAX16802, connect IN directly to a +10.8V to +24V supply.
Detailed Description
The MAX16801/MAX16802 family of devices is intend-
ed for constant current drive of high-brightness (HB)
LEDs used in general lighting and display applications.
They are specifically designed for use in isolated and
non-isolated circuit topologies such as buck, boost, fly-
back, and SEPIC, operating in continuous or discontin-
uous mode. Current mode control is implemented with
an internally trimmed, fixed 262kHz switching frequen-
cy. A bootstrap UVLO with a large hysteresis (11.9V),
very low startup current, and low operating current,
result in an efficient universal-input LED driver. In addi-
tion to the internal bootstrap UVLO, these devices also
offer programmable input startup voltage programmed
through the UVLO/EN pin. The MAX16801 is well suited
for universal AC input (rectified 85VAC to 265VAC) dri-
vers. The MAX16802 is well suited for low input voltage
(10.8VDC to 24VDC) applications.
The MAX16801/MAX16802 regulate the LED current by
monitoring current through the external MOSFET cycle
by cycle.
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