MAX1582 Datasheet, PDF (5/10 Pages) Maxim Integrated Products – High-Efficiency, 26V Step-Up Converter for White LED Main and Subdisplay Backlighting

High-Efficiency, 26V Step-Up Converter
for White LED Main and Subdisplay Backlighting
Typical Operating Characteristics (continued)
(See the Typical Applications Circuit, V_V+ = V_VP = 3.6V, I_LED = 15mA, L1 = 22µH, C_OUT1 = 0.1µF, C_COMP = 0.022µF, R_SENSE = 7.5Ω,
V_CTRL = 1.5V, 4 LEDs, T_A = +25°C, unless otherwise noted.)
SWITCHING WAVEFORMS
MAX1582 toc07
V_IN
10mV/div
V_OUT
100mV/div
500ns/div
V_LX
10V/div
DIRECT-PWM DIMMING
MAX1582 toc08
V_CTRL
32kHz
1V/div
0V
V_IN
50mV/div
I_IN
50mA/div
0mA
V_{IN = 3.8V Li+ BATTERY}
50µs/div
V_OUT
5V/div
0V
PIN
QFN UCSP
1
A1
2
A2
3
A3
4
A4
5
B4
6
C4
7
D4
8
D3
9
D2
10
D1
11
C1
12
B1
EP
—
Pin Description
NAME
FUNCTION
V+
VP
CTRL
COMP
GND
EN1
EN2
CS
OUT2
OUT1
LX
PGND
EP
Input Voltage Supply. Input voltage range is 2.6V to 5.5V. Connect a 2.2µF capacitor from V+ to
PGND.
High-Current Input Supply. Connect to V+.
Brightness Control Input. LED brightness is controlled by the voltage applied to CTRL. Varying the
voltage from 0 to +1.62V adjusts the brightness from dim to bright, respectively. Any voltage
above +1.62V does not increase brightness.
Compensation Input. Connect a 0.022µF capacitor (C_COMP) from COMP to GND. C_COMP
stabilizes the converter and controls soft-start. C_COMP discharges to GND when in shutdown.
Ground. Connect to PGND at a single point near the IC.
Enable 1 Input. Drive EN1 high to enable the main-display LEDs. Pull EN1 low to turn off the main-
display LEDs. Pull both EN1 and EN2 low to place the IC in low-current shutdown mode.
Enable 2. Drive EN2 high to enable the subdisplay LEDs. Pull EN2 low to turn off the subdisplay
LEDs. Pull both EN1 and EN2 low to place the IC in low-current shutdown mode.
Current-Sense Feedback Input. Connect a resistor (R_SENSE) from CS to GND to set the LED bias
current. The voltage at CS regulates to V_CTRL / 10 or +0.162V, whichever is lower.
Display Switch Output. OUT2 is internally connected to CS when only the main display is lit. OUT2
is internally connected to OUT1 when only the subdisplay is lit. OUT2 is high impedance when
both displays are lit and when the IC is shut down.
Overvoltage Sense. When V_OUT1 is greater than 27V, the internal N-channel MOSFET turns off until
V_OUT1 drops below 25V, then the IC reenters soft-start. Connect a 0.1µF capacitor from OUT1 to
PGND.
Inductor Connection. During shutdown, this pin is high impedance.
Power Ground. Connect to GND at a single point near the IC.
Exposed Paddle. Connect directly to GND and PGND under the IC.
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