MAX158 Maxim, MAX158 Datasheet - Page 5

• Manufacturer Part Number: MAX158
• Description: High-Efficiency / 26V Step-Up Converter for White LED Main and Subdisplay Backlighting
• Manufacturer: Maxim

(See the Typical Applications Circuit, V
V
CTRL
QFN
10
11
12
EP
1
2
3
4
5
6
7
8
9
for White LED Main and Subdisplay Backlighting
= 1.5V, 4 LEDs, T
PIN
UCSP
C4
D4
D3
D2
D1
C1
A1
A2
A3
A4
B4
B1
—
_______________________________________________________________________________________
SWITCHING WAVEFORMS
NAME
COMP
PGND
A
OUT2
OUT1
CTRL
GND
EN1
EN2
V+
CS
VP
LX
EP
= +25°C, unless otherwise noted.)
High-Efficiency, 26V Step-Up Converter
500ns/div
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
stabilizes the converter and controls soft-start. C
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
current. The voltage at CS regulates to V
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
V
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.
OUT1
V+
drops below 25V, then the IC reenters soft-start. Connect a 0.1µF capacitor from OUT1 to
= V
MAX1582 toc07
VP
= 3.6V, I
Typical Operating Characteristics (continued)
V
10mV/div
V
100mV/div
V
10V/div
IN
OUT
LX
LED
= 15mA, L1 = 22µH, C
OUT1
is greater than 27V, the internal N-channel MOSFET turns off until
CTRL
FUNCTION
/ 10 or +0.162V, whichever is lower.
COMP
OUT1
DIRECT-PWM DIMMING
SENSE
COMP
discharges to GND when in shutdown.
= 0.1µF, C
) from COMP to GND. C
) from CS to GND to set the LED bias
50µs/div
V
IN = 3.8V Li+ BATTERY
COMP
Pin Description
= 0.022µF, R
MAX1582 toc08
V
32kHz
1V/div
0V
V
50mV/div
I
50mA/div
0mA
V
5V/div
0V
IN
CTRL
IN
OUT
COMP
SENSE
= 7.5Ω,
5