MAX1575ETE/V+T Maxim Integrated, MAX1575ETE/V+T Datasheet - Page 5

• Manufacturer Part Number: MAX1575ETE/V+T
• Description: LED Lighting Drivers White LED 1x/1.5x Charge Pump for Main and Sub-Displays
• Manufacturer: Maxim Integrated

Specifications of MAX1575ETE/V+T

• Input Voltage: 2.7 V to 5.5 V
• Maximum Supply Current: 2 mA
• Power Dissipation: 1349 mW

The MAX1575 charge pump drives up to four white
LEDs in the main display and up to two white LEDs in
the sub-display with regulated constant current for
uniform intensity. By utilizing adaptive 1x/1.5x charge-
pump modes and very-low-dropout current regulators, it
achieves high efficiency over the 1-cell lithium-battery
input voltage range. 1MHz fixed-frequency switching
allows for tiny external components and low input ripple.
When V
1x mode and V
rent regulators regulate the LED current. As V
V
100mV and the MAX1575 starts switching in 1.5x mode.
LED_
PIN
10
11
12
13
14
15
16
—
1
2
3
4
5
6
7
8
9
eventually falls below the switchover threshold of
IN
is higher than V
NAME
LED6
LED5
LED4
LED3
LED2
LED1
ENM
GND
OUT
C1N
C2N
C2P
ENS
C1P
SET
EP
IN
OUT
_______________________________________________________________________________________
Transfer-Capacitor 2 Positive Connection. Connect a 1µF ceramic capacitor from C2P to C2N.
Output. Connect a 1µF ceramic capacitor from OUT to GND. Connect OUT to the anodes of all the LEDs.
OUT is internally pulled down with 5kΩ during shutdown.
Current-Set Input. Connect a resistor (R
234 × 0.6V / R
Enable and Dimming Control for LED5 and LED6 (Sub-Display). The first time ENS goes high (50µs min),
LED5 and LED6 turn on at 100% brightness. P ul si ng E N S l ow d i m s the LE D s i n m ul ti p l e step s. If ENS is held
low for more than 2ms (typ), LED5 and LED6 turn off. When ENM and ENS are both held low for more than
2ms (typ), the IC goes into shutdown mode. See Figure 1.
E nab l e and D i m m i ng C ontr ol for LE D 1–LE D 4 ( M ai n D i sp l ay) . The fi r st ti m e E N M g oes hi g h ( 50µs m i n) ,
LE D 1–LE D 4 tur n on at 100% b r i g htness. P ul si ng E N M l ow d i m s the LE D s i n m ul ti p l e step s. If E N M i s hel d l ow for
m or e than 2m s ( typ ) , LE D 1–LE D 4 tur n off. W hen E N M and E N S ar e b oth hel d l ow for m or e than 2m s ( typ ) , the IC
g oes i nto shutd ow n m od e. S ee Fi g ur e 1.
Sub-Display LEDs Cathode Connection. Current flowing into LED_ is described in the ENS and SET
descriptions above. The charge pump regulates the lowest-enabled LED_ voltage to 180mV. Connect LED_
to IN if the LED is not populated. LED_ is high impedance during shutdown.
Main-Display LEDs Cathode Connection. Current flowing into LED_ is described in the ENM and SET
descriptions above. The charge pump regulates the lowest-enabled LED_ voltage to 180mV. Connect LED_
to IN if the LED is not populated. LED_ is high impedance during shutdown.
Ground. Connect GND as close as possible to system ground and to the ground of the input bypass
capacitor.
Transfer-Capacitor 1 Negative Connection. Connect a 1µF ceramic capacitor from C1P to C1N.
Supply Voltage Input. Connect a 1µF ceramic capacitor from IN to GND. The input voltage range is 2.7V to
5.5V. IN is high impedance during shutdown.
Transfer-Capacitor 2 Negative Connection. Connect a 1µF ceramic capacitor from C2P to C2N.
Transfer-Capacitor 1 Positive Connection. Connect a 1µF ceramic capacitor from C1P to C1N.
Exposed Paddle. Connect the exposed paddle to GND.
is pulled up to V
Detailed Description
OUT
1x to 1.5x Switchover
, the MAX1575 operates in
SET
. SET is internally biased to 0.6V. SET is high impedance during shutdown.
IN
White LED 1x/1.5x Charge Pump
. The internal cur-
IN
drops,
for Main and Sub-Displays
SET
) from SET to GND to set the maximum LED current. I
When the input voltage rises above V
the MAX1575 switches back to 1x mode.
The MAX1575 includes soft-start circuitry to limit inrush
current at turn-on. When starting up, the output capacitor
is charged directly from the input with a ramped current
source (with no charge-pump action) until the output volt-
age approaches the input voltage. Once this occurs, the
charge pump determines if 1x or 1.5x mode is required.
In the case of 1x mode, the soft-start is terminated and
normal operation begins. During the soft-start time, the
output current is set to 5% of the maximum set by R
In the case of 1.5x mode, soft-start operates until the low-
est of LED1–LED6 reaches regulation. If an overload con-
dition occurs, soft-start repeats every 2ms. If the output is
shorted to ground (or <1.25V), the part reverts to soft-
start and the ramped current source.
FUNCTION
Pin Description
OUT
by about 50mV,
LED(MAX)
Soft-Start
=
SET
5
.