MAX1577ZETA-T Maxim Integrated Products, MAX1577ZETA-T Datasheet - Page 8

• Manufacturer Part Number: MAX1577ZETA-T
• Description: Charge Pumps
• Manufacturer: Maxim Integrated Products

Specifications of MAX1577ZETA-T

• Function: Step Up, Step Down
• Output Voltage: 5.1 V
• Output Current: 1200 mA
• Maximum Operating Temperature: + 85 C
• Package / Case: TDFN-8 EP
• Minimum Operating Temperature: - 40 C
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

When V
MAX1577Z are in 1x LDO mode and regulate the cur-
rent through R
approaches dropout, the 2x charge pump starts boosting
the output to maintain the regulation current. When V
rises enough above V
charge pump stops and the MAX1577Y/MAX1577Z
switch back to the more efficient 1x LDO mode.
The MAX1577Y/MAX1577Z include soft-start circuitry to
limit inrush current at turn-on. When starting up with an
output voltage that is not near the input voltage, the out-
put capacitor is charged directly from the input with a
ramped current source (with no charge-pump action)
until the output voltage approaches the input voltage. If
current-mode or voltage-mode regulation is met, soft-
1.2A White LED Regulating Charge Pump for
Camera Flashes and Movie Lights
Figure 4. Flash and Backlighting with the MAX1577Y
8
_______________________________________________________________________________________
5.1V OR 100% CURRENT,
4.6V OR 33% CURRENT,
3.4V OR 20% CURRENT,
*1µF FOR LESS THAN 600mA OUTPUT.
IN
AND SHUTDOWN
is greater than V
2.7V TO 5.5V
4.7µF
1x LDO to 2x Mode Switchover
CS
C
IN
. As V
OUT
Detailed Description
to maintain LDO regulation, the
IN
IN
GND
EN1
EN2
CP
decreases and the LDO
MAX1577Y
2.2µF*
OUT
C1
, the MAX1577Y/
CN
OUT
CS
V
100 OR 60mV)
5.3V OVP
Soft-Start
OUT
- (300 OR
C
10µF
IN
UP TO 1.2A
IN
CAMERA-FLASH
MOVIE LIGHT
R
CS
start is terminated and normal operation begins in 1x
mode. Otherwise, after 500µs, the 2x charge-pump soft-
start operates until the voltage across the sense resistor
reaches the current regulation threshold, the output volt-
age is in regulation, or 500µs has elapsed, whichever
occurs first. If the output is shorted to ground, soft-start
is repeated until the output exceeds 2.3V.
The MAX1577Y/MAX1577Z use two inputs (EN1 and
EN2) to select between three brightness levels and low-
power shutdown mode (see Table 1). By regulating the
voltage across the current-sense resistor (V
one of three levels, the MAX1577Y/MAX1577Z control the
output current, thus providing the three-level dimming. In
shutdown mode, the IC is turned off, reducing the supply
current to 0.01µA (typ). When the MAX1577Y/MAX1577Z
are shut down, C1 is discharged and the output is pulled
to GND through an internal 5kΩ resistor.
5.1V, 4.6V, OR 3.4V
MAIN DISPLAY
BACKLIGHT
Dimming and Shutdown
SUBDISPLAY
BACKLIGHT
RGB DRIVER
ASIC
OUT
- V
CS
) to