MAX1573ETE+ Maxim Integrated Products, MAX1573ETE+ Datasheet - Page 5

• Manufacturer Part Number: MAX1573ETE+
• Description: IC LED DRVR WHITE BCKLGT 16-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Backlight, White LEDr

Specifications of MAX1573ETE+

• Constant Current: Yes
• Topology: Linear (LDO), PWM, Step-Down (Buck), Step-Up (Boost), Switched Capacitor (Charge Pump)
• Number Of Outputs: 4
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 1MHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Voltage - Output: 5V
• Mounting Type: Surface Mount
• Package / Case: 16-TQFN Exposed Pad
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 28mA
• Internal Switch(s): Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Efficiency: -
• Lead Free Status / Rohs Status: Details

The MAX1573 is a complete charge-pump buck-boost
converter requiring only four small ceramic capacitors.
TQFN
EN1
EN2
SET
IN
13
14
15
16
P
N
PIN
UCSP
D1
C1
B1
A1
MAX1573
BRIGHTNESS
CONTROL
0.15V
0.6V
NAME
P
_______________________________________________________________________________________
C1N
C2N
C1P
C1P
IN
1x/1.5x REGULATED CHARGE PUMP
C1N
Detailed Description
GND
Transfer Capacitor 1 Negative Connection. See the Component Selection section for capacitor value.
Supply Voltage Input. IN supplies power for the IC. Bypass IN to GND with a 1µF ceramic capacitor.
Transfer Capacitor 2 Negative Connection. See the Component Selection section for capacitor value.
Transfer Capacitor 1 Positive Connection. See the Component Selection section for capacitor value.
Block Diagram
C2P C2N
LDO CURRENT
LDO CURRENT
LDO CURRENT
LDO CURRENT
White LED 1x/1.5x Charge Pump in
MINIMUM
REGULATOR
REGULATOR
REGULATOR
REGULATOR
SELECT
1.25V
OUT
LED1
LED2
LED3
LED4
The MAX1573 utilizes a proprietary 1x/1.5x fractional
charge-pump topology to drive up to four white LEDs
with regulated constant current for uniform intensity.
The MAX1573 operates with a 1MHz fixed frequency.
An external resistor (R
current, while two digital inputs control on/off and pro-
vide brightness control.
The MAX1573 operates in 1x mode until just above
dropout. Then the MAX1573 switches to 1.5x charge-
pump mode to regulate the lowest of LED1–LED4 to
150mV and maintain constant LED brightness even at
very low battery voltages. Using this topology, there is
no LED brightness change during the 1x/1.5x switchover,
which guarantees no flicker on the display. The
switchover scheme has low hysteresis, minimizing
operation in the less-efficient 1.5x mode. The 1x mode
produces almost no ripple, while the 1.5x mode regu-
lates the output voltage by controlling the rate at which
the transfer capacitors are charged. In this way, the
switching frequency remains constant for reduced input
ripple and stable noise spectrum.
The MAX1573 includes 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 output
capacitor is charged directly from the input with a DAC-
ramped current source (with no charge-pump action)
until the output voltage is near 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. In the case
of 1.5x mode, soft-start operates until the lowest of
LED1–LED4 reaches regulation. If an overload condi-
tion occurs, soft-start repeats every 2.1ms. If the output
is shorted to ground, the output current is limited by
the MAX1573 fractional-switching technique.
FUNCTION
UCSP and Thin QFN
Pin Description (continued)
SET
) programs the full-scale LED
Output Regulation
Soft-Start
5