Rainbow Electronics MAX8848Z - Manual

_______________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
High-Performance Negative Charge Pump
for 7 White LEDs in 3mm x 3mm Thin QFN MAX8848Y/MAX8848Z
19-5233; Rev 0; 4/10
Typical Operating Circuit
General Description
The MAX8848Y/MAX8848Z negative charge pumps
drive up to 7 white LEDs with regulated constant current
for display backlight applications. By utilizing an invert-
ing charge pump and extremely low-dropout adaptive
current regulators, these ICs achieve very high efficiency
over the full 1-cell Li+ battery voltage range even with
large LED forward voltage mismatch. The 1MHz fixed-
frequency switching allows for tiny external components.
The regulation scheme is optimized to ensure low EMI
and low input ripple. The MAX8848Y/MAX8848Z include
thermal shutdown, open- and short-circuit protection.
The MAX8848Y/MAX8848Z support independent LED
on/off and dimming control. The MAX8848Y dimming
ranges are pseudo-logarithmic from 24mA to 0.1mA and
off in 32 steps. All devices include a temperature derat-
ing function to safely allow bright 24mA full-scale output
current while automatically reducing current gradually
to protect LEDs at high ambient temperatures above
+60NC.
The MAX8848Y/MAX8848Z are available in 16-pin,
3mm x 3mm thin QFN packages.
Applications
White LED Backlighting
Cellular Phones
PDAs, Digital Cameras, and Camcorders
Features
S
Negative 1x/1.5x Charge Pump
S
Adaptive Current Regulators
S
Independent Voltage Supply for Each LED
S
24mA to 0.1mA Serial-Pulse Dimming (MAX8848Y)
S
24mA to 0mA PWM Dimming (MAX8848Z)
S
2% (max) LED Current Accuracy, 1% (typ) Matching
S
Low 120µA Quiescent Current
S
Low 0.4µA Shutdown Current
S
Inrush Current Limit
S
Temperature Derating Function
S
16-Pin, 3mm x 3mm Thin QFN Packages
Ordering Information
Note: All devices are specified over the -40°C to +85°C
extended temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
EVALUATION KIT
AVAILABLE
1 µF
INPUT
2.7V TO 5.5V
IN
NEG
LED1
D1
D2
D3
D4
D5
D6
D7
LED2
LED3
LED4
LED5
LED6
LED7
EP
C1P C1N C2P C2N
GND
ENA
(ENB)
<CPWM>
LED ENABLE
AND
DIMMING
CONTROL
1 µF
0.22 µF
NOTE: ( ) FOR MAX8848Y, < > FOR MAX8848Z
1 µF
1 µF
MAX8848Y
MAX8848Z
PART DIMMING PIN-PACKAGE
TOP
MARK
MAX8848YETE+T
Serial pulse/
PWM
16 Thin QFN-EP* AHQ
MAX8848ZETE+T PWM 16 Thin QFN-EP* AHP