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)
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