LTC3524EUF#PBF Linear Technology, LTC3524EUF#PBF Datasheet - Page 7

• Manufacturer Part Number: LTC3524EUF#PBF
• Description: IC TFT BIAS SUPPLY ADJ 24-QFN
• Manufacturer: Linear Technology

Specifications of LTC3524EUF#PBF

• Applications: LCD Display
• Voltage - Supply: 2.5 V ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-QFN
• Operating Supply Voltage (typ): 3.3/5V
• Number Of Segments: 8
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Package Type: QFN EP
• Pin Count: 24
• Mounting: Surface Mount
• Operating Supply Voltage (min): 2.5V
• Operating Supply Voltage (max): 6V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Lead Free Status / Rohs Status: Compliant

WHITE LED DRIVER PIN FUNCTIONS
FBN (Pin 13): Feedback Pin for the VN Charge-Pump
Output. Reference voltage is 1.0V. Connect the resistive
divider tap between V
trace area.
FBH (Pin 14): Feedback Pin for the VH Charge-Pump
Output. Reference voltage is 1.225V. Connect resistive
divider tap here with minimum trace area.
VH (Pin 15): Charge Pump Quadrupler Output. This output
can be regulated to 4X V
LED2 (Pin 18): Output for Second LED String. Connect
up to fi ve white LEDs between LED2 (anode) and GND
(cathode). For best current matching and effi ciency use
the same number of white LEDs in both strings.
LED1 (Pin 19): Output for First LED String.
VLED (Pin 20): Output of the LED Switcher. Bypass VLED
with a low ESR, ESL ceramic capacitor (X5R type) of at
least 1μF. Keep PCB trace lengths as short and wide as
possible to minimize EMI and voltage overshoot.
SW2 (Pin 21): White LED Boost Switch. Connect a 3.3-
15μH inductor between SW2 and V
of the internal NPN power switch. Connect an external
Schottky diode between SW2 and VLED. Keep PCB trace
lengths as short and wide as possible to minimize EMI
and voltage overshoot.
ELED2 (Pin 22): Enable and PWM Dimming Control Input
for the LED2 String. The LED2 string is disabled when this
pin is grounded. Digital dimming can be implemented
by driving the ELED2 pin between 0V and >1.2V at low
LCD BIAS PIN FUNCTIONS
VN
VH
=
=
1 225 1
−
.
R
6
(
V
R
⎛
⎝ ⎜
OUT
5
+
R
R
−
3
4
OUT
1
)
⎞
⎠ ⎟
OUT
+
and VN here with minimum
1 (
(
See Block Diagram
and is capable of delivering
See Block Diagram
IN
. This is the collector
)
)
up to 2mA to a load. VH should be bypassed to GND with
a 0.47μF X5R type ceramic capacitor. Connect V2x to
V
than 2X V
CH
Positive Node. The charge pump quadrupler (4X) fl ying
capacitor is connected between CH
on CH
50% duty cycle while the charge pump is operating. Use
a 0.1μF X5R type ceramic capacitor for best results.
CH
pacitor Negative Node. The voltage on CH
between GND and V2x at an approximate 50% duty cycle
while the charge pump is operating. Use a 0.1μF X5R type
ceramic capacitor for best results.
frequency (ie., 500Hz). Driving ELCD, ELED1, and ELED2
low initiates shutdown mode which disables all IC func-
tions and reduces quiescent current from the battery to
less than 2μA.
PROG (Pin 23): A single resistor (RPROG) between
PROG and GND sets the current in the LED strings. LED
current in mA is programmed by:
A 100K resistor programs 20mA in each string. Analog
dimming can be implemented by connecting a second
resistor between PROG and a control voltage.
ELED1 (Pin 24): Enable and Pulse Dimming Control Input
for the LED1 String. For applications with fi ve or fewer
LEDs, better effi ciency is achieved by operating a single
LED string. For example, ELED1 = 1, ELED2 = 0, LED2 left
open circuit and the LED string connected to LED1.
OUT
ILED
+
–
(Pin 16): Charge Pump Quadrupler Flying Capacitor
(Pin 17): Charge Pump Quadrupler (4X) Flying Ca-
+
for applications requiring a regulated voltage less
will alternate between V2x and VH at an approximate
1
=
OUT
ILED
.
2
=
⎛
⎜
⎝
2 10
R
×
PROG
6
⎞
⎟
⎠
mA
+
and CH
LTC3524
–
–
will alternate
. The voltage
7
3524f