AAT2869 Advanced Analogic Technologies, Inc., AAT2869 Datasheet - Page 17

• Manufacturer Part Number: AAT2869
• Description: Fade-in/fade-out 4 Channel Backlight Driver With Dual Ldos
• Manufacturer: Advanced Analogic Technologies, Inc.

For most applications, ceramic capacitors with X5R tem-
perature characteristic are preferred for AAT2869 appli-
cation. These capacitors have good capacitor tolerance
over wide temperature (X5R: ±15% over -55°C to
+85°C). Capacitors with Y5V or Z5U temperature char-
acteristic are generally not recommended for AAT2869.
They have wide capacitance tolerance over special tem-
perature (Y5V: +22%, -82% over -30°C to +85°C, Z5U:
+22%, -56% over +10°C to +85°C).
Careful selection of the four external capacitors C
C
time, output ripple and transient performance. Optimum
performance will be obtained when low ESR (<100mΩ)
ceramic capacitors are used. In general, low ESR may be
defined as less than 100mΩ. A capacitor value of 1uF for
all four capacitors is a good starting point when choosing
capacitors. If the LED current sinks are only programmed
for light current levels, then the capacitor size may be
decreased.
2869.2010.01.1.0
SystemPower
Manufacturer
2
, C
OUT
Murata
TDK
is important because they will affect turn on
TM
GRM188R61C105KA93
GRM188R61A225KE34
GRM185R60J105KE21
C1608X5R1C105K
2.7~5.5V
C1608X5R0J225K
Part Number
V
AS
IN
2
Cwire
Figure 3: Higher Current, Single LED Application.
2.2μF
Fade-In/Fade-Out 4 Channel Backlight Driver with Dual LDOs
Table 6: AAT2869 Recommended Capacitors.
C
1μF
IN
1μF
C
C1
F
Value (μF)
FCAP
EN/SET
w w w . a n a l o g i c t e c h . c o m
C1+
C1-
INLDO
IN
GND
2.2
2.2
AAT2869
1
1
1
IN
, C
OUTCP
1
,
AGND
LDOA
LDOB
Voltage
C2+
C2-
D1
D2
D3
D4
6.3
6.3
16
10
16
Additional Applications
The current sinks of the AAT2869 can be combined to
drive higher current levels through a single LED. As an
example, Figure 3 shows the AAT2869 driving a single
white LED with up to 124mA by connecting D1-D4
together to the LED cathode.
Printed Circuit Board
Layout Recommendations
When designing a PCB for the AAT2869, the key require-
ments are:
1. Place the flying capacitors C1 and C2 as close to the
2. Place the input and output decoupling capacitors as
3. Connect the exposed pad to GND plane for optimal
chip as possible; otherwise 1.5x mode performance
will be compromised.
close to the chip as possible to reduce switching
noise and output ripple.
power dissipation.
C2
1μF
C
1μF
Temp. Co.
OUT
C
2.2μF
X5R
X5R
X5R
X5R
X5R
LDOB
D1
LDOB
Up to
124mA
ESR (mΩ) at 1MHz
PRODUCT DATASHEET
C
2.2μF
LDOA
LDOA
5.5
3.3
18
16
12
AAT2869
Case
0603
0603
0603
0603
0603
17