Data Sheets - Skyworks Solutions, Inc.

DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
General Description
Features
The AAT3121 is a low noise, constant frequency charge
pump DC/DC converter that uses fractional (1.5X) conversion to increase efficiency in white LED applications.
With input voltages ranging from 2.7V to 5.5V, the
device can produce an output current of up to 120mA. A
low external parts count (two 1µF flying capacitors and
two small bypass capacitors at VIN and OUT) makes the
AAT3121 ideally suited for small battery-powered applications.
•VIN Range: 2.7V to 5.5V
• <1µA of Shutdown
• Only Four External Components
• Programmable LED Brightness
• Low Noise Constant Frequency Operation
• 33% Less Input Current Than Doubler Charge Pump
• Small Application Circuit
• Regulated Output Current
• Automatic Soft Start
• No Inductors
• TSOPJW-12 Package
• -40°C to +85°C Temperature Range
Skyworks' Simple Serial Control™ (S2Cwire™) interface
is used to enable, disable, and set the LED drive current
with a 32-level logarithmic scale LED brightness control.
The AAT3121 has a thermal management system to protect the device in the event of a short-circuit condition
on any of the output pins. Built-in soft-start circuitry
prevents excessive inrush current during start-up. High
switching frequency enables the use of small external
capacitors. A low shutdown current feature disconnects
the load from VIN and reduces quiescent current to less
than 1µA. The AAT3121 provides a single current source
output that can be used to drive up to six LEDs at 20mA
each.
Applications
• Programmable Current Source
• White LED Backlighting
The AAT3121 is available in a Pb-free TSOPJW-12 package and is rated over the -40°C to +85°C temperature
range.
Typical Application
VIN
C1+
C1
1µF
AAT3121
VOUT
VBATTERY
CIN
1µF
C1C2+
COUT
1µF
C2
1µF
C2-
EN/SET
EN/SET
GND
D
D1
D2
D3
D4
D5
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012
D6
1
DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Pin Descriptions
Pin #
Symbol
1
2
3
4
5, 6, 7, 8
C2+
OUT
C1C1+
D
9
EN/SET
10
11
12
IN
GND
C2-
Function
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-.
Charge pump output. Requires 1µF bypass capacitor to ground.
Flying capacitor 1 negative terminal.
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-.
Output current source with drive capability up to 120mA.
Input control pin. Serial data interface that controls the level of output current. See the Application
Information section of this datasheet for more details. This pin should not be left floating.
Input power supply. Requires 1µF bypass capacitor to ground.
Ground.
Flying capacitor 2 negative terminal.
Pin Configuration
TSOPJW-12
C2+
OUT
C1C1+
D
D
2
1
12
2
11
3
10
4
9
5
8
6
7
C2GND
IN
EN/SET
D
D
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012
DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Absolute Maximum Ratings1
Symbol
VIN
VOUT
VEN/SET
VEN/SET(MAX)
IOUT2
TJ
Description
Input Voltage
Charge Pump Output
EN/SET to GND Voltage
Maximum EN/SET to Input Voltage
Maximum DC Output Current
Operating Junction Temperature Range
Value
Units
-0.3 to 6
-0.3 to 6
-0.3 to 6
0.3
150
-40 to 150
V
V
V
V
mA
°C
Value
Units
160
625
°C/W
mW
Thermal Information3
Symbol
qJA
PD
Description
Thermal Resistance
Power Dissipation (TA = 25°C)4
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Derate 6.25mW/°C above 25°C.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012
3
DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Electrical Characteristics1
VIN = 3.5V, CIN = COUT = C1 = C2 = 1.0µF; TA = -40°C to +85°C. Unless otherwise noted, typical values are TA = 25°C.
Symbol
Description
Input Power Supply
VIN
Operation Range
ICC
Operating Current
ISHDN
Shutdown Current
IDX(MAX)
Maximum Output Current
Charge Pump
TSS
Soft-Start Time
FCLK
Clock Frequency
h
Charge Pump Efficiency
EN/SET
VEN(L)
Enable Threshold Low
VEN(H)
Enable Threshold High
TLO
EN/SET Low Time
THI
Minimum EN/SET High Time
TOFF
EN/SET Off Timeout
Input Current
EN/SET Input Leakage
Conditions
Min
Typ
2.7
3.0 ≤ VIN ≤ 5.5, Active, No Load Current
EN = 0
VIN = 3.5V; Code = 32
1.8
108
Units
5.5
3.5
1.0
132
V
mA
µA
mA
200
1000
93
VIN = 3.5V, IOUT = 40mA
VIN = 2.7V to 5.5V
VIN = 2.7V to 5.5V
120
Max
µs
kHz
%
0.5
1.4
0.3
75
50
-1.0
500
1.0
V
V
µs
ns
µs
µA
1. The AAT3121 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012
DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = COUT = C1 = C2 = 1µF, TA = 25°C.
VIH and VIL vs. VIN
IDIODE vs. VIN
(4x20mA)
90
VDIODE = 3.3V
85
VDIODE = 3.4V
IDIODE (mA)
80
0.850
VDIODE = 3.5V
VDIODE = 3.6V
0.825
0.800
75
0.775
70
0.750
65
0.725
60
0.700
55
0.675
50
0.650
45
0.625
40
0.600
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
VIH
VIL
2.5
3.0
Input Voltage (V)
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Turn-On to Full-Scale Charge Pump
Turn-On to Full-Scale Load Switch
ENSET
(1V/div)
ENSET
(1V/div)
OUT
(2V/div)
OUT
(2V/div)
VDIODE
(1V/div)
VDIODE
(2V/div)
IIN
(200mA/div)
IIN
(100mA/div)
Time (50µs/div)
Time (50µs/div)
Turn-Off
80mA Load Characteristics
VIN
20mV/div
ENSET
(1V/div)
VDIODE
(2V/div)
IIN
(100mA/div)
OUT
VDIODE
Time (200µs/div)
Time (1µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012
5
DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Functional Block Diagram
VIN
Soft Start
1.5X
Charge
Pump
1MHz
Oscillator
C1+
C1C2+
C2OUT
Voltage
Reference
EN/SET
S2Cwire
Interface
5
32x8 bit
ROM
8
Current
Mode
DAC
D
GND
Functional Description
The AAT3121 is a high efficiency 1.5X fractional charge
pump device intended for white LED backlight applications. The AAT3121 requires only four external components: two 1µF ceramic capacitors for the charge pump
flying capacitors (C1 and C2), one 1µF ceramic capacitor
for CIN, and one 0.33µF to 1µF ceramic capacitor for COUT.
The charge pump output is converted into a constant current output capable of driving up to six individual LEDs
with a maximum of 120mA. The current source output
magnitude is controlled by the EN/SET serial data interface. The interface records rising edges of the EN/SET pin
and decodes them into 32 individual current level set-
6
tings each 1dB apart (see Figure 1). Code 32 is full scale,
and Code 1 is full scale attenuated by 31dB. The modulo
32 interface wraps states back to State 1 after the 32nd
clock. With each EN/SET pulse, the output current
increases by 1dB. To decrease the output current by 1dB,
31 EN/SET clock pulses are required. The counter can be
clocked at speeds up to 1MHz, so intermediate states are
not visible. The first rising edge of EN/SET enables the IC
and initially sets the output LED current to -31dB, the
lowest setting: 3.3mA. Once the final clock cycle is input
for the desired brightness level, the EN/SET pin is held
high to maintain the device output current at the programmed level. The device is disabled 500µs after the
EN/SET pin transitions to a logic low state.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012
DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Applications Information
EN/SET Serial Interface
Current Level Settings
LED current level is set via the serial interface according
to a logarithmic scale where each code is 1dB greater
than the previous code. In this manner, the LED brightness appears linear with each increasing code. Table 1
depicts the relationship between each rising edge of the
EN/SET and the output current in mA.
Code
IOUT (mA)
Code
IOUT (mA)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
3.294
3.765
4.235
4.706
5.176
6.118
6.588
7.529
8.471
9.412
10.824
11.765
13.647
15.059
16.941
18.824
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
21.176
24.000
26.824
30.118
33.882
38.118
42.353
47.529
53.647
60.235
67.294
75.765
84.706
95.059
106.824
120.000
Table 1: Current Level Settings.
The current source output magnitude is controlled by the
EN/SET serial data interface. The interface records rising
edges of the EN/SET pin and decodes them into 32 individual current level settings each 1dB apart. Code 32 is
full scale, and Code 1 is full scale attenuated by 31dB.
The modulo 32 interface wraps states back to State 1
after the 32nd clock, so 1dB of attenuation is achieved
by clocking the EN/SET pin 31 times. The counter can be
clocked at speeds up to 1MHz, so intermediate states
are not visible. The first rising edge of EN/SET enables
the IC and initially sets the output LED current to -31dB,
the lowest setting: 3.3mA. Once the final clock cycle is
input for the desired brightness level, the EN/SET pin is
held high to maintain the device output current at the
programmed level. The device is disabled 500µs after
the EN/SET pin transitions to a logic low state.
The EN/SET timing is designed to accommodate a wide
range of data rates. After the first rising edge of EN/SET,
the charge pump is enabled and reaches full capacity
after the soft-start time (TSS). During the soft-start time,
multiple clock pulses may be entered on the EN/SET pin
to set the final output current level with a single burst of
clocks. Alternatively, the EN/SET clock pulses may be
entered one at a time to gradually increase the LED
brightness over any desired time period. A constant current is sourced as long as EN/SET remains in a logic high
state. The current source outputs are switched off after
EN/SET has remained in a low state for at least the TOFF
timeout period.
Normalized Current Level Settings
Normalized Current to Full Scale
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Code
Figure 1: Normalized Current Level Settings.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012
7
DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
EN/SET Timing Diagram
tLO
tHI
tOFF
EN/SET
Code
OFF
1
LED Selection
The AAT3121 is specifically intended for driving white
LEDs. However, the device design will allow the AAT3121
to drive most types of LEDs with forward voltage specifications ranging from 2.0V to 4.3V. LED applications
may include main and sub-LCD display backlighting,
camera photo-flash applications, color (RGB) LEDs,
infrared (IR) diodes for remotes, and other loads benefiting from a controlled output current generated from a
varying input voltage.
Device Switching Noise Performance
The AAT3121 operates at a fixed frequency of approximately 1MHz to control noise and limit harmonics that
can interfere with the RF operation of cellular telephone
handsets or other communication devices. Back-injected
noise appearing on the input pin of the charge pump is
20mV peak-to-peak, typically ten times less than inductor-based DC/DC boost converter white LED backlight
solutions. The AAT3121 soft-start feature prevents noise
transient effects associated with inrush currents during
start-up of the charge pump circuit.
Power Efficiency and Device Evaluation
Due to the unique charge pump circuit architecture and
design of the AAT3121, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
Since the AAT3121 output is purely constant current
source, it is difficult to measure the output voltage to
derive an overall output power measurement. For any
given application, white LED forward voltage levels can
differ, yet the output drive current will be maintained as
a constant.
8
2
3
OFF
This makes quantifying output power a difficult task
when taken in the context of comparing to other white
LED driver circuit topologies. A better way to quantify
total device efficiency is to observe the total input power
to the device for a given LED current drive level. The
best white LED driver for a given application should be
based on trade-offs of size, external components count,
reliability, operating range, and total energy usage...not
just % efficiency.
Charge Pump Efficiency
The AAT3121 is a fractional charge pump. The efficiency
(h) can be simply defined as a linear voltage regulator
with an effective output voltage that is equal to one and
one half times the input voltage. Efficiency (h) for an
ideal 1.5X charge pump can typically be expressed as
the output power divided by the input power.
η=
POUT
PIN
In addition, with an ideal 1.5X charge pump, the output
current may be expressed as 2/3 of the input current.
The expression to define the ideal efficiency (h) can be
rewritten as:
η=
POUT
VOUT · IOUT
VOUT
=
=
PIN
VIN · 1.5IOUT 1.5VIN
-or-
η(%) = 100
VOUT
1.5VIN
For a charge pump with an output of 5V and a nominal
input of 3.5V, the theoretical efficiency is 95%. Due to
internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at 93%.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012
DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
These figures are in close agreement for output load
conditions from 3.0mA to 120mA. Efficiency will decrease
as load current drops below 0.05mA or when level of VIN
approaches VOUT. Refer to the Typical Characteristics section of this datasheet for measured plots of efficiency
versus input voltage and output load current for the
given charge pump output voltage options.
Capacitor Selection
Careful selection of the four external capacitors CIN, C1,
C2, and COUT is important because they will affect turn-on
time, output ripple, and transient performance. Optimum
performance will be obtained when low equivalent series
resistance (ESR) ceramic capacitors are used. In general, low ESR may be defined as less than 100mW. A
value of 1µF for all four capacitors is a good starting
point when choosing capacitors. If the LED current
sources are only programmed for light current levels,
then the capacitor size may be decreased.
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with
AAT3121 products. Ceramic capacitors offer many
advantages over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very
low ESR, is lowest cost, has a smaller PCB footprint, and
is non-polarized. Low ESR ceramic capacitors help maximize charge pump transient response. Since ceramic
capacitors are non-polarized, they are not prone to
incorrect connection damage.
Equivalent Series Resistance: ESR is an important
characteristic to consider when selecting a capacitor.
ESR is a resistance internal to a capacitor that is caused
by the leads, internal connections, size or area, material
composition, and ambient temperature. Capacitor ESR is
typically measured in milliohms for ceramic capacitors
and can range to more than several ohms for tantalum
or aluminum electrolytic capacitors.
Ceramic Capacitor Materials: Ceramic capacitors less
than 0.1µF are typically made from NPO or C0G materials. NPO and C0G materials typically have tight tolerance and are stable over temperature. Large capacitor
values are typically composed of X7R, X5R, Z5U, or Y5V
dielectric materials. Large ceramic capacitors, typically
greater than 2.2µF are often available in low-cost Y5V
and Z5U dielectrics, but large capacitors are not required
in the AAT3121 application.
Capacitor area is another contributor to ESR. Capacitors
that are physically large will have a lower ESR when compared to an equivalent material smaller capacitor. These
larger devices can improve circuit transient response
when compared to an equal value capacitor in a smaller
package size.
Thermal Protection
The AAT3121 has a thermal protection circuit that will
shut down the charge pump and current outputs if the
die temperature rises above the thermal limit due to
short-circuit conditions.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012
9
DATA SHEET
AAT3121
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TSOPJW-12
JQXYY
AAT3121ITP-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information
TSOPJW-12
2.85 ± 0.20
2.40 ± 0.10
0.20 + 0.10
- 0.05
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
7° NOM
0.055 ± 0.045
0.04 REF
0.15 ± 0.05
+ 0.10
1.00 - 0.065
0.9625 ± 0.0375
3.00 ± 0.10
4° ± 4°
0.45 ± 0.15
0.010
2.75 ± 0.25
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a
service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no
responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes.
No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided hereunder, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale.
THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR
PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES
NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM
THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper
use or sale.
Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product
design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters.
Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for
identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference.
10
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202131A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 4, 2012