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LP55281
SNVS458D – JUNE 2007 – REVISED OCTOBER 2016
LP55281 12-Channel RGB/White-LED Drive With SPI, I2C Interface
1 Features
3 Description
•
•
•
•
•
•
The LP55281 device is a quadruple RGB LED driver
for handheld devices. It can drive 4 RGB LED sets
and a single fun-light LED. The boost DC-DC
converter drives high current loads with high
efficiency. The RGB driver can drive individual color
LEDs or RGB LEDs powered from boost output or
external supply. Built-in audio synchronization feature
allows user to synchronize the fun-light LED to audio
inputs. The flexible SPI or I2C interface allows easy
control of LP55281. A small YZR0036 or YPG0036
package, together with minimum number of external
components, is a best fit for handheld devices. The
LP55281 also has an LED test feature, which can be
used, for example, in production for checking the LED
connections.
1
Audio Synchronization for a Single Fun-Light LED
Four PWM Controlled RGB LED Drivers
High-Efficiency Boost DC-DC Converter
SPI or I2C-Compatible Interface
Two Addresses in I2C-Compatible Interface
LED Connectivity Test Through the Serial
Interface
2 Applications
•
•
Cellular Phones
PDAs, MP3 Players
Device Information(1)
PART NUMBER
LP55281
PACKAGE
DSBGA (36)
BODY SIZE (NOM)
2.982 mm × 2.982 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application
IMAX = 300...400 mA
Lboost
+
CIN
CVDD
-
10 PF
100 nF
CVDDA
1 éF
BATTERY
CREF
VOUT = 4...5.3V
D1
4.7 PH
SW
VDD1
VDD2
VDDA
RRT
MCU
CVDDIO
100 nF
FB
RGB1
G1
VREF
B1
IRGB
RGB2
IRT
R2
SO
SI/A0
SCK/SCL
G2
SS/SDA
NRST
VDDIO
10 PF
R1
100 nF
RRGB
COUT
B2
LP55281
RGB3
R3
G3
IF_SEL
B3
RGB4
R4
G4
B4
ASE1
ALED
ASE2
AUDIO
INPUTS
GNDs
Copyright © 2016, Texas Instruments Incorporated
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LP55281
SNVS458D – JUNE 2007 – REVISED OCTOBER 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
7
1
1
1
2
3
5
Absolute Maximum Ratings ...................................... 5
ESD Ratings.............................................................. 5
Recommended Operating Conditions....................... 5
Thermal Information .................................................. 6
Electrical Characteristics........................................... 6
SPI Timing Requirements ......................................... 9
I2C Timing Requirements ....................................... 10
Boost Converter Typical Characteristics................. 11
RGB Driver Typical Characteristics ........................ 12
Detailed Description ............................................ 13
7.1
7.2
7.3
7.4
Overview .................................................................
Functional Block Diagram .......................................
Feature Description.................................................
Device Functional Modes........................................
13
14
15
23
7.5 Programming........................................................... 25
7.6 Register Maps ......................................................... 30
8
Application and Implementation ........................ 31
8.1 Application Information............................................ 31
8.2 Typical Application ................................................. 31
8.3 Initialization Set Up Example .................................. 34
9 Power Supply Recommendations...................... 34
10 Layout................................................................... 35
10.1 Layout Guidelines ................................................. 35
10.2 Layout Example .................................................... 36
11 Device and Documentation Support ................. 37
11.1
11.2
11.3
11.4
11.5
11.6
11.7
Device Support......................................................
Related Documentation .......................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
37
37
37
37
37
37
37
12 Mechanical, Packaging, and Orderable
Information ........................................................... 37
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (March 2013) to Revision D
Page
•
Added Device Information and Pin Configuration and Functions sections, ESD Ratings and Thermal Information
tables, Feature Description, Device Functional Modes, Application and Implementation, Power Supply
Recommendations, Layout, Device and Documentation Support, and Mechanical, Packaging, and Orderable
Information sections; update title............................................................................................................................................ 1
•
Added NRST pin connection to MCU on Simplified Schematic ............................................................................................ 1
•
Changed RθJA for YPG package from "60°C/W" to "48.9°C/W"and for YZR package from "60°C/W" to "49.1°C/W"............ 6
Changes from Revision B (March 2013) to Revision C
•
2
Page
Changed layout of National Semiconductor data sheet to TI format...................................................................................... 1
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SNVS458D – JUNE 2007 – REVISED OCTOBER 2016
5 Pin Configuration and Functions
YPG and YZR Packages
36-Pin DSBGA
Top View
YPG and YZR Packages
36-Pin DSBGA
Bottom View
B1
G1
R1
B3
FB
SW
6
SW
FB
B3
R1
G1
B1
6
GND_
RGB1
IRGB
SS/
SDA
G3
R3
GND_
SW
5
GND_
SW
R3
G3
SS/
SDA
IRGB
GND_
RGB1
5
R2
SO
SI/A0
ASE2
GND
GND_
RGB2
4
GND_
RGB2
GND
ASE2
SI/A0
SO
R2
4
G2
SCK/
SCL
VDDI
O
VDD1
R4
NRST
3
NRST
R4
VDD1
VDDI
O
SCK/
SCL
G2
3
B2
IF_
SEL
IRT
ASE1
G4
ALED
2
ALED
G4
ASE1
IRT
IF_
SEL
B2
2
VDD2
VDDA
VREF
GNDA
B4
GND
1
GND
B4
GNDA
VREF
VDDA
VDD2
1
A
B
C
D
E
F
F
E
D
C
B
A
Pin Functions
PIN
NUMBER
NAME
1A
VDD2
1B
1C
TYPE
DESCRIPTION
Power
Supply voltage
VDDA
Power
Internal LDO output
VREF
Output
Reference voltage
1D
GNDA
Ground
Ground for analog circuitry
1E
B4
Output
Blue LED 4 output
1F
GND
Ground
Ground
2A
B2
Output
Blue LED 2 output
2B
IF_SEL
Logic Input
2C
IRT
Input
Oscillator frequency resistor
2D
ASE1
Input
Audio synchronization input 1
2E
G4
Output
Green LED 4 output
2F
ALED
Output
Audio Synchronized LED oautput
3A
G2
Output
Green LED 2 output
3B
SCK/SCL
Logic Input
3C
VDDIO
Power
Supply voltage for input/output buffers and drivers
3D
VDD1
Power
Supply voltage
3E
R4
Output
Red LED 4 output
3F
NRST
Input
Interface (SPI or I2C compatible) selection (IF_SEL = 1 for SPI)
Clock (SPI/I2C)
Asynchronous reset, active low
4A
R2
Output
4B
SO
Logic Output
Red LED 2 output
4C
SI/A0
Logic Input
4D
ASE2
Input
4E
GND
Ground
Ground
4F
GND_RGB2
Ground
Ground for RGB3-4 currents
5A
GND_RGB1
Ground
Ground for RGB1-2 currents
Serial data out (SPI)
Serial input (SPI), address select (I2C)
Audio synchronization input 2
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Pin Functions (continued)
PIN
NUMBER
NAME
TYPE
DESCRIPTION
5B
IRGB
Input
5C
SS/SDA
Logic Input/Output
Bias current set resistor for RGB drivers
5D
G3
Output
Green LED 3 output
Slave select (SPI), Serial data in/out (I2C)
5E
R3
Output
Red LED 3 output
5F
GND_SW
Ground
Power switch ground
6A
B1
Output
Blue LED 1 output
6B
G1
Output
Green LED 1 output
6C
R1
Output
Red LED 1 output
6D
B3
Output
Blue LED 3 output
6E
FB
Input
6F
SW
Output
4
Boost converter feedback
Boost converter power switch
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SNVS458D – JUNE 2007 – REVISED OCTOBER 2016
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2) (3)
V (SW, FB, R1-4, G1-4, B1-4, ALED) (4)
(5)
VVDD1, VVDD2, VVDDIO, VVDDA
MIN
MAX
UNIT
–0.3
7.2
V
–0.3
6
V
Voltage on ASE1-2, IRT, IRGB, VREF
–0.3 to VVDD1 + 0.3 V with 6 V maximum
Voltage on logic pins
–0.3 to VVDDIO + 0.3 V with 6 V maximum
V (all other pins): voltage to GND
–0.3
6
I (VREF)
10
µA
I (R1-4, G1-4, B1-4)
100
mA
150
°C
150
°C
Continuous power dissipation (6)
Internally limited
Junction temperature, TJ-MAX
Storage temperature, Tstg
(1)
(2)
(3)
(4)
(5)
(6)
–65
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltages are with respect to the potential at the GND pins.
If Military/Aerospace specified devices are required, contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
Battery/Charger voltage must be above 6 V, and no more than 10% of the operational lifetime.
Voltage tolerance of LP55281 above 6 V relies on fact that VVDD1 and VVDD2 (2.8 V) are available (ON) at all conditions. If VVDD1 and
VVDD2 are not available (ON) at all conditions, Texas Instruments does not ensure any parameters or reliability for this device.
Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 160°C (typical) and
disengages at TJ = 140°C (typical)
6.2 ESD Ratings
V(ESD)
(1)
Electrostatic discharge
VALUE
UNIT
±2000
V
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process..
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
V (SW, FB, R1-4, G1-4, B1-4, ALED)
NOM
MAX
UNIT
0
6
V
VVDD1,2 with external LDO
2.7
5.5
V
VVDD1,2 with internal LDO
3
5.5
V
2.7
2.9
V
VVDDIO
1.65
VVDD1
Voltage on ASE1-2
0.1 V to VVDDA – 0.1 V
VDDA
Recommended load current
Junction temperature, TJ
Ambient temperature, TA
(1)
(2)
(2)
0
300
mA
–30
125
°C
–30
85
°C
All voltages are with respect to the potential at the GND pins.
In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may
have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP =
125°C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to-ambient thermal resistance of the
part/package in the application (RθJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (RθJA x PD-MAX).
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6.4 Thermal Information
LP55281
THERMAL METRIC (1)
YPG (DSGBA)
YZR (DSGBA)
36 PINS
36 PINS
UNIT
48.9
49.1
°C/W
RθJA
Junction-to-ambient thermal resistance
RθJC(top)
Junction-to-case (top) thermal resistance
0.2
0.2
°C/W
RθJB
Junction-to-board thermal resistance
10.6
10.8
°C/W
ψJT
Junction-to-top characterization parameter
0.1
0.1
°C/W
ψJB
Junction-to-board characterization parameter
10.4
10.6
°C/W
(1)
For more information about traditional and new thermal metrics, see Semiconductor and IC Package Thermal Metrics.
6.5 Electrical Characteristics
Unless otherwise noted, specifications apply to Functional Block Diagram with: VVDD1 = VVDD2 = 3.6 V, VVDDIO = 2.8 V, CVDD =
CVDDIO = 100 nF, COUT = CIN = 10 µF, CVDDA= 1 µF, CREF = 100 nF, L1 = 4.7 µH, RRGB = 8.2 kΩ and RRT = 82 kΩ, and limits are
for TJ = 25°C. (1) (2) (3).
PARAMETER
TEST CONDITIONS
MIN
NSTBY = L
SCK = SS = SI = H
NRST = L
TYP
1
Standby supply current (VDD1
+ VDD2 + leakage to SW, FB, NSTBY = L
RGB1-4, ALED)
SCK = SS = SI = H
NRST = L
–30°C < TA < 85°C
No-boost supply current
(VDD1 + VDD2)
IVDD
(1)
(2)
(3)
(4)
6
µA
10
NSTBY = H, EN_BOOST = L
SCK = SS = SI = H
Audio synchronization and LEDs OFF
µA
NSTBY = H, EN_BOOST = H, SCK = SS =
No-load supply current (VDD1 SI = H
+ VDD2)
Audio synchronization and LEDs OFF
Autoload OFF
0.6
mA
Total RGB drivers quiescent
current (VDD1 + VDD2)
EN_RGBx = H
250
µA
ALED[7:0] = FFh
180
µA
ALED[7:0] = 00h
0
µA
Audio synchronization ON
VDD1,2 = 2.8 V
390
µA
Audio synchronization ON
VDD1,2 = 3.6 V
700
µA
Audio synchronization
current (VDD1 + VDD2)
VDDA
UNIT
350
ALED driver current (VDD1 +
VDD2)
IDDIO
MAX
NSTBY = L
VDDIO standby supply current SCK = SS = SI = H
–30°C < TA < 85°C
VDDIO supply current
1 MHz SCK frequency in SPI modeCL = 50
pF at SO pin
Output voltage of internal
LDO for analog parts
See (4)
1
20
–3%
2.8
µA
µA
3%
V
All voltages are with respect to the potential at the GND pins.
Minimum (MIN) and maximum (MAX) limits are ensured by design, test or statistical analysis. Typical (TYP) numbers are not ensured,
but do represent the most likely norm.
Low-ESR surface-mount ceramic capacitors (MLCCs) used in setting electrical characteristics.
VDDA output is not recommended for external use.
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Electrical Characteristics (continued)
Unless otherwise noted, specifications apply to Functional Block Diagram with: VVDD1 = VVDD2 = 3.6 V, VVDDIO = 2.8 V, CVDD =
CVDDIO = 100 nF, COUT = CIN = 10 µF, CVDDA= 1 µF, CREF = 100 nF, L1 = 4.7 µH, RRGB = 8.2 kΩ and RRT = 82 kΩ, and limits are
for TJ = 25°C.(1)(2) (3).
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
MAGNETIC BOOST DC-DC CONVERTER ELECTRICAL CHARACTERISTICS
ILOAD
VOUT
Recommended load current
3 V ≤ VIN
VOUT = 5 V
0
300
mA
3 V ≤ VIN
VOUT = 4 V
0
400
mA
–5%
5%
Output voltage accuracy
(FB pin)
3 V ≤ VIN ≤ VOUT – 0.5 V
VOUT = 5 V
–30°C < TA < 85°C
Output voltage (FB pin)
1 mA ≤ ILOAD ≤ 300 mA
VIN > VOUT + VSchottky (5)
VIN –
VSchottky
VDD1,2 = 3 V, ISW = 0.5 A
RDSON
Switch ON resistance
VDD1,2 = 3 V, ISW = 0.5 A
–30°C < TA < 85°C
PWM mode switching
frequency
RT = 82 kΩ
freq_sel[2:0] = 1XX
fBoost
Frequency accuracy
V
0.4
Ω
0.8
2
2.7 V ≤ VDDA ≤ 2.9 V
RT = 82 kΩ ± 1%
–7%
2.7 V ≤ VDDA ≤ 2.9 V
RT = 82 kΩ ± 1%
–30°C < TA < 85°C
–10%
±3%
MHz
7%
10%
tPULSE
Switch pulse minimum width
no load
30
ns
tSTART-UP
Start-up time
Boost start-up from STANDBY (6)
10
ms
ISW_MAX
SW pin current limit
700
–30°C < TA < 85°C
800
550
900
950
mA
RGB DRIVER ELECTRICAL CHARACTERISTICS (R1-4, G1-4, B1-4)
Ileakage
5.5 V at measured pin
R1-4, G1-4, B1-4 pin leakage
5.5 V at measured pin
current
–30°C < TA < 85°C
0.1
1
Maximum recommended sink Limited with external resistor RRGB
current
–30°C < TA < 85°C
IRGB
fPWM
40
Accuracy at 15 mA
RRGB = 8.2 kΩ ± 1%
Current mirror ratio
See (6)
RGB1-4 current mismatch
IRGB = 15 mA
±5%
RGB switching frequency
Accuracy defined by internal oscillator,
frequency value selectable
fPWM
µA
mA
±5%
1 : 100
AUDIO SYNCHRONIZATION INPUT ELECTRICAL CHARACTERISTICS
ZIN
Input Impedance of ASE1,
ASE2
AIN
ASE1, ASE2 audio input
level range (peak-to-peak)
See (6)
10
Min input level needs maximum gain; Max
input level for minimum gain
15
0
kΩ
1600
mV
ALED DRIVER ELECTRICAL CHARACTERISTICS
VALED = 5.5 V
Ileakage
Leakage current
IALED
ALED current tolerance
0.03
VALED = 5.5 V
–30°C < TA < 85°C
1
IALED set to 13.2 mA
(5)
(6)
IALED set to 13.2 mA
–30°C < TA < 85°C
13.2
µA
mA
11.9
14.5
–10%
10%
mA
When VIN rises above VOUT + VSchottky, VOUT starts to follow the VIN voltage rise so that VOUT = VIN – VSchottky.
Data ensured by design.
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Electrical Characteristics (continued)
Unless otherwise noted, specifications apply to Functional Block Diagram with: VVDD1 = VVDD2 = 3.6 V, VVDDIO = 2.8 V, CVDD =
CVDDIO = 100 nF, COUT = CIN = 10 µF, CVDDA= 1 µF, CREF = 100 nF, L1 = 4.7 µH, RRGB = 8.2 kΩ and RRT = 82 kΩ, and limits are
for TJ = 25°C.(1)(2) (3).
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
0.2 ×
VDDIO
V
LOGIC INTERFACE CHARACTERISTICS
VIL
Input low level
–30°C < TA < 85°C
VIH
Input high level
–30°C < TA < 85°C
0.8 ×
VDDIO
II
Logic input current
–30°C < TA < 85°C
–1
fSCK/SCL
Clock frequency
V
1
µA
I2C, –30°C < TA < 85°C
400
kHz
–30°C < TA < 85°C
SPI mode, VDDIO > 1.8 V
13
MHz
5
MHz
–30°C < TA < 85°C
SPI mode,
1.65V ≤ VDDIO < 1.8V
LOGIC INPUT NRST
VIL
Input low level
–30°C < TA < 85°C
VIH
Input high level
–30°C < TA < 85°C
1.2
II
Logic input current
–30°C < TA < 85°C
–1
tNRST
Reset pulse width
–30°C < TA < 85°C
10
0.5
V
1
µA
V
µs
LOGIC OUTPUT SO
ISO = 3 mA VDDIO > 1.8 V
VOL
Output low level
0.3
ISO = 3 mA VDDIO > 1.8 V
–30°C < TA < 85°C
0.5
ISO = 2 mA, 1.65V ≤ VDDIO < 1.8 V
ISO = 2 mA, 1.65V ≤ VDDIO < 1.8 V
–30°C < TA < 85°C
0.5
VDDIO –
0.3
ISO = –3 mA, VDDIO > 1.8 V
VOH
Output high level
ISO = –3 mA, VDDIO > 1.8 V
–30°C < TA < 85°C
VDDIO –
0.5
IL
Output leakage current
V
VDDIO –
0.3
ISO = –2 mA, 1.65V ≤ VDDIO < 1.8 V
ISO = –2 mA, 1.65V ≤ VDDIO < 1.8 V
–30°C < TA < 85°C
V
0.3
VDDIO –
0.5
VSO = 2.8 V, –30°C < TA < 85°C
1
µA
LOGIC OUTPUT SDA
VOL
8
Output low level
ISDA = 3 mA
ISDA = 3 mA, –30°C < TA < 85°C
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0.3
0.5
V
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6.6 SPI Timing Requirements
VDD = VDDIO = 2.8 V (1)
MIN
MAX
UNIT
1
Cycle time
70
ns
2
Enable lead time
35
ns
3
Enable lag time
35
ns
4
Clock low time
35
ns
5
Clock high time
35
ns
6
Data setup time
20
ns
7
Data hold time
0
ns
8
Data access time
20
ns
9
Disable time
10
ns
10
Data valid
20
ns
11
Data hold time
(1)
0
ns
Data ensured by design.
SS
2
5
1
SCK
3
4
12
7
6
SI
MSB IN
BIT 14
BIT 9
BIT 8
BIT 1
BIT 7
8
11
10
MSB OUT
SO
Address
R/W
LSB IN
BIT 1
9
LSB OUT
Data
Figure 1. SPI Timing Diagram
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6.7 I2C Timing Requirements
VDD1,2 = 3 V to 4.5 V, VDDIO = 1.65 V to VDD1,2
(1)
MIN
MAX
UNIT
1
Hold time (repeated) START condition
0.6
µs
2
Clock low time
1.3
µs
3
Clock high time
600
ns
4
Setup time for a repeated START Condition
600
ns
5
Data hold time
50
ns
6
Data setup time
100
7
Rise time of SDA and SCL
20 + 0.1Cb
300
ns
8
Fall time of SDA and SCL
15 + 0.1Cb
300
ns
9
Set-up time for STOP condition
600
ns
10
Bus free time between a STOP and a START condition
1.3
µs
Cb
Capacitive load for each bus line
10
(1)
ns
200
pF
Data ensured by design.
SDA
10
8
7
6
1
8
2
7
SCL
1
5
3
4
9
Figure 2. I2C Timing Diagram
10
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6.8 Boost Converter Typical Characteristics
660.0
91.0
ILOAD = 100 mA
91.0
BATTERY CURRENT (mA)
EFFICIENCY (%)
88.6
88.6
86.2
86.2 200 mA
83.8
83.8
ILOAD = 300 mA
660.0
300 mA
81.4
81.4
79.0 350 mA
fBOOST = 2.0 MHz
588.0
588.0
VOUT = 4V
516.0
516.0
VOUT = 5.3V
444.0
444.0
VOUT = 4.7V
372.0
372.0
300.0
300.0
79.0
3.0
3.3
3.6
3.9
4.2
3.0
4.5
INPUT VOLTAGE (V)
3.6
4.1
4.7
5.2
BATTERY VOLTAGE (V)
Figure 3. Boost Converter Efficiency
Figure 4. Battery Current vs Voltage
BATTERY CURRENT (mA)
310.0
ILOAD = 150 mA
310.0
278.0
278.0
VOUT = 4V
246.0
246.0
VOUT = 4.7V
214.0
214.0
VOUT = 5.3V
182.0
150.0
150.0
182.0
3.0
3.6
4.1
4.7
5.2
BATTERY VOLTAGE (V)
Figure 6. Boost Frequency vs RT Resistor
Figure 5. Battery Current vs Voltage
5.1
OUTPUT VOLTAGE (V)
5.1
4.8
4.8
4.5
4.5
4.2
4.2
VIN = 3.6V
f = 2 MHz
L -TDK VLF4012AT 4.7 éH
CIN = COUT = 10 éF
3.9
3.9
3.6
3.6
0.0
140.0
280.0
420.0
560.0
700.0
OUTPUT CURRENT (mA)
Figure 7. Output Voltage vs Load Current
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6.9 RGB Driver Typical Characteristics
24.0
24.0
CURRENT (mA)
19.2
19.2
T = -40°C
14.4
14.4
T = 25°C
T = 85°C
9.6
9.6
4.8
RRGB = 5.3 kÖ
4.8
0.0
0.0
0.0
120.0
240.0
360.0
480.0
600.0
VOLTAGE (V)
Figure 8. Output Current vs Pin Voltage
(Current Sink Mode)
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Figure 9. Output Current vs RRGB
(Current Sink Mode)
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7 Detailed Description
7.1 Overview
The LP55281 boost DC-DC converter generates a 4-V to 5.3-V supply voltage for the LEDs from single Li-Ion
battery (3 V...4.5 V). The output voltage is controlled with an 8-bit register in 9 steps. The converter is a magnetic
switching PWM mode DC-DC converter with a current limit. When timing resistor RT is 82 kΩ, the converter has
three options for switching frequency: 1 MHz, 1.67 MHz, and 2 MHz (default). Timing resistor defines the internal
oscillator frequency and thus directly affects boost frequency and all internally generated timing (RGB, ALED) of
the circuit.
The LP55281 boost converter uses pulse-skipping elimination to stabilize the noise spectrum. Even with light
load or no load a minimum length current pulse is fed to the inductor. An active load is used to remove the
excess charge from the output capacitor at very light loads. At very light load and when input and output voltages
are very close to each other, the pulse skipping is not completely eliminated. Output voltage must be at least
0.5 V higher than input voltage to avoid pulse skipping. Reducing the switching frequency also reduces the
required voltage difference.
Active load can be disabled with the EN_AUTOLOAD bit. Disabling increases the efficiency at light loads, but the
downside is that pulse skipping will occur. The boost converter must be stopped when there is no load to
minimize the current consumption.
The topology of the magnetic boost converter is called current programmed mode (CPM) control, where the
inductor current is measured and controlled with the feedback. The user can program the output voltage of the
boost converter. The output voltage control changes the resistor divider in the feedback loop.
Figure 10 shows the boost topology with the protection circuitry. Four different protection schemes are
implemented:
1. Overvoltage protection — limits the maximum output voltage
– Keeps the output below breakdown voltage.
– Prevents boost operation if battery voltage is much higher than desired output.
2. Overcurrent protection — limits the maximum inductor current
– Voltage over switching NMOS is monitored; too high voltages turn the switch off.
3. Feedback break protection — prevents uncontrolled operation if FB pin gets disconnected.
4. Duty cycle limiting, done with digital control.
2 MHz clock
VIN
Duty control
VOUT
SW
FBNCCOMP
FB
+
-
R
S
R
OVPCOMP
+
-
R
SWITCH
RESETCOMP
+
ERRORAMP
VREF
SLOPER
+
-
+
-
R
+
-
R
OLPCOMP
ACTIVE
LOAD
LOOPC
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Figure 10. Boost Converter Topology
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7.2 Functional Block Diagram
LBoost
IMAX = 300...400 mA
VOUT = 4...5.3 V
D1
4.7 µH
+ -
SW
FB
COUT
10 µF
VDD1
CVDD
CIN
10 µF 100 nF VDD2
Logic supply
BG
PWM
Li-Ion
Battery
Or
Charger
VDDA
LDO
POR
GND_SW
VREF
CVDDA
1 µF
CREF
100 nF
BOOST
REF
THSD
BIAS
OSC
R1
IRGB
G1
IRT
B1
RRGB
RRT
R2
CONTROL
MCU
SS/SDA
IF_SEL
NRST
INTERFACE
SCK/SCL
LED CONNECTIVITY TEST MUX
SO
SI/A0
PWM
CTRL
SPI
I2C
VDDIO
CVDDIO
100 nF
SINGLE
ENDED
ANALOG
AUDIO
G2
B2
GND_RGB2
R3
RGB
Up to
40 mA/
LED
G3
B3
R4
G4
ASE1
B4
AUDIO
SYNC
GND_RGB1
ASE2
8-Bit IDAC
ALED
D
A
D
Audio
Synchronized
LED up to
15 mA
A
GNDA
GND
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7.3 Feature Description
7.3.1 Magnetic Boost DC-DC Converter
7.3.1.1 Boost Standby Mode
User can stop the boost converter operation by writing the Enables register bit EN_BOOST low. When
EN_BOOST is written high, the converter starts for 10 ms in PFM mode and then goes to PWM mode.
7.3.1.2 Boost Output Voltage Control
User can control the Boost output voltage by boost output 8-bit register.
BOOST OUTPUT [7:0] Register 0Fh
BOOST OUTPUT VOLTAGE (TYPICAL)
Bin
Hex
0000 0000
00
4V
0000 0001
01
4.25 V
0000 0011
03
4.4 V
0000 0111
07
4.55 V
0000 1111
0F
4.7 V
0001 1111
1F
4.85 V
0011 1111
3F
5 V (default)
0111 1111
7F
5.15 V
1111 1111
FF
5.3 V
OUTPUT VOLTAGE (200 mV /D IV )
5.4
5.2
5.0
4.8
4.6
4.4
V IN = 3.6V
I LOAD = 50 mA
4.2
Control = 00 :)):00
4.0
0
0.2
0.4
0.6
0.8
1. 0
1. 2
1.4
TIME( 200Ps/DIV)
Figure 11. Boost Output Voltage Control
7.3.1.3 Boost Frequency Control
Register-frequency selections (address 10h). Register default value after reset is 07h.
FRQ_SEL[2:0]
FREQUENCY
1XX
2 MHz
01X
1.67 MHz
001
1 MHz
7.3.2 Functionality of RGB LED Outputs (R1-4, G1-4, B1-4)
The LP55281 device has 4 sets of RGB/color LED outputs. Each set has 3 outputs, which can be controlled
individually with a 6-bit PWM control register. The pulsed current level for each LED output is set with a single
external resistor RRGB and a 2-bit coarse adjustment bit for each LED output (see Table 1 and Table 2).
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Table 1. LED Current Level Adjust
Rx_IPLS[7:6], Gx_IPLS[7:6], Bx_IPLS[7:6]
SINK CURRENT PULSE (IMAX = 100 × 1.23 / RRGB) – IPLS
00
0.25 × IMAX
01
0.50 × IMAX
10
0.75 × IMAX
11
1.00 × IMAX
Table 2. LED PWM Control
Rx_PWM[5:0], Gx_PWM[5:0], Bx_PWM[5:0]
AVERAGE SINK CURRENT
PULSE RATIO (%)
000 000
0
0
000 001
1/63 × IPLS
1.6
000 010
2/63 × IPLS
3.2
...
...
...
111 110
62/63 × IPLS
98.4
111 111
63/63 × IPLS
100
Each RGB set must be enabled separately by setting EN_RGBx bit to 1. The device must be enabled (NSTBY =
1) before the RGB outputs can be activated.
When any of EN_RGBx bits are set to 1 and NSTBY = 1, the RGB driver takes a certain quiescent current from
battery even if all PWM control bits are 0. The quiescent current is dependent on RRGB resistor, and can be
calculated from formula IR_RGB = 1.23 V / RRGB.
7.3.2.1 PWM Control Timing
PWM frequency can be selected from 3 predefined values: 10 kHz, 20 kHz, and 40 kHz. The frequency is
selected with FPWM1 and FPWM0 bits, see Table 3.
Table 3. PWM Frequency
16
FPWM1
FPWM0
0
0
9.92 kHz
0
1
19.84 kHz
1
0
39.68 kHz
1
1
39.68 kHz
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PWM FREQUENCY (fPWM)
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Each RGB set has equivalent internal PWM timing between R, G, and B: R has a fixed start time, G has a fixed
mid-pulse time, and B has a fixed-pulse end time. PWM start time for each RGB set is different in order to
minimize the instantaneous current loading due to the current sink switch on transition. See Figure 12 for details.
1 / fPWM
R1
G1
B1
R2
G2
B2
R3
G3
B3
R4
G4
B4
Figure 12. Timing Diagram
7.3.3 Audio Synchronization
The ALED output can be synchronized to incoming audio with an audio-synchronization feature. Audio
synchronization synchronizes ALED based on the peak amplitude of the input signal. Programmable gain and
automatic gain control function are also available for adjustment of input signal amplitude to light response.
Control of ALED brightness refreshing frequency is done with four different frequency configurations. The
digitized input signal has DC component that is removed by a digital DC-remover (–3 dB at 500 Hz). LP55281
has a 2-channel audio (stereo) input for audio synchronization, as shown in Figure 13. The inputs accept signals
in the range of 0 V to 1.6 V peak-to-peak, and these signals are mixed into a single wave so that they can be
filtered simultaneously.
LP55281 audio synchronization is mainly realized digitally, and it consists of the following signal path blocks (see
Figure 13):
• Input buffer
• AD converter
• Automatic gain control (AGC) and manually programmable gain
• Peak detector
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EN_AGC
GAIN_SEL[2:0]
SPEED_CTRL[1:0]
ASE1
15k
ADC
ASE2
15k
Threshold
&
AGC
PEAK
DETECTOR
HOLD
ALED
CONTROL
THRESHOLD[3:0]
Figure 13. ALED Audio Synchronization
7.3.3.1 Control of Audio Synchronization
Table 4 describes the controls required for audio synchronization. ALED brightness control through serial
interface is not available when audio synchronization is enabled.
Table 4. Audio Synchronization Control (Registers 0Dh And 0Eh)
NAME
BIT
DESCRIPTION
GAIN_SEL[2:0]
Register 0Dh
Bits 7-5
Input signal gain control. Gain has a range from 0 dB to -46 dB.
[000] = 0 dB, [001] = –6 dB, [010] = –12 dB, [011] = –18 dB,
[100] = -24 dB, [101] = -31 dB, [110] = -37 dB, [111] = –46 dB
DC_FREQ
Register 0Dh
Bit 4
Control of the high-pass filter's corner frequency:
0 = 80 Hz
1 = 510 Hz
EN_AGC
Register 0Dh
Bits 3
Automatic gain control. Set EN_AGC = 1 to enable automatic control or 0 to
disable. When EN_AGC is disabled, the audio input signal gain value is defined by
GAIN_SEL.
EN_SYNC
Register 0Dh
Bits 2
Audio synchronization enabled. Set EN_SYNC = 1 to enable audio
synchronization or 0 to disable.
SPEED_CTRL[1:0]
Register 0Dh
Bits 1-0
Control for refreshing frequency. Sets the typical refreshing rate for the ALED
output
[00] = FASTEST, [01] = 15 Hz, [10] = 7.6 Hz, [11] = 3.8 Hz
THRESHOLD[3:0]
Register 0Eh
Bits 3-0
Control for the audio input threshold. Sets the typical threshold for the audio inputs
signals. May be needed if there is noise on the audio lines.
Table 5. Audio Input Threshold Setting (Register 0Eh)
18
THRESHOLD[3:0]
THRESHOLD LEVEL (mV, typical)
0000
Disabled
0001
0.2
0010
0.4
...
...
1110
2.5
1111
2.7
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Table 6. Typical Gain Values vs Audio Input Amplitude
AUDIO INPUT AMPLITUDE mVP-P
GAIN VALUE (dB)
0 to 10
0
0 to 20
–6
0 to 40
–12
1 to 85
–18
3 to 170
–24
5 to 400
–31
10 to 800
–37
20 to 1600
–46
7.3.3.2 ALED Driver
The LP55281 device has a single ALED driver. It is a constant current sink with an 8-bit control. ALED driver can
be used as a DC current sink or an audio synchronized current sink. Note, that when the audio synchronization
function is enabled, the 8-bit current control register has no effect.
ALED
ALED driver is enabled when audio synchronization is enabled (EN_SYNC = 1) or when ALED[7:0] control byte
has other than 00h value.
ALED[7:0]
8-Bit IDAC
EN_ALED
Figure 14. ALED Driver
7.3.3.2.1 Adjustment of ALED Driver
Adjustment of the ALED driver current (Register 0Ch) is described in Table 7.
Table 7. ALED Driver Current
ALED[7:0]
DRIVER CURRENT, mA (typical)
0000 0000
0
0000 0001
0.06
0000 0010
0.1
...
...
1111 1101
14.8
1111 1110
14.9
1111 1111
15
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With values other than those in Table 7, the current value can be calculated to be (15 mA / 255) × ALED[7:0],
where ALED[7:0] is value in decimals.
ADC
Figure 15. Principle of LED Connection to ADC
7.3.4 LED Test Interface
All LED pin voltages and boost output voltage in LP55281 can be measured and value can be read through the
SPI/I2C compatible interface. MUX_LED[3:0] bits in the LED test register (address 12h) are used to select one of
the LED outputs or boost output for measurement. The selected output is connected to the internal ADC through
a 55-kΩ resistor divider. The AD conversion is activated by setting the EN_LTEST bit to 1. The first conversion is
ready after 128 µs from this. The result can be read from the ADC output register (address 13h). The device
executes the AD conversions automatically once in every 128 µs period, as long as the EN_LTEST bit is 1.
User can set the preferred DC current level with the LED driver controls. The PWM of the RGB drivers must be
set to 100% — otherwise random variation can appear on results. Note that the 55-kΩ resistor divider causes
small additional current through the LED under measurement.
ADC result can be converted into a voltage value (of the selected pin) by multiplying the ADC result (in decimals)
with 27.345 mV (value of LSB). The calculated voltage value is the voltage between the selected pin and ground.
The internal LDO voltage is used as a reference voltage for the conversion. The accuracy of LDO is ± 3%, which
is defining the overall accuracy. The non-linearity and offset figures are both better than 2LSB.
Table 8. LED Multiplexing (Register 12h)
MUX_LED[3:0]
CONNECTION
0000
R1
0001
G1
0010
B1
0011
R2
0100
G2
0101
B2
0110
R3
0111
G3
1000
B3
1001
R4
1010
G4
1011
B4
1100
ALED
1101
—
1110
1111
20
Boost output
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7.3.4.1 LED Test Procedure
An example of LED test sequence is presented here. Note that user can use incremental write sequence on I2C.
The test sequence consists of the basic setup and measurement phases for all RGB LEDs and boost voltage.
Basic setup phase for the device:
1. Give reset to LP55281 (by power on, NRST pin or write any data to register 60h)
2. Set the preferred value for RED1 (write 3Fh, 7Fh, BFh or FFh to register 00h)
3. Set the preferred value for GREEN1 (write 3Fh, 7Fh, BFh or FFh to register 01h)
4. Set the preferred value for BLUE1 (write 3Fh, 7Fh, BFh or FFh to register 02h)
5. Set the preferred value for RED2 (write 3Fh, 7Fh, BFh or FFh to register 03h)
6. Set the preferred value for GREEN2 (write 3Fh, 7Fh, BFh or FFh to register 04h)
7. Set the preferred value for BLUE2 (write 3Fh, 7Fh, BFh or FFh to register 05h)
8. Set the preferred value for RED3 (write 3Fh, 7Fh, BFh or FFh to register 06h)
9. Set the preferred value for GREEN3 (write 3Fh, 7Fh, BFh or FFh to register 07h)
10. Set the preferred value for BLUE3 (write 3Fh, 7Fh, BFh or FFh to register 08h)
11. Set the preferred value for RED4 (write 3Fh, 7Fh, BFh or FFh to register 09h)
12. Set the preferred value for GREEN4 (write 3Fh, 7Fh, BFh or FFh to register 0Ah)
13. Set the preferred value for BLUE4 (write 3Fh, 7Fh, BFh or FFh to register 0Bh)
14. Set the preferred value for ALED (write 01h - FFh to register 0Ch)
15. Dummy write: 00h to register 0Dh (Only if the incremental write sequence is used)
16. Dummy write: 00h to register 0Eh (Only if the incremental write sequence is used)
17. Set preferred boost voltage (write 00h - FFh to register 0Fh)
18. Set preferred boost frequency (write 00h - 07h to register 10h, PWM frequency can be anything)
19. Enable boost and RGB drivers (write CFh to register 11h)
20. Wait 20 ms for the device and boost start-up
Measurement phase:
1. Enable LED test and select output (write 1xh to register 12h)
2. Wait for 128 µs
3. Read ADC output (read register 13h)
4. Go to step 1 of measurement phase and define next output to be measured as many times as needed
5. Disable LED test (write 00h to register 12h) or give reset to the device (see step 1 in basic setup phase)
7.3.4.2 LED Test Time Estimation
Assuming the maximum clock frequencies used in SPI or I2C-compatible interfaces, Table 9 predicts the overall
test sequence time for the test procedure shown above. This estimation gives the shortest time possible.
Incremental write is assumed with I2C. Reset and LED test disable are not included.
Table 9. LED Test Time
TEST PHASE
TIME (ms)
I2C
SPI
Setup
0.528
0.024
Boost start-up
20
20
14 measurements
4.137
1.831
Total time
24.7
21.9
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7.3.5 7-V Shielding
To shield the LP55281 device from high-input voltages (6 V to 7.2 V), the use of an external 2.8-V LDO is
required. This 2.8-V voltage protects internally the device against high voltage condition. The recommended
connection is shown in the picture below. Internally both logic and analog circuitry works at 2.8-V supply voltage.
Both supply voltage pins should have separate filtering capacitors. TI recommends pulling down the external
LDO voltage when it is disabled in order to minimize the leakage current of the LED outputs.
LBoost
BATTERY
CIN
10 PF
VDD2
2.8V
LDO
2.8V
SW
Digital
supply
voltage
VDD1
VDDA
LDO
CVDDA
CVDD
1 PF
Analog
supply
voltage
100 nF
LP55281
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Figure 16. LP55281 With 7-V Shielding
In cases where high voltage is not an issue, the alternative connection is shown below.
LBoost
BATTERY
+
CIN
CVDD
-
10 PF
100 nF
VDD1
Digital
supply
voltage
VDD2
2.8V
CVDDA
1 PF
SW
VDDA
LDO
Analog
supply
voltage
LP55281
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Figure 17. LP55281 Without 7-V Shielding
22
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7.4 Device Functional Modes
7.4.1 Modes Of Operation
RESET:
In the RESET mode all the internal registers are reset to the default values and the device goes to
STANDBY mode after reset. NSTBY control bit is low after reset by default. Reset is entered
always if Reset Register is written, internal Power On Reset is active, or NRST pin is pulled down
externally. The LP55281 can be reset by writing any data to the Reset Register (address 60H).
Power On Reset (POR) will activate during the device startup or when the supply voltage VDD2 falls
below 1.5 V. Once VDD2 rises above 1.5V, POR inactivates, and the device continues to the
STANDBY mode.
STANDBY: The STANDBY mode is entered if the register bit NSTBY is LOW. This is the low power
consumption mode, when all circuit functions are disabled. Registers can be written in this mode
and the control bits are effective immediately after startup.
STARTUP: When NSTBY bit is written high, the INTERNAL STARTUP SEQUENCE powers up all the needed
internal blocks (VREF, Oscillator, etc.). To ensure the correct oscillator initialization, a 10 ms delay
is generated by the internal state-machine. If the device temperature rises too high, the Thermal
Shutdown (TSD) disables the device operation and STARTUP mode is entered until no thermal
shutdown is present.
BOOST STARTUP: Soft start for boost output is generated in the BOOST STARTUP mode. The boost output is
raised in PWM mode during the 10 ms delay generated by the state-machine. The Boost startup is
entered from Internal Startup Sequence if EN_BOOST is HIGH or from Normal mode when
EN_BOOST is written HIGH. During the 10 ms Boost Startup time all LED outputs are switched off
to ensure smooth startup.
NORMAL:
During NORMAL mode the user controls the device using the Control Registers. The registers can
be written in any sequence and any number of bits can be altered in a register in one write.
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Device Functional Modes (continued)
RESET
POR = L
Reset Register write
or POR = H or NRST = L
STANDBY
NSTBY = H
NSTBY = L
INTERNAL
STARTUP
SEQUENCE
V REF = 95% OK*
TSD = H
~10 ms Delay
EN_BOOST = H*
EN_BOOST = L*
BOOST STARTUP
EN_BOOST
rising edge*
~10 ms Delay
NORMAL MODE
24
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* TSD = L
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7.5 Programming
The LP55281 supports two different interface modes:
• SPI Interface (4-wire, serial)
• I2C Compatible Serial Bus Interface
User can define the serial interface by IF_SEL pin. If IF_SEL = 0, I2C mode is selected.
7.5.1 SPI Interface
The LP55281 is compatible with SPI serial-bus specification and it operates as a slave. The transmission
consists of 16-bit write and read cycles. One cycle consists of a 7 address bits, 1 read/write (RW) bit and 8 data
bits. RW bit high state defines a write cycle and low a read cycle. SO output is normally in high-impedance state
and it is active only when data is sent out during a read cycle. A pullup resistor may be needed in SO line if a
floating logic signal can cause unintended current consumption in the input circuits where SO is connected. The
Address and Data are transmitted MSB first. The slave select signal (SS) must be low during the cycle
transmission. SS resets the interface when high and it has to be taken high between successive cycles. Data is
clocked in on the rising edge of the clock signal (SCK), while data is clocked out on the falling edge of SCK.
SS
SCK
SI
A6
A5
A4
A3
A2
A1
A0
1
R/W
D7
D6
D5
D4
D3
D2
D1
D0
D2
D1
D0
SO
Figure 18. SPI Write Cycle
SS
SCK
SI
A6
A5
A4
A3
A2
A1
A0
R/W
0
Don't Care
D7
SO
D6
D5
D4
D3
Figure 19. SPI Read Cycle
7.5.2 I2C Compatible Serial Bus Interface
7.5.2.1 Interface Bus Overview
The I2C compatible synchronous serial interface provides access to the programmable functions and registers on
the device. This protocol uses a two-wire interface for bidirectional communications between the devices
connected to the bus. The two interface lines are the serial data line (SDA) and the serial clock line (SCL). These
lines should be connected to a positive supply, via a pullup resistor and remain HIGH even when the bus is idle.
For every device on the bus is assigned a unique address and it acts as a master or a slave, depending on
whether it generates or receives the SCL. When LP55281 is connected in parallel with other I2C compatible
devices, the LP55281 supply voltages VDD1, VDD2 and VDDIO must be active. Supplies are required to make sure
that the LP55281 does not disturb the SDA and SCL lines.
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Programming (continued)
7.5.2.2 Data Transactions
One data bit is transferred during each clock pulse. Data is sampled during the high state of the SCL.
Consequently, throughout the clock's high period, the data should remain stable. Any changes on the SDA line
during the high states of the SCL and in the middle of the transaction, aborts the current transaction. New data
should be sent during the low SCL state. This protocol permits a single data line to transfer both
command/control information and data using the synchronous serial clock.
SCL
SDA
data
change
allowed
data
valid
data
valid
data
change
allowed
data
change
allowed
Figure 20. Data Validity
Each data transaction is composed of a start condition, a number of byte transfers (set by the software) and a
stop condition to terminate the transaction. Every byte written to the SDA bus must be 8 bits long and is
transferred with the most significant bit first. After each byte, an acknowledge signal must follow. The following
sections provide further details of this process.
SCL
Data Output
by Receiver
Data Output
by Transmitter
Transmitter Stays off the
Bus During the
Acknowledge Clock
Acknowledge Signal
from Receiver
1
2
3...6
7
8
9
S
Start
Condition
Figure 21. Acknowledge Signal
The Master device on the bus always generates the start and stop conditions (control codes). After a start
condition is generated, the bus is considered busy and it retains this status until a certain time after a stop
condition is generated. A high-to-low transition of the data line (SDA), while the clock (SCL) is high, indicates a
Start Condition. A low-to-high transition of the SDA line, while the SCL is high, indicates a stop condition.
SDA
SCL
S
P
START condition
STOP condition
Figure 22. Start And Stop Conditions
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Programming (continued)
In addition to the first start condition, a repeated start condition can be generated in the middle of a transaction.
This allows another device to be accessed or a register read cycle.
7.5.2.3 Acknowledge Cycle
The acknowledge cycle consists of two signals: the acknowledge clock pulse the master sends with each byte
transferred, and the acknowledge signal sent by the receiving device.
The master generates the acknowledge clock pulse on the ninth clock pulse of the byte transfer. The transmitter
releases the SDA line (permits it to go high) to allow the receiver to send the acknowledge signal. The receiver
must pull down the SDA line during the acknowledge clock pulse and ensure that SDA remains low during the
high period of the clock pulse, thus signaling the correct reception of the last data byte and its readiness to
receive the next byte.
7.5.2.4 Acknowledge After Every Byte Rule
The master generates an acknowledge clock pulse after each byte transfer. The receiver sends an acknowledge
signal after every byte received.
There is one exception to theacknowledge after every byte rule. When the master is the receiver, it must indicate
to the transmitter an end of data by not-acknowledging (negative acknowledge) the last byte clocked out of the
slave. This negative acknowledge still includes the acknowledge clock pulse (generated by the master), but the
SDA line is not pulled down.
7.5.2.5 Addressing Transfer Formats
Each device on the bus has a unique slave address. The LP55281 operates as a slave device with 7-bit address.
LP55281 I2C address is pin selectable from two different choices. The LP55281 address is 4Ch (SI/A0 = 0) or
4Dh (SI/A0 = 1) as selected with SI/A0 pin. If eighth bit is used for programming, the 8th bit is 1 for read and 0 for
write.
Before any data is transmitted, the master transmits the address of the slave being addressed. The slave device
should send an acknowledge signal on the SDA line, once it recognizes its address.
The slave address is the first seven bits after a start condition. The direction of the data transfer (R/W) depends
on the bit sent after the slave address (the eighth bit).
When the slave address is sent, each device in the system compares this slave address with its own. If there is a
match, the device considers itself addressed and sends an acknowledge signal. Depending upon the state of the
R/W bit (1 for read, 0 for write), the device acts as a transmitter or a receiver.
MSB
LSB
ADR6
bit7
ADR5
bit6
ADR4
bit5
ADR3
bit4
ADR2
bit3
ADR1
bit2
ADR0
bit1
1
0
1
0
1
0
0
R/W
bit0
I2 C SLAVE address (chip address)
Figure 23. I2C Device Address
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Programming (continued)
7.5.2.6 Control Register Write Cycle
• Master device generates start condition
• Master device sends slave address (7 bits) and the data direction bit (r/w=0).
• Slave device sends acknowledge signal if the slave address is correct.
• Master sends control register address (8 bits).
• Slave sends acknowledge signal.
• Master sends data byte to be written to the addressed register.
• Slave sends acknowledge signal.
• If master will send further data bytes, the control register address will be incremented by one after
acknowledge signal
• Write cycle ends when the master creates stop condition.
7.5.2.7 Control Register Read Cycle
• Master device generates a start condition.
• Master device sends slave address (7 bits) and the data direction bit (r/w=0).
• Slave device sends acknowledge signal if the slave address is correct.
• Master sends control register address (8 bits).
• Slave sends acknowledge signal.
• Master device generates repeated start condition.
• Master sends the slave address (7 bits) and the data direction bit (r/w=1).
• Slave sends acknowledge signal if the slave address is correct.
• Slave sends data byte from addressed register.
• If the master device sends acknowledge signal, the control register address will be incremented by one. Slave
device sends data byte from addressed register.
• Read cycle ends when the master does not generate acknowledge signal after data byte and generates stop
condition.
ADDRESS MODE
Data Read
[Ack]
[Ack]
[Ack]
[Register Data]
...additional reads from subsequent register address possible
Data Write
[Ack]
[Ack]
[Ack]
...additional writes to subsequent register address possible
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< > Data from master, [ ] data from slave
ack from slave
msb Chip Address lsb
start
w
ack from slave data from slave ack/nack from
master
ack from slave repeated start
msb Register Add lsb
rs
msb Chip Address lsb
rs
Id = 4Ch
r
msb
DATA
lsb
stop
SCL
SDA
start
Id = 4Ch
w ack
addr = h00
ack
r ack
Address 00h data
ack stop
Figure 24. Register READ Format
When a READ function is to be accomplished, a WRITE function must precede the READ function, as shown in
the Read Cycle waveform.
ack from slave
ack from slave
start
msb Chip Address lsb
w
ack
w
ack
msb Register Add lsb
ack
msb
ack from slave
DATA
lsb
ack
stop
ack
stop
SCL
SDA
start
id = 4Ch
addr = 02H
ack
address 02H data
Figure 25. Register WRITE Format
•
•
•
•
•
w = write (SDA = 0)
r = read (SDA = 1)
ack = acknowledge (SDA pulled down by either master or slave)
rs = repeated start
id = 7-bit device address
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7.6 Register Maps
Following table summarizes the registers and their default values
Address
Register
00h
RED1
D7
GREEN1
02h
BLUE1
03h
RED2
04h
GREEN2
GREEN3
08h
BLUE3
09h
RED4
0Ch
ALED
0Dh
Audio Sync
CTRL1
0Eh
Audio Sync
CTRL2
0
0
0
0
0
Enables
0
0
0
0
0
0
0
0
0
0
0
(1)
30
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
R3_PWM[5:0]
0
0
0
0
0
G3_PWM[5:0]
0
0
0
0
0
B3_PWM[5:0]
0
0
0
0
0
R4_PWM[5:0]
0
0
0
0
0
0
0
0
G4_PWM[5:0]
0
0
B4_PWM[5:0]
0
0
0
0
0
0
0
0
0
0
0
0
DC_FREQ
EN_AGC
EN_SYNC
0
0
0
SPEED_CTRL[1:0]
1
1
0
0
1
1
0
0
1
1
Boost[7:0]
NSTBY
0
1
1
FPWM1
FPWM0
0
0
EN_BOOST EN_AUTOL
OAD
0
FRQ_SEL[2:0]
1
1
1
EN_RGB4
EN_RGB3
EN_RGB2
EN_RGB1
0
0
0
0
0
0
0
EN_LTEST
0
60h
0
B2_PWM[5:0]
0
LED Test
13h (1)
0
THRESHOLD[3:0]
0
12h
0
G2_PWM[5:0]
GAIN_SEL[2:0]
0
11h
0
R2_PWM[5:0]
Boost Output
Frequency
Selections
0
ALED[7:0]
0
10h
D0
B1_PWM[5:0]
B4 - IPLS[7:6]
0
0Fh
0
G4 - IPLS[7:6]
0
BLUE4
0
R4 - IPLS[7:6]
0
0Bh
0
B3 - IPLS[7:6]
0
GREEN4
0
G3 - IPLS[7:6]
0
D1
G1_PWM[5:0]
R3 - IPLS[7:6]
0
0Ah
0
B2 - IPLS[7:6]
0
07h
0
G2 - IPLS[7:6]
0
RED3
0
D2
R1_PWM[5:0]
0
R2 - IPLS[7:6]
0
06h
D3
B1 - IPLS[7:6]
0
BLUE2
D4
G1 - IPLS[7:6]
0
05h
D5
R1 - IPLS[7:6]
0
01h
D6
ADC Output
MUX_LED[3:0]
0
0
DATA[7:0]
0
0
0
0
0
0
0
0
r/o
r/o
r/o
r/o
r/o
r/o
r/o
r/o
Reset
Writing any data to Reset Register resets LP55281
r/o = read-only
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LP55281 quadruple RGB driver with integrated boost converter provides a complete solution for driving up to
12 LEDs via either I2C or SPI interface.
8.2 Typical Application
IMAX = 300...400 mA
Lboost
+
CIN
CVDD
-
10 PF
100 nF
CVDDA
1 éF
BATTERY
CREF
VOUT = 4...5.3V
SW
VDD1
VDD2
VDDA
FB
B1
IRGB
MCU
CVDDIO
RGB2
IRT
R2
SO
SI/A0
SCK/SCL
G2
SS/SDA
NRST
VDDIO
B2
LP55281
RGB3
R3
G3
IF_SEL
100 nF
RGB1
G1
VREF
RRT
10 PF
R1
100 nF
RRGB
COUT
D1
4.7 PH
B3
RGB4
R4
G4
B4
ASE1
ALED
ASE2
AUDIO
INPUTS
GNDs
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Figure 26. LP55281 Typical Application
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Typical Application (continued)
8.2.1 Design Requirements
For typical LED-driver applications, use the parameters listed in Table 10.
Table 10. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Input voltage
3V
Output voltage
5V
SW pin current limit
550 mA (minimum)
Efficiency
75%
8.2.2 Detailed Design Procedure
The output current can be approximated by using this formula: IOUT = (VIN × ISW_MAX × efficiency) / VOUT.
Example: 3 V × 550 mA × 0.75 / 5 V = 248 mA
8.2.2.1 Recommended External Components
8.2.2.1.1 Output Capacitor, COUT
The output capacitor COUT directly affects the magnitude of the output ripple voltage. In general, the higher the
value of COUT, the lower the output ripple magnitude. Multilayer ceramic capacitors with low ESR are the best
choice. At the lighter loads, the low ESR ceramics offer a much lower VOUT ripple than the higher ESR tantalums
of the same value. At the higher loads, the ceramics offer a slightly lower VOUT ripple magnitude than the
tantalums of the same value. However, the dv/dt of the VOUT ripple with the ceramics is much lower than the
tantalums under all load conditions. Capacitor voltage rating must be sufficient, TI recommends 10 V or greater.
Some ceramic capacitors, especially those in small packages, exhibit a strong capacitance reduction with the
increased applied voltage. The capacitance value can fall to below half of the nominal capacitance. Output
capacitance that is too low increase the noise, and it can make the boost converter unstable.
8.2.2.1.2 List Of Recommended External Components
PARAMETER
VALUE
UNIT
TYPE
CVDD1
C between VDD1 and GND
100
nF
Ceramic, X7R/X5R
CVDD2
C between VDD2 and GND
100
nF
Ceramic, X7R/X5R
CVDDIO
C between VDDIO and GND
100
nF
Ceramic, X7R/X5R
CVDDA
C between VDDA and GND
1
µF
Ceramic, X7R/X5R
COUT
C between FB and GND
10
µF
Ceramic, X7R/X5R
CIN
C between battery voltage and GND
10
µF
Ceramic, X7R/X5R
LBOOST
L between SW and VBAT at 2 MHz
4.7
µH
Shielded, low ESR, ISAT 1A
CVREF
C between VREF and GND
100
nF
Ceramic, X7R
CVDDIO
C between VDDIO and GND
100
nF
Ceramic, X7R
RRGB
R between IRGB and GND
8.2
kΩ
±1%
RRT
R between IRT and GND
82
kΩ
±1%
D1
Rectifying Diode (Vf at maxload)
0.3
V
Schottky diode
CASE
C between Audio input and ASEx
100
nF
Ceramic, X7R/X5R
LEDs
User defined
8.2.2.1.3 Input Capacitor, CIN
The input capacitor CIN directly affects the magnitude of the input ripple voltage and to a lesser degree the VOUT
ripple. A higher value CIN gives a lower VIN ripple. Capacitor voltage rating must be sufficient, TI recommends 10
V or greater.
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8.2.2.1.4 Output Diode, D1
A Schottky diode must be used for the output diode. To maintain high efficiency the average current rating of the
Schottky diode must be larger than the peak inductor current (1 A). Schottky diodes with a low forward drop and
fast switching speeds are ideal for increasing efficiency in portable applications. Choose a reverse breakdown of
the Schottky diode larger than the output voltage. Do not use ordinary rectifier diodes, since slow switching
speeds and long recovery times cause the efficiency and the load regulation to suffer.
8.2.2.1.5 Inductor, L
The high switching frequency of the LP55281 device enables the use of the small surface mount inductor. A 4.7µH shielded inductor is suggested for 2-MHz operation, use 10 µH at 1 MHz. The inductor should have a
saturation current rating higher than the peak current it will experience during circuit operation (approximately 1
A). Less than 300-mΩ ESR is suggested for high efficiency. Open core inductors cause flux linkage with circuit
components and interfere with the normal operation of the circuit. This should be avoided. For high efficiency,
choose an inductor with a high frequency core material such as ferrite to reduce the core losses. To minimize
radiated noise, use a toroid, pot core or shielded core inductor. TI recommends inductors LPS3015 and LPS4012
from Coilcraft and VLF4012 from TDK.
VOLTAGE
ILOAD = 50 mA
VIN = 3.0V TO 3.6V
VIN = 1V/DIV
VOUT = 5V (10 mV/DIV)
(5V/DIV)
VSWITCH
ICOIL
100 mA
AVERAGE
(100 mA/DIV)
VOUT = 5.0V
(20 mV/DIV)
8.2.3 Application Curves
TIME (200 ns/DIV)
TIME (100 és/DIV)
Figure 27. Boost Typical Waveforms With 100 mA Load
Figure 28. Boost Line Regulation
OUTPUT VOLTAGE (V)
5.1
5.1
4.8
4.8
4.4
4.4
VOUT TARGET VALUE = 5V
VIN = 3.6V
4.1
4.1
3.7
3.7
3.4
3.4
0.0
100.0
200.0 300.0
TIME (és)
400.0
500.0
50 - 100 mA
Figure 29. Boost Start-up With No Load
Figure 30. Boost Load Regulation
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90.0
90.0
EFFICIENCY (%)
74.0
74.0
58.0
58.0
Autoload ON
42.0
42.0
Autoload OFF
26.0
26.0
10.0
10.0
1.0
7.8
14.6
21.4
28.2
35.0
LOAD CURRENT (mA)
Figure 31. Efficiency at Low Load vs Autoload
8.3 Initialization Set Up Example
The following table gives an example initialization sequence to illustrate the various LED and Boost configuration
options. Not every feature of the LP55281 is configured in this example.
Table 11. Initialization Example
ADDRESS
DATA
REGISTER
COMMENT
60h
00h
RESET
Execute software reset to initialize LP55281
00h
3Fh
RED 1
IPLS = 0 (25% IRGB), PWM = 100%
01h
5Fh
GREEN1
IPLS = 1 (50% IRGB), PWM = 50%
02h
90h
BLUE1
IPLS = 2 (75% IRGB), PWM = 25.4%
03h
C8h
RED 2
IPLS = 3 (100% IRGB), PWM = 12.7%
04h
1Fh
GREEN2
IPLS = 0 (25% IRGB), PWM = 50%
05h
10h
BLUE2
IPLS = 0 (25% IRGB), PWM = 25.4%
06h
07h
RED 3
IPLS = 0 (25% IRGB), PWM = 11.1%
07h
03h
GREEN3
IPLS = 0 (25% IRGB), PWM = 4.8%
08h
01h
BLUE3
IPLS = 0 (25% IRGB), PWM = 1.6%
09h
0h
RED 4
IPLS = 0 (25% IRGB), PWM = 0%
0Ah
0h
GREEN4
IPLS = 0 (25% IRGB), PWM = 0%
0Bh
0h
BLUE4
IPLS = 0 (25% IRGB), PWM = 0%
0Fh
0Fh
Boost Output
Boost output voltage set to 4.7V
10h
07h
Frequency
Selections
PWM frequency (FPWM[1:0] = 0, 9.92 kHz), Boost SW frequency =
2 MHz
11h
CFh
Enables
NSTBY, EN_BOOST, EN_RGB4, EN_RGB3, EN_RGB2, EN_RGB1
= 1 (exit standby state, enable boost and rgb drivers)
9 Power Supply Recommendations
The LP55281 is designed to operate from an input supply range of 2.7 V to 5.5 V. This input supply must be well
regulated and able to provide the peak current required by the LED configuration without voltage drop under load
transients (enable on/off). The resistance of the input supply rail should be low enough such that the input
current transient does not cause the LP55281 supply voltage to droop more than 5%. Additional bulk decoupling
located close to the input capacitor (CIN) may be required to minimize the impact of the input supply rail
resistance.
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10 Layout
10.1 Layout Guidelines
The inductive boost converter of the LP55281 regulates a switched voltage at the SW pin, and a step current (up
to ICL) through the Schottky diode and output capacitor each switching cycle. The switching voltage can create
interference into nearby nodes due to electric field coupling (I = CdV/dt). The large step current through the diode
and the output capacitor can cause a large voltage spike at the SW pin and the OUT pin due to parasitic
inductance in the step current conducting path (V = Ldi/dt). Board layout guidelines are geared towards
minimizing this electric field coupling and conducted noise.
The following list details the main (layout sensitive) areas of the LP55281 device's inductive boost converter in
order of decreasing importance:
• Output Capacitor
– Schottky cathode to COUT+
– COUT– to GND
• Schottky Diode
– SW pin to Schottky anode
– Schottky Cathode to COUT+
• Inductor
– SW Node PCB capacitance to other traces
• Input Capacitor
– CIN+ to IN pin
10.1.1 Boost Output Capacitor Placement
Because the output capacitor is in the path of the inductor current discharge path it detects a high-current step
from 0 to IPEAK each time the switch turns off and the Schottky diode turns on. Any parasitic inductance (LP_)
along this series path from the cathode of the diode through COUT and back into the GND pin of the LP55281
device GND pin contributes to voltage spikes (VSPIKE = LP_ × di/dt) at SW and FB. These spikes can
potentially over-voltage the SW pin, or feed through to GND. To avoid this, COUT+ must be connected as close
as possible to the cathode of the Schottky diode, and COUT− must be connected as close the the GND pin of
the device as possible. The best placement for COUT is on the same layer as the LP55281 in order to avoid any
vias that can add excessive series inductance.
10.1.2 Schottky Diode Placement
In the boost circuit of the LP55281 device the Schottky diode is in the path of the inductor current discharge. As
a result the Schottky diode sees a high-current step from 0 to IPEAK each time the switch turns off and the diode
turns on. Any parasitic inductance (LP) in series with the diode causes a voltage spike (VSPIKE = LP × di/dt) at
SW and OUT. This can potentially over-voltage the SW pin, or feed through to VOUT and through the output
capacitor and into GND. Connecting the anode of the diode as close as possible to the SW pin and the cathode
of the diode as close as possible to COUT and reduces the parasitic inductance and minimize these voltage
spikes.
10.1.3 Inductor Placement
The node where the inductor connects to the LP55281 device's SW pin has 2 concerns. First, the switched
voltage (0 to VOUT + VF_SCHOTTKY) appears on this node every switching cycle. This switched voltage can be
capacitively coupled into nearby nodes. Second, there is a relatively large current (input current) on the traces
connecting the input supply to the inductor and connecting the inductor to the SW bump. Any resistance in this
path can cause voltage drops that can negatively affect efficiency and reduce the input operating voltage range.
To reduce the capacitive coupling of the signal on SW into nearby traces, the SW bump-to-inductor connection
must be minimized in area. This limits the PCB capacitance from SW to other traces. Additionally, high
impedance nodes that are more susceptible to electric field coupling need to be routed away from SW and not
directly adjacent or beneath. This is especially true for sensitive analog signals (ASE1, ASE2, FB, IRT, IRGB,
VREF). A GND plane placed directly below SW dramatically reduces the capacitance from SW into nearby
traces. Lastly, limit the trace resistance of the VIN to inductor connection and from the inductor to SW
connection, by use of short, wide traces.
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LP55281
SNVS458D – JUNE 2007 – REVISED OCTOBER 2016
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Layout Guidelines (continued)
10.1.4 Boost Input Capacitor Placement
Close placement of the input capacitor to the IN pin and to the GND pin is critical because any series inductance
between IN and CIN+ or CIN− and GND can create voltage spikes that could appear on the VIN supply line and
in the GND plane. Close placement of the input bypass capacitor at the input side of the inductor is also critical.
10.2 Layout Example
Short wide paths on all high di/dt nodes
(SW, GND_SW, VOUT).
Keep current loops as short as possible.
Route sensitive FB node away
from high dv/dt nodes and keep
as short as possible.
VOUT
COUT
B1
G1
R1
B3
FB
SW
GND_
RGB1
IRGB
SS/
SDA
G3
R3
GND_
SW
R2
SO
SI/A0
ASE2
GND
GND_
RGB2
G2
SCK/
SCL
VDDI
O
VDD1
R4
NRST
B2
IF_
SEL
IRT
ASE1
G4
ALED
VDD2
VDDA
VREF
GNDA
B4
GND
L1
GND
CIN
VDD
TOP Layer GND plane connecting
SW_GND to COUT and CIN.
Connect to system ground using as
many vias as possible.
Copyright © 2016, Texas Instruments Incorporated
Figure 32. LP55281 Layout
36
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LP55281
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SNVS458D – JUNE 2007 – REVISED OCTOBER 2016
11 Device and Documentation Support
11.1 Device Support
11.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
11.2 Related Documentation
For additional information, see the following:
• AN-1112 DSBGA Wafer Level Chip Scale Package
• AN-1412 Micro SMDxt Wafer Level Chip Scale Package
11.3 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
11.4 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.5 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.6 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
11.7 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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Product Folder Links: LP55281
37
PACKAGE OPTION ADDENDUM
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10-May-2022
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
LP55281TL/NOPB
ACTIVE
DSBGA
YZR
36
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-30 to 85
D56B
Samples
LP55281TLX/NOPB
ACTIVE
DSBGA
YZR
36
1000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-30 to 85
D56B
Samples
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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