TPS60255
www.ti.com
SLVS825 – MARCH 2008
HIGH EFFICIENCY CHARGE PUMP FOR 7 WLEDs DRIVER WITH 1 WIRE INTERFACE
FEATURES
1
•
•
•
•
•
2
•
•
•
•
•
•
2.7 V to 6.0 V Input Voltage Range
1× and 1.5× Charge Pump
Auto Switching Between 1× and 1.5× Modes
750 kHz Charge Pump Frequency
Seven Individually-regulated WLED
Current Sinks
Single- Wire Interface for Dimming and
ON/OFF Control
25 mA max LED Current for Six Current Sinks
One 80 mA Current Sink
Open WLED Detection
Built-in Soft Start and Current Limit
16-pin, 3 mm × 3 mm QFN Package
APPLICATIONS
•
•
•
Cellular Phones
Portable Navigation Displays
Multi-display Handheld Devices
DESCRIPTION
The TPS60255 is a high-efficiency, constant
frequency charge pump DC/DC converter that uses
1× and 1.5× conversion to maximize efficiency for the
input voltage range. By using adaptive 1×/1.5×
charge-pump modes and very low dropout current
regulators, the TPS60255 achieves high efficiency for
the entire one-cell lithium battery range. The
protection features include soft start, over-current
limit, thermal shut down, and over-voltage detection.
The device automatically detects and removes
unused current sinks from the control loop.
This device drives six 25 mA current sinks and one
80 mA current sink. These current regulators are
programmed by three independent brightness
registers and five ON/OFF bits using a single-wire
interface (EasyScale™).
This offers
flexible
applications for a variety of lighting control in portable
devices.
AUX
100
C2
1 mF
C3
1 mF
GC
GA4
GA3
GA2
C2+
GA1
C2-
GB2
C1+
GB1
VIN
ENA
Efficiency − %
GND
C1-
VIN = Sweep Down
4 LEDs: GA1, GA2, GA3, and GA4
* LED: NSSW100CT (NICHIA)
90
Back Light
for
LCD Display
80
70
60
ILED = 15.3 mA
50
IF
ILED = 25.2 mA
ILED = 2.1 mA
VOUT
C4
2.2 mF
40
2.9
C1
4.7 mF
Enable/
Disable
3.4
Interface Using
EasyScale
Figure 1. Typical Application
3.9
4.4
4.9
VIN − Input Voltage − V
G001
Figure 2. Characteristic Curve
a
ORDERING INFORMATION (1)
(1)
PART
NUMBER
PACKAGE
MARKING
PACKAGE
TA
TPS60255RTE
BUP
16-Pin 3 mm × 3 mm QFN (RTE)
–40°C to +85°C
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
EasyScale is a trademark of Texas Instruments.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2008, Texas Instruments Incorporated
TPS60255
www.ti.com
SLVS825 – MARCH 2008
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted) (1)
VI
Input voltage range (all pins)
HBM ESD Rating
2
kV
500
V
MM ESD Rating (4)
200
V
–40 to 85
°C
150
°C
–55 to 150
°C
Operating temperature range
Maximum operating junction temperature
TST
Storage temperature
(3)
(4)
V
CDM ESD Rating (3)
TJ
(2)
UNIT
(2)
TA
(1)
VALUE
–0.3 to 7
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other conditions beyond those indicated under recommended operating
conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
The Human body model (HBM) is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
The testing is done according JEDEC EIA/JESD22-A114.
Charged Device Model
Machine Model (MM) is a 200 pF capacitor discharged through a 500 nH inductor with no series resistor into each pin. The testing is
done according JEDEC EIA/JESD22-A115.
DISSIPATION RATINGS
PACKAGE
THERMAL
RESISTANCE, RθJA
TA ≤ 25°C POWER
RATING
DERATING FACTOR
ABOVE TA = 25°C
TA = 85°C POWER
RATING
QFN 3×3 RTE
48.7°C/W
2.05 W
1.13 W
0.821 W
RECOMMENDED OPERATING CONDITIONS
MIN
NOM
2.7
MAX
6.0
UNIT
VI
Input voltage range
IO(max)
Maximum output current
C1
Input capacitor
C4
Output capacitor
C2, C3
Flying capacitor
TA
Operating ambient temperature
–40
85
°C
TJ
Operating junction temperature
–40
125
°C
MAX
UNIT
2.2
V
230
mA
1.0
µF
4.7
µF
1.0
µF
ELECTRICAL CHARACTERISTICS
VI = 3.5 V, TA = –40°C to 85°C, typical values are at TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
SUPPLY VOLTAGE
VIN
Input voltage range
IQ
Operating quiescent current
2.7
1.5X Mode, IO = 61 mA
1X mode, IO = 61 mA
1X mode, IO = 100 µA
ISD
Shutdown current
EN = GND
VUVLO1
UVLO threshold voltage 1 (1)
VIN falling
VHYS_UVLO1
UVLO 1 hysteresis
VIN rising
VUVLO2
UVLO threshold voltage 2 (2)
VIN falling
(1)
(2)
2
6.0
2.1
2.3
mA
3.2
mA
68
µA
1
µA
2.5
200
1.2
1.3
V
8
V
mV
1.45
V
Shut down charge pump and power stage, but keep register values.
Shut down completely and come up with all zeros after device restart.
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
TPS60255
www.ti.com
SLVS825 – MARCH 2008
ELECTRICAL CHARACTERISTICS (continued)
VI = 3.5 V, TA = –40°C to 85°C, typical values are at TA = 25°C (unless otherwise noted)
PARAMETER
VENA_H
Enable high threshold voltage
VENA_L
Enable low threshold voltage
TS
Soft start time (3)
TEST CONDITIONS
MIN
TYP
1.5
MAX
VIN
0.4
0.5
UNIT
V
V
ms
CHARGE PUMP
VOUT
Overvoltage limit
Fs
Switching frequency
RO
Open loop output impedance
6.6
625
V
750
875
1× Mode, (VIN –VO) ÷ IO
1.0
1.2
1.5× Mode, (VIN × 1.5 – VO) ÷ IO
VIN = 3.1 V, IO = 230 mA
2.8
3.5
kHz
Ω
CURRENT SINK
Km_GB
Current matching of Group B at light load
condition (4)
TA = 0° to 40°C, IGB_LED = 100 µA × 2
3.1 V ≤ VIN ≤ 4.2 V, VDX= 0.4 V
±0.1
±2
%
Km
LED to LED current matching of Group A
and B (6 LEDs) (4)
IGAB_LED = 15.3 mA × 6
3.1V ≤ VIN ≤ 4.2 V
±0.1
±5
%
Ka
Current accuracy
IG_AB_M
Maximum LED current of
GA1-4 and GB1-2
VGX = 0.2 V
IGC_M
Maximum LED current of GC
VGX = 0.2 V
VDropOut
LED Drop out voltage
See table note
VTH_GU
1× Mode to 1.5× mode transition
threshold voltage (6)
VGX falling, measured on the lowest
VGX , IO = 61 mA
VTH_GD
1.5× mode to 1× mode
Transition threshold voltage
Measured as VIN-(Vout-VGX_MIN)
IO = 61 mA
ILED = 15.3 mA
±10
ILED = 1.0 mA, TA = 25°C
±15
21.5
25.2
28.9
80
(5)
520
%
mA
mA
60
100
mV
105
120
mV
550
590
mV
INTERFACE TIMING
tStart
Start time
tH_LB
High Time Low Bit,
logic 0 detection
Signal level on IF pin is > 1.2 V
tL_LB
Low Time Low Bit,
logic 0 detection
tL_HB
µs
3.5
3.5
300
µs
Signal level on IF pin < 0.4V
2 × tH_LB
600
µs
Low Time High Bit, logic 1 detection
Signal level on IF pin < 0.4V
3.5
300
µs
tH_HB
High Time High Bit,
logic 1 detection
Signal level on IF pin is > 1.2 V
2 × tL_HB
600
µs
tEOS
End of Stream
tEOS
3.5
600
µs
tACKN
Duration of Acknowledge Condition (IF
line pulled low by the device)
VIN 2.7 V to 6 V
600
750
µs
tvalACK
Acknowledge Valid Time
3.5
µs
(3)
(4)
(5)
(6)
Measurement Condition: From enabling the LED driver to 90% output voltage after VIN is already up.
LED current matching is defined as: |(I - IAVG)| max / IAVG
Dropout Voltage is defined as VGX (LED cathode) to GND voltage at which current into the LED drops 10% from the LED current at
VGX = 0.2 V.
As VIN drops, VGX eventually falls below the switchover threshold of 100 mV, and TPS60255 switches to 1.5× mode. See the Operating
Principle section for details about the mode transition thresholds.
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
3
TPS60255
www.ti.com
SLVS825 – MARCH 2008
PIN ASSIGNMENTS
QFN 16-PIN RTE
3 mm X 3 mm
(TOP VIEW)
GND GC GA4 GA3
12
11
10
9
8
GA2
C2+ 14
7
GA1
C2-
6
GB2
5
GB1
C1-
13
15
C1+ 16
1
2
3
VOUT VIN ENA
4
IF
TERMINAL FUNCTIONS
TERMINAL
I/O
DESCRIPTION
1
O
Connect the output capacitor and the anode of the white LEDs to this pin
2
I
Supply voltage input
ENA
3
I
Hardware Enable/Disable Pin (High = Enable)
IF
4
I
Single wire interface for on/off and brightness control.
GB1
5
I
Current sink input. Connect the cathode of the white LED to this pin.
GB2
6
I
Current sink input. Connect the cathode of the white LED to this pin.
GA1
7
I
Current sink input. Connect the cathode of the white LED to this pin.
GA2
8
I
Current sink input. Connect the cathode of the white LED to this pin.
GA3
9
I
Current sink input. Connect the cathode of the white LED to this pin.
GA4
10
I
Current sink input. Connect the cathode of the white LED to this pin.
GC
11
I
Current sink input. Connect the cathode of the white LED to this pin.
GND
12
–
Ground
C1–
13
–
Connect to the flying capacitor C1
C2+
14
–
Connect to the flying capacitor C2
C2–
15
–
Connect to the flying capacitor C2
C1+
16
–
Connect to the flying capacitor C1
NAME
NO.
VOUT
VIN
4
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
TPS60255
www.ti.com
SLVS825 – MARCH 2008
FUNCTIONAL BLOCK DIAGRAM
VIN
2
C1+
C2–
C2+
C1–
VOUT
GA4
GA3
GA2
GA1
16
15
14
13
1
10
9
8
7
1´,1.5´ CHARGE PUMP
GEAR
CONTROL
EN_GA4
6
GB2
5
GB1
11
GC
12
GND
EN_GA1~GA3
5
GroupA Dimming
EN_GB1
EasyScale
Interface
EN_GB2
5
GroupB Dimming
EN_GC
2
GroupC Dimming
IF
4
BIAS, TEST, and MONITORING
3
ENA
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
5
TPS60255
www.ti.com
SLVS825 – MARCH 2008
TYPICAL CHARACTERISTICS
Table of Characteristic Graphs
Title
Description
Figure
Load efficiency
Efficiency vs Input Voltage, main LED current = 2.1 mA, 15.3 mA, and 25.2mA
Figure 3
Input Current
Input Current vs Input voltage, main LED current = 2.1 mA, 15.3 mA, and 25.2 mA
Figure 4
Shut down current
Shut Down Current vs Input voltage
Figure 5
Output Accuracy
Output Current Accuracy vs Temperature, main LED current = 15.3 mA
Figure 6
Output Impedance
Switch Resistance vs. Temperature, 1X mode, IO = 230 mA
Figure 7
Output Impedance
Switch Resistance vs. Temperature, 1.5X mode, IO = 230 mA
Figure 8
1× → 1.5× Mode Transition Up
1.5× → 1× Mode Transition down
Output Voltage vs Input Voltage, main LED current = 15.3 mA
Figure 9
Normal Operation (1× mode)
Input Voltage, Input Current, GA1 Current, VIN = 4.0 V,
LED current : GA1 = GA2 = GA3 = GA4 = GB1 = GB2 = 25.2 mA
Figure 11
Open Lamp Detection (1× mode)
Input Voltage, Input Current, GA1 Current, VIN = 4.0 V,
LED current : GA1 = GA2 = GA3 = GB1 = GB2 = 25.2 mA (GA4 is open)
Figure 12
EFFICIENCY
vs
INPUT VOLTAGE
INPUT CURRENT
vs
INPUT VOLTAGE
100
0.18
VIN = Sweep Down
4 LEDs: GA1, GA2, GA3, and GA4
* LED: NSSW100CT (NICHIA)
80
70
60
ILED = 15.3 mA
50
ILED = 25.2 mA
40
2.9
3.9
0.14
0.12
0.10
ILED = 15.3 mA
0.08
ILED = 25.2 mA
0.06
0.04
ILED = 2.1 mA
0.02
ILED = 2.1 mA
3.4
VIN = Sweep Down
4 LEDs: GA1, GA2, GA3, and GA4
* LED: NSSW100CT (NICHIA)
0.16
IIN − Input Current − A
Efficiency − %
90
4.4
0.00
2.9
4.9
VIN − Input Voltage − V
3.4
3.9
4.4
4.9
VIN − Input Voltage − V
G001
G002
Figure 3.
Figure 4.
SHUT DOWN CURRENT
vs
INPUT VOLTAGE
OUTPUT CURRENT ACCURACY
vs
TEMPERATURE
2.0
10
1.5
Current Accuracy − %
Shutdown Current − µA
8
1.0
TA = 25°C
TA = −40°C
TA = 85°C
0.5
6
GA1
GA3
4
2
0
−2
−4
GA2
−6
GA4
−8
0.0
2.7
3.0
3.3
3.6
3.9
4.2
VIN − Input Voltage − V
4.5
−10
−40
4.8
G003
Figure 5.
6
−20
0
20
40
TA − Free-Air Temperature − °C
60
80
G004
Figure 6.
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
TPS60255
www.ti.com
SLVS825 – MARCH 2008
SWITCH RESISTANCE
vs
TEMPERATURE
1.5x mode, Io = 230 mA
2.0
5.0
1.8
4.5
1.6
4.0
1.4
Switch Resistance − Ω
Switch Resistance − Ω
SWITCH RESISTANCE
vs
TEMPERATURE
1x mode, Io = 230 mA
VCC = 3.3 V
1.2
VCC = 3.6 V
1.0
0.8
0.6
VCC = 3.9 V
0.4
VCC = 3.6 V
3.0
2.5
2.0
VCC = 3.9 V
1.5
1.0
0.2
0.0
−40
VCC = 3.3 V
3.5
0.5
−20
0
20
40
60
0.0
−40
80
TA − Free-Air Temperature − °C
−20
0
20
40
60
TA − Free-Air Temperature − °C
G005
Figure 7.
80
G006
Figure 8.
INPUT VOLTAGE
vs
OUTPUT VOLTAGE
TRANSITION
6
VOUT − Output Voltage − V
1.5× to 1× Mode Transistion Down
5
4
3
1× to 1.5× Mode Transistion Up
2
VIN = Sweep Down and Up
4 LEDs: GA1, GA2, GA3, and GA4
* LED: NSSW100CT (NICHIA)
1
0
2.9
3.4
3.9
4.4
VIN − Input Voltage − V
4.9
G007
Figure 9.
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
7
TPS60255
www.ti.com
SLVS825 – MARCH 2008
APPLICATION INFORMATION
APPLICATION OVERVIEW
Most of the current mobile telephone handsets fall into one of these designs:
• Clam Shell (Figure 17)—a main display on the inside, a secondary display on the outside, and a keypad
backlight.
• Slide type (Figure 18)—slide-up and slide-down design, with a main display and two keypads (inside and
outside).
• Bar (Figure 19)—a main display and a keypad backlight.
Charge pumps are becoming increasingly attractive for driving LEDs for the display backlight and keypad
backlight in handsets, where board space and maximum converter height are critical constraints. Its major
advantage is use of only capacitors as storage elements. TPS60255 is well suited for use in all three major
phone designs.
The device provides six 25 mA current regulators and one 80 mA current regulator. The current regulators are
divided into three groups (A, B, and C), with each group having its own independent current program register and
ON/OFF control. This promotes dividing and combining the groups for various LED driving configurations
including LCD backlight, keypad backlight, and camera flash light. See APPLICATIONS CIRCUITS for example
cell phone application circuits.
The TPS60255 adopts 1× and 1.5× charge pump configuration. The device monitors the voltage of the current
feedback pins (Gx pins) and automatically switches between 1× and 1.5× mode to ensure current regulation
regardless the variations of input voltage and LED forward voltage.
The TPS60255 uses only four external components, the input/output capacitors and two
charge-pump-flying-capacitors. This combined with the 16-pin, 3 mm × 3 mm QFN package (0.8 mm height),
provides for a small, low-profile total solution.
OPERATING PRINCIPLES
The TPS60255 charge-pump provides regulated LED current from a 2.7 V to 6.0 V input source. It operates in
two modes. The 1× mode, where the input is connected to the output through a pass element, and a high
efficiency 1.5× charge pump mode. The IC maximizes power efficiency by operating in 1× and 1.5× modes as
input voltage and LED current conditions require. The mode of operation is automatically selected by comparing
the forward voltage of the WLED plus the voltage of current sink for each LED with the input voltage.
The IC starts up in 1× mode, and automatically transitions to 1.5× mode if the voltage at any current sink input
(GAx, GBx, or GC) falls below the 100-mV transition voltage. The IC returns to 1× mode as the input voltage
rises. In 1.5× mode, the internal oscillator determines the charge/discharge cycles for the flying capacitors.
During a charge cycle, the flying capacitors are connected in series and charged up to the input voltage. After the
on-time of the internal oscillator expires, the flying capacitors are reconfigured to be in parallel and then
connected in series to the input voltage. This provides an output of 1.5× of the input voltage. After the off-time of
the internal oscillator expires, another charge cycle initiates and the process repeats.
8
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
TPS60255
www.ti.com
SLVS825 – MARCH 2008
VA
Vin
Vout
VF
TPS60255
VDX
1.5´ Mode
Operating Area
1´ Mode
Operating Area
Gear Up
Gear Down
Vin
Vhys
VB
VC
Figure 10. Input Voltage Hysteresis Between 1× and 1.5× Modes
As shown in Figure 10, there is input hysteresis voltage between 1× and 1.5× modes to ensure stable operation
during mode transition. For the single-cell Li-ion battery input voltage range, the TPS60255 operates in 1× mode
when a fully charged battery is installed. Once the battery voltage drops below the VB level, the WLED driver
operates in the 1.5× mode. Once in 1.5× mode with the same LED current condition, the battery voltage must
rise to the VC level in order to transition from 1.5× to 1× mode. This hysteresis ensures stable operation when
there is some input voltage fluctuation at the 1×/1.5× mode transition.
The input transition voltage (VB) depends on the drop out voltage of the charge pump stage (VA), WLED forward
voltage (VF), and the mode transition threshold voltage (VTH_GU). The input transition voltage is calculated as:
VB = VA + VF + VTH_GU
VA = RO_1X × IO
where RO_1X is the 1× mode output impedance and IO is the total output current.
See the ELECTRICAL CHARACTERISTICS table for output impedance specifications.
The TPS60255 switches to 1.5× mode when the input voltage is below VB and remains in the 1.5× mode as long
as the input is lower than VC. When the input voltage rises above VC, 1.5× Mode is exited. VC is calculated as:
VC = VF + 550mV
The input voltage mode transition hysteresis voltage (VHYS) between the 1× and 1.5× modes is calculated as:
VHYS = VC – VB = 550 mV – VTH_GU – VA, where VTH_GU = 100 mV
Note that VA is the key factor in determining VHYS and is dependant on the 1× mode charge pump output
impedance and WLED current.
Example: If we choose LWE67C (Osram) and set Iled = 15.3 mA, then VF = 3.55 V according to the LED
characteristics curve.
Total load current, IO = 15.3 mA × 6 = 91.8 mA
VB = RO1X * IO + VTH_GU + VF = 1*0.0918 + 0.1 + 3.55 = 3.748 (Gear up voltage)
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
9
TPS60255
www.ti.com
SLVS825 – MARCH 2008
VC = VF + 550 mV = 3.55 + 0.55 = 4.1 (Gear down voltage)
LED CURRENT SINKS (Group A, B, and C)
The TPS60255 has constant current sinks which drive seven individual LED current paths. Each current sink
regulates the LED current to a constant value determined by the single-wire EasyScale interface. The internal
register addressing controls the LED channels GA1 to GA4 independent of the GB1 to GB2 or the auxiliary
current path GC.
All the LED channels sink up to 25 mA of current, except GC which has an 80 mA maximum current. Using the
EasyScale interface, a user can assign GC to a torch, keypad light, or low/weak camera flash with 80 mA current
using four dimming steps (full scale, 70%, 40%, and 20%).
These optimized current sinks minimize the voltage headroom required to drive each LED and maximize power
efficiency by increasing the amount of time the controller stays in 1× mode before transitioning to the 1.5× mode.
10
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
TPS60255
www.ti.com
SLVS825 – MARCH 2008
OPEN LAMP DETECTION
In system production, it is often necessary to leave LED-current-paths open depending on the phone model. For
example, one phone can use two LEDs to backlight the main display, while another uses four LEDs. Rather than
use two different integrated circuits for these different phone applications, the TPS60255 can be used in both
applications. In traditional LED driver applications when an LED current path is open, the current sink voltage
falls to ground and the current regulation circuitry drives the output to a maximum voltage in an attempt to
regulate the current for the missing LED path. This can severely reduce the system efficiency. The TPS60255
uses seven internal comparators to detect when one or more open LED condition occurs and prevent activation
of 1.5X mode transition due to missing LEDs.
Input Voltage
1 V/div
Output voltage
1 V/div
Input current
RMS = 154.2 mV
Input current
100 mA/div
GA1 Current
100 mA/div
VIN = 4.0 V
GA1 = GA2 = GA3 = GA4 = 25.2 mA
GB1 = GB2 = 25.2 mA
Figure 11. Normal Operation (1× Mode)
Input Voltage
1 V/div
Output voltage
1 V/div
Input current
RMS = 129.2 mV
Input current
GA1 current
100 mA/div
100 mA/div
VIN = 4.0 V
GA4 is open
GA1 = GA2 = GA3 = 25.2 mA
GB1 = GB2 = 25.2 mA
Figure 12. Open Lamp Detection (1× Mode)
CAPACITOR SELECTION
The TPS60255 is optimized to work with ceramic capacitors having a dielectric of X5R or better. The two flying
capacitors must be the same value for proper operation. The 750-kHz switching frequency requires the flying
capacitor to be less than 4.7uF. Using 1uF ceramic capacitors for both charge-pump-flying-capacitors is
recommended. For good input voltage filtering, low ESR ceramic capacitors are recommended. A 1uF ceramic
input capacitor is sufficient for most of the applications. For better input voltage filtering this value can be
increased to 4.7uF. The output capacitor determines the amount of ripple on the output. A 4.7uF output capacitor
is recommended for the output capacitor. If better output filtering and lower ripple are desired, a larger output
capacitor may be used.
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
11
TPS60255
www.ti.com
SLVS825 – MARCH 2008
EasyScale: Single-pin serial interface for ON/OFF and brightness control
General
EasyScale is a simple, but very flexible single-pin interface. The interface is based on a master/slave structure,
where the master is typically a microcontroller or application processor. The advantage of EasyScale compared
to other single-pin interfaces is that its bit detection is largely independent of the bit transmission rate. It can
automatically detect bit rates from 1.2 Kbps up to 95 Kbps.
Protocol
All bits are transmitted MSB first and LSB last. Figure 14 (Timing & Bit coding) shows the protocol without
acknowledge (Bit RFA = 0) and Figure 15 shows the protocol with acknowledge (Bit RFA = 1) request.
Prior to both bytes (Table 1—device address byte and Table 2—data byte), a start condition must be applied. For
this, the IF pin must be pulled high for at least tstart (3.5µs) before the bit transmission starts with the falling edge.
If the IF pin is already at high level, no start condition is needed prior to the device address byte.
The transmission of each byte is closed with an End of Stream condition for at least tEOS (3.5us).
DATA IN
Device Address
Start
Start
DATABYTE
DA3 DA2 DA1
0
0
1
DA7 DA6 DA5 DA4
0
0
0
1
DA0 EOS Start RFA
0
A0
A1
D4
D3
D2
D1
D0
EOS
DATA OUT
ACK
Figure 13. EasyScale Protocol Overview
Table 1. EasyScale Bit Description for Address Byte
BIT
NUMBER
NAME
TRANSMISSION
DIRECTION
DESCRIPTION
7 (MSB)
DA7
IN
6
DA6
DA6
5
DA5
DA5
4
DA4
DA4
3
DA3
DA3
2
DA2
DA2
1
DA1
DA1
0 (LSB)
DA0
DA0 LSB device address
DA7 MSB Device Address
Table 2. EasyScale Bit Description for Data Byte
BIT
NUMBER
NAME
7(MSB)
RFA
6
A1
Address Bit 1
5
A0
Address Bit 0
4
D4
3
D3
2
D2
Data Bit 2
1
D1
Data Bit 1
0 (LSB)
D0
Data Bit 0
ACK
12
TRANSMISSION
DIRECTION
DESCRIPTION
Request For Acknowledge, if high, Acknowledge condition applied by the device
IN
OUT
Data Bit 4
Data Bit 3
Acknowledge condition active 0, this condition is only applied when the RFA bit is set. Open
drain output, that is, line needs to be pulled high by the host with a pullup resistor.
This feature can only be used if the master has an open drain output stage. In case of a push
pull output stage, Acknowledge condition can not be requested.
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
TPS60255
www.ti.com
SLVS825 – MARCH 2008
Bit Detection
The bit detection is based on a Logic Detection scheme, where the criterion is the relation between tLOW and
tHIGH.
It can be simplified to:
• High Bit: tHigh > tLow, but with tHigh at least twice the duration of tLow, see Figure 16.
• Low Bit : tHigh < tLow, but with tLow at least twice the duration of tHigh, see Figure 16.
The bit detection starts with a falling edge on the IF pin and ends with the next falling edge. Depending on the
relation between tHigh and tLow, the logic 0 or 1 is detected.
Acknowledge
The acknowledge condition is applied only if:
• Acknowledge is requested by a set RFA bit.
• The transmitted device address matches with the device's address.
• All 16 bits are received correctly.
If the device turns on the internal ACKN-MOSFET and pulls the IF pin low for the time tACKN, which is 512 µs
maximum, then the Acknowledge condition is valid after an internal delay time tvalACK. This means that the
internal ACKN-MOSFET is turned on after tvalACK, when the last falling edge of the protocol was detected. The
master controller keeps the line low in this period. The master device can detect the acknowledge condition with
its input by releasing the IF pin after tvalACK and read back a logic 0. The IF pin can be used again after the
acknowledge condition ends.
Note that the acknowledge condition can only be requested in case the master device has an open drain output.
For a push-pull output stage, using a series resistor in the IF line to limit the current to 500 µA is recommended
to:
• Prevent an accidental request of acknowledge.
• Protect the internal ACKN-MOSFET.
MODE Selection
tStart
DATA IN
tStart
Address Byte
DATA Byte
Mode, Static
High or Low
Mode, Static
High or Low
DA7
0
DA0
0
TEOS
RFA
0
D0
1
TEOS
Figure 14. EasyScale Protocol Without Acknowledge (RFA=0)
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
13
TPS60255
www.ti.com
SLVS825 – MARCH 2008
tStart
DATA IN
tStart
Address Byte
DATA Byte
Mode, Static
High or Low
Mode, Static
High or Low
DA7
0
DA0
0
D0
1
RFA
1
T EOS
tvalACK
Controller needs to
Pullup Data Line via a
resistor to detect ACKN
DATA OUT
ACKN
tACKN
Acknowledge
true, Data Line
pulled down by
device
Acknowledge
false, no pull
down
Figure 15. EasyScale Protocol With Acknowledge (RFA=1)
tLow
tHigh
Low Bit
(Logic 0)
tLOW
tHigh
High Bit
(Logic 1)
Figure 16. EasyScale Bit Coding
Control Registers of TPS60255 Using EasyScale
Group B Display Current Control Register
Group B
DISP
CURRENT
BIT data
A1
A0
D4
D3
D2
D1
D0
0
0
IB4
IB3
IB2
IB1
IB0
Bit 4 to Bit 0
(IB4 to IB0)
5-bit command (32 steps) to set the current for Group B
For LED currents between 100 µA and 1.0 mA, one step = 100 µA.
For LED currents between 1.0 mA and 25.2 mA, one step = 1.1 mA.
Group A Display Current Control Register
Group A
DISP
CURRENT
BIT data
14
A1
A0
D4
D3
D2
D1
D0
0
1
IA4
IA3
IA2
IA1
IA0
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
TPS60255
www.ti.com
Bit 4 to Bit 0
(IA4 to IA0)
SLVS825 – MARCH 2008
5-bit command (32 steps) to set the current for Group A
For LED currents between 100 µA and 1.0 mA, one step = 100 µA.
For LED currents between 1.0 mA and 25.2 mA, one step = 1.1 mA.
Current Control Register Values
Table 3. Current Control Register Value for Group A and B
Number
Current (mA)
D4
IA4 (IB4)
D3
IA3 (IB3)
D2
IA2 (IB2)
D1
IA1 (IB1)
D0
IA0 (IB0)
0
0.1
0
0
0
0
0
1
0.2
0
0
0
0
1
2
0.3
0
0
0
1
0
3
0.4
0
0
0
1
1
4
0.5
0
0
1
0
0
5
0.6
0
0
1
0
1
6
0.7
0
0
1
1
0
7
0.8
0
0
1
1
1
8
0.9
0
1
0
0
0
9
1.0
0
1
0
0
1
10
2.1
0
1
0
1
0
11
3.2
0
1
0
1
1
12
4.3
0
1
1
0
0
13
5.4
0
1
1
0
1
14
6.5
0
1
1
1
0
15
7.6
0
1
1
1
1
16
8.7
1
0
0
0
0
17
9.8
1
0
0
0
1
18
10.9
1
0
0
1
0
19
12.0
1
0
0
1
1
20
13.1
1
0
1
0
0
21
14.2
1
0
1
0
1
22
15.3
1
0
1
1
0
23
16.4
1
0
1
1
1
24
17.5
1
1
0
0
0
25
18.6
1
1
0
0
1
26
19.7
1
1
0
1
0
27
20.8
1
1
0
1
1
28
21.9
1
1
1
0
0
29
23.0
1
1
1
0
1
30
24.1
1
1
1
1
0
31
25.2
1
1
1
1
1
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
15
TPS60255
www.ti.com
SLVS825 – MARCH 2008
Enable Control Register
ENABLE
A1
A0
D4
D3
D2
D1
D0
BIT data
1
0
EN_OLD
EN_GB1
EN_GB2
EN_GA
EN_GA4
Bit 4 (EN_OLD)
1: Open Lamp Detection Enabled
0: Open Lamp Detection Disabled
Bit 3 (EN_GB1)
1: Enable GB1
0: Disable GB1
Bit 2 (EN_GB2)
1: Enable GB2
0: Disable GB2
Bit 1 (EN_GA)
1: Enable GA1 to GA3
0: Disable GA1 to GA3
Bit 0 (EN_GA4)
1: Enable GA4
0: Disable GA4
GC Brightness and Operation Mode Control Register
Aux
DISP
CURRENT
BIT data
A1
A0
D4
D3
D2
D1
D0
1
1
Mode1
Mode0
GC0
GC1
EN_GC
Bit 4 to Bit 3
Mode1
Mode0
TPS6055 Mode
0
0
Auto-switchover Mode. The TPS60255 selects 1× or 1.5× mode
automatically as described in the OPERATING PRINCIPLES section.
1
1
Shut down, All LED current shuts down.
1
0
1× Mode. TPS60255 remains in 1× mode regardless of the input voltage.
LED current can not regulate at lower input voltages when in this mode.
0
1
1.5× Mode. TPS60255 remains in 1.5× mode regardless of the input
voltage
Bit 2 to Bit 1
2-bit command (four steps) to set the current for GC
16
GC0
GC1
Dimming Step
0
0
20 %
1
0
40 %
0
1
70 %
1
1
100 %
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
TPS60255
www.ti.com
SLVS825 – MARCH 2008
Bit 0
EN_GC
1: Enable GC
0: Disable GC
ADDITIONAL APPLICATION CIRCUITS
These application circuits apply to the common designs for mobile telephones:
• Clam Shell (Figure 17)—application circuit for driving four LEDs for main display and two LEDs for the
subdisplay.
• Slide (Figure 18)—application circuit for driving four LEDs for LCD display backlight and LEDs for both suband main keypad backlight.
• Bar (Figure 19)—application circuit for driving four LEDs for LCD display backlight and LEDs for key pad
backlight.
AUX
(key pad)
Main Display
GND
C1-
C2
1 mF
C3
1 mF
GC
GA4
GA3
GA2
C2+
GA1
C2-
GB2
C1+
GB1
VIN
ENA
IF
Sub Display
VOUT
C4
2.2 mF
C1
4.7 mF
Enable/
Disable
Interface Using
EasyScale
Figure 17. Application Circuit—Clam Shell Mobile Phone Design
AUX
(Main key pad)
Main Display
GND
C1-
C2
1 mF
C3
1 mF
GC
GA4
GA3
GA2
C2+
GA1
C2-
GB2
C1+
GB1
VIN
ENA
Sub keypad
VOUT
C4
2.2 mF
IF
C1
4.7 mF
Enable/
Disable
Interface Using
EasyScale
Figure 18. Application Circuit—Slide Mobile Phone Design
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
17
TPS60255
www.ti.com
SLVS825 – MARCH 2008
AUX
(key pad)
Main Display
GND
C1-
C2
1 mF
C3
1 mF
GC
GA4
GA3
GA2
C2+
GA1
C2-
GB2
C1+
GB1
VIN
ENA
IF
VOUT
C4
2.2 mF
C1
4.7 mF
Enable/
Disable
Interface Using
EasyScale
Figure 19. Application Circuit—Bar Mobile Phone Design
18
Submit Documentation Feedback
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS60255
PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
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)
(4/5)
(6)
TPS60255RTER
ACTIVE
WQFN
RTE
16
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
BUP
TPS60255RTET
ACTIVE
WQFN
RTE
16
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
BUP
(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
工商网监
湘ICP备2023018690号
