TPS60230RGTT [TI]
采用 3x3 QFN 封装、用于白光 LED 背光的 5 通道、电流调节型 125mA 电荷泵 | RGT | 16 | -40 to 85;
| 型号： | TPS60230RGTT |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 采用 3x3 QFN 封装、用于白光 LED 背光的 5 通道、电流调节型 125mA 电荷泵 | RGT | 16 | -40 to 85 泵 |
| 文件： | 总15页 (文件大小：374K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
WHITE LED CHARGE PUMP CURRENT SOURCE
WITH PWM BRIGHTNESS CONTROL
FEATURES
DESCRIPTION
•
Regulated Output Current With 0.3%
Matching Over Temperature
The TPS60230 charge pump is optimized for white
LED supplies in backlit color display applications. The
device provides a constant current, set by an external
resistor, for each LED. The supply voltage ranges
from 2.7 V to 6.5 V and is ideally suited for all
applications powered by a single LI-Ion battery cell or
three to four NiCd, NiMH, or Alkaline battery cells.
The TPS60230 provides up to 25 mA per LED, for a
total of 125 mA, for input voltages ranging from 3.1 V
to 6.5 V. High efficiency is achieved by utilizing a
1x/1.5x fractional conversion technique in combi-
nation with very low dropout current sources. Ad-
ditionally, the current controlled charge pump ensures
low input current ripple and EMI. Only two external 1
µF and two 0.47 µF capacitors are required to build a
complete small and low cost power supply solution.
The TP60230 switches at 1 MHz operating frequency
and is available in a small 16-pin QFN (RGT)
package to keep board space to a minimum.
•
•
Drives up to 5 LEDs at 25 mA Each
LED Brightness Control Through PWM
Control Signal
•
High Efficiency by Fractional Conversion
With 1x and 1.5x Modes
•
•
•
•
•
•
•
1 MHz Switching Frequency
2.7 V to 6.5 V Operating Input Voltage Range
Internal Softstart Limits Inrush Current
Low Input Ripple and Low EMI
Overcurrent and Overtemperature Protected
Undervoltage Lockout With Hysteresis
Ultra-Small 3mm x 3mm QFN Package
APPLICATIONS
•
White LED Backlight for Color Displays in
Cellular Phones, Smart Phones, PDAs,
Handheld PCs, Digital Cameras,
and Camcorders
VIN
VOUT
1 mF
VIN = 2.7 V
to 6.5 V
C1+
D1
D2
0.47 mF
0.47 mF
C1−
C2+
C2−
•
Key Backlight
D3
D4
D5
1 mF
EN1
EN2
GND
ISET
PGND
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.
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 © 2004, Texas Instruments Incorporated
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
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.
ORDERING INFORMATION
PACKAGED DEVICE(1)(2)
PACKAGE
MARKING
TPS60230RGTR
QFN
BIZ
(1) T indicates shipment in tape and reel on a mini reel with 250 units
per reel.
(2) R indicates shipment in tape and reel with 3000 units per reel.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted)(1)
UNIT
–0.3 V to 7 V
–0.3 V to VI
200 mA
VI
Supply voltage
Voltage at EN1, EN2, VOUT, ISET
Output current at VOUT
TJ
Maximum junction temperature
Operating free-air temperature
Storage temperature
150°C
TA
Tst
–40°C to 85°C
–65°C to 150°C
300°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds
(1) 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.
DISSIPATION RATINGS(1)
TA≤ 25°C
POWER RATING
DERATING FACTOR
ABOVE TA = 25°C
TA = 70°C
POWER RATING
TA = 85°C
POWER RATING
PACKAGE
16-Pin QFN (RGT)
1.9 W
20 mW/°C
1 W
760 mW
(1) The thermal resistance junction to ambient of the QFN package is 52 °C/W.
RECOMMENDED OPERATING CONDITIONS
MIN TYP
MAX UNIT
Supply voltage at VIN
2.7
125
1
6.5
V
Maximum output current at VOUT
mA
µF
µF
µF
°C
Ci
Co Output capacitor
Flying capacitor, C1, C2
Operating junction temperature
Input capacitor
0.47
1
0.22 0.47
-40
125
2
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
ELECTRICAL CHARACTERISTICS
VI = 3.6 V, EN1 = EN2 = VI, TA = -40°C to 85°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN TYP MAX UNIT
SUPPLY VOLTAGE AND CURRENT
VI
Input voltage range
IO = 0 mA to 75 mA
2.7
6.5
1
V
VI = 4.2 V, x1-mode, EN1 = EN2 = 1, ISET = 20 µA
IO = 0 mA, x1.5-mode
200
2.1
0.1
µA
mA
µA
IQ
Operating quiescent current
Shutdown current
ISD
EN2 = EN1 = GND
CHARGE PUMP STAGE
VOUT
Overvoltage limit
LED1 unconnected, VI = 4.2 V
5.5
375
160
1
V
µs
Startup time
CO = 1 µF, IDX≥ 0.9 IDX, set
Softstart duration
Switching frequency
Efficiency
µs
f
0.75
1.25
MHz
η
VI = 3.7 V, ILED = 15 mA each, VDX = 3.1 V
Temperature rising
83%
160
20
Shutdown temperature
Shutdown temperature hysteresis
Input current limit
°C
°C
EN2 = EN1 = 1, ISET = 100 µA
3.2 V ≤ VI≤ 6.5 V
350
mA
CURRENT SINKS
Recommended maximum current per cur-
rent sink
25
50
mA
mA
IDx
IDx
Current into each current sink when Iset is
shorted to GND
3.0 V ≤ VI≤ 6.5 V, ISET shorted to GND
Current matching between any two outputs VDx = 3.1 V, TA = 25°C
–2% 0.4%
2%
3.2 V ≤ VI≤ 6.5 V, VDx = 3.1 V, EN1 = EN2 = 1,
ISET = 80 µA
±3%
Line regulation
EN2 = 0, EN1 = 1
EN2 = 1, EN1 = 0
EN2 = 1, EN1 = 1
200
400
VISET
Reference voltage for current set
mV
µA
580 600 620
130
Iset
k
Recommended ISET pin current range
IDx to Iset current ratio
4
EN2 = EN1 = 1, ISET = 80 µA
EN2 = 0, EN1 = 1
230 260 280
200
300
400
Vsource Voltage at Dx to GND
EN2 = 1, EN1 = 0
mV
EN2 = 1, EN1 = 1
ENABLE 1, ENABLE 2
VIH
VIL
EN1, EN2 high level input voltage
1.3
0.3
50
V
V
EN1, EN2 low level input voltage
EN1, EN2 trip point hysteresis
EN2 input leakage current
EN1 input current
mV
µA
µA
V
IIKG
II
EN1, EN2 = GND or EN2 = VI, VI = 6.5 V
EN1 = VI, VI = 4.2 V
0.01
11
1
15
V(UVLO) Undervoltage lockout threshold
Undervoltage lockout hysteresis
Frequency range at PWM
Input voltage falling
2.1
50
mV
kHz
µs
0
50
Recommended ON-time for PWM signal
2.5
Delay time when EN1 = EN2 go to GND after which
the TPS60230 shuts down completely
Shutdown delay time
0.5 0.85
1.5
ms
3
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
PIN ASSIGNMENT
QFN PACKAGE
(TOP VIEW)
12
11
10
9
13
14
15
16
VOUT
PGND
D1
VIN
8
GND
7
6
5
EN1
EN2
D2
1
2
3
4
Terminal Functions
TERMINAL
I/O
DESCRIPTION
NAME
C1+
NO.
10
11
9
–
–
–
–
I
Connect to the flying capacitor C1
Connect to the flying capacitor C1
Connect to the flying capacitor C2
Connect to the flying capacitor C2
C1–
C2+
C2–
12
6-2
D1-D5
Current sink input. Connect the cathode of the white LEDs to these inputs.
Enable input. A logic high enables the converter, logic low forces the device into shutdown mode reducing the
supply current to less than 1 µA if EN2 is tied to GND.
EN1
EN2
15
I
An applied PWM signal reduces the LED current as a function of the duty cycle of the PWM signal. EN1 and EN2
can be tied together for PWM dimming between 0 mA and the maximum set with ISET. EN1 and EN2 can also be
used for digital dimming with 4 steps from 0 mA to the maximum current set with ISET. See the application section
for more details.
16
I
GND
ISET
PGND
VIN
14
1
–
I
Analog ground
Connect a resistor between this pin and GND to set the maximum current through the LEDs.
Power ground, connect with analog ground (GND)
Supply voltage input
7
–
I
13
8
VOUT
0
Connect the output capacitor and the anode of the LEDs to this pin.
Power
PAD
–
–
Connect with PGND and GND
4
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
FUNCTIONAL BLOCK DIAGRAM
1 mF
VOUT
C1+
D5
0.47 mF
0.47 mF
D4
D3
Current
Sinks
C1−
C2+
Charge
Pump
D2
D1
C2−
VIN
1 mF
Reference
Control
ISET
EN1
EN2
R
SET
PGND
GND
5
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
vs Input voltage (ILED = 25 mA, 15 mA, 10 mA per LED), EN2 = 0,
EN1 = 1, Show hysteresis (rising and falling VI), VLED = 3.1 V
1
2
vs Input voltage (ILED = 25 mA, 15 mA, 10 mA per LED), EN2 = 1,
EN1 = 0, Show hysteresis (rising and falling VI), VLED = 3.1 V
η
Efficiency
vs Input voltage (ILED = 25 mA, 15 mA, 10 mA per LED),
3
EN2 = EN1 = 1, Show hysteresis (rising and falling VI), VLED = 3.1 V
IQ No load quiescent current
vs Input voltage (TA = –40°C, 25°C, 85°C) (measured with ID1 = 5 mA)
4
5
6
7
Maximum output current from charge pump stage vs Input voltage
fs Switching frequency
vs Free-Air Temperature (TA = -40°C to 85°C, VI = 3.6 V)
vs Duty cycle on PWM (ILED max set to 20 mA)
For f = 32 kHz and f = 1 kHz, DC = 1% to 100%, VI = 3.6 V
LED current, ILED
VI and ID1 vs time on scope, Show LED current at D1 with
VI = 4.2 V to 3.6 V to 4.2 V with EN2 = EN1 = 11, 5x20 mA
8
9
Line transient response
Show PWM signal and current at D1 vs time on scope
f = 32 kHz, VI = 3.6 V, duty cycle = 50%, EN1 = EN2 = PWM
Dimming response
Startup timing
Show PWM signal and current at D1 vs time on scope
f = 1 kHz, VI = 3.6 V, duty cycle = 50%, EN1 = EN2 = PWM
10
11
VI = 3.6 V, 5x20 mA, EN1 = EN2 = 00 changed to EN2 = EN1 = 11
EFFICIENCY
vs
INPUT VOLTAGE
EFFICIENCY
vs
INPUT VOLTAGE
100
90
I
= 25 mA
LED
I
= 25 mA
90
80
70
60
50
40
30
20
10
0
LED
80
70
60
50
40
30
I
= 15 mA
LED
I
= 15 mA
LED
I
= 10 mA
LED
I
= 10 mA
LED
20
10
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9 6.3 6.5
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9 6.3 6.5
V − Input Voltage − V
I
V − Input Voltage − V
I
Figure 1.
Figure 2.
6
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
EFFICIENCY
vs
INPUT VOLTAGE
QUIESCENT CURRENT
vs
INPUT VOLTAGE
3
90
80
70
60
50
40
30
20
I
= 25 mA
LED
2.8
2.6
2.4
2.2
2
I
= 15 mA
LED
T
A
= 255C
1.8
1.6
1.4
1.2
1
T
= −405C
A
I
= 10 mA
LED
T
A
= 855C
0.8
0.6
0.4
0.2
0
10
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9 6.3 6.5
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9 6.3 6.5
V − Input Voltage − V
I
V − Input Voltage − V
I
Figure 3.
Figure 4.
MAXIMUM OUTPUT CURRENT
SWITCHING FREQUENCY
vs
FREE-AIR TEMPERATURE
vs
INPUT VOLTAGE
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
1040
1030
1020
1010
1000
990
T
= 255C
A
V = 3.6 V
I
V
= 3.2 V
LED
V
= 3.4 V
LED
V
LED
= 3 V
V
LED
= 3.6 V
V
= 3.8 V
LED
980
−40
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9 6.3 6.5
−30 −20 −10
0
10 20 30 40 50 60 70 80
V − Input Voltage − V
I
T
A
− Free-Air Temperature − 5C
Figure 5.
Figure 6.
7
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
D1 LED CURRENT
vs
DUTY CYCLE
LINE TRANSIENT
25
20
15
10
5
EN1 = 1, EN2 = 1, V = 3.6 V to 4.2 V,
I
V = 3.6 V,
I
= 20 mA, 5 LEDs Connected,
I
LED
I
Measured With 1 W Resistor,
I
max = 20 mA
LED(D1)
= 255C
LED
T
A
V
I
f = 1 kHz
3.6 V
f = 32 kHz
I
LED(D1)
AC
0
0
10 20 30 40 50 60 70 80 90 100
Duty Cycle − %
100 ms/div
Figure 8.
DIMMING RESPONSE
Figure 7.
DIMMING RESPONSE
PWM
PWM
0 V
0 V
PWM Into EN1 and EN2, V = 3.6 V,
LED
I
PWM Into EN1 and EN2, V = 3.6 V,
LED
I
I
= 20 mA, 5 LEDs Connected,
I
= 20 mA, 5 LEDs Connected,
f = 32 kHz, T = 255C
A
f = 1 kHz, T = 255C
A
I
LED(D1)
I
LED(D1)
0 A
0 A
200 ms/div
Figure 10.
5 ms/div
Figure 9.
8
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
STARTUP TIMING
EN1 + EN2
0 V
VOUT
V = 3.6 V, I
= 20 mA,
I
LED
5 LEDs Connected,
T
A
= 255C
0 V
0 A
I
I
20 µs/div
Figure 11.
DETAILED DESCRIPTION
OPERATION
The TPS60230 uses a fractional conversion charge pump to generate a supply voltage for the integrated current
sinks. These current sinks are used to ensure a constant current for each LED. Depending on the input voltage
and programmed LED current, the charge pump either operates in the 1x mode or in the 1.5x mode. By
switching automatically between these two modes, the circuit optimizes power conversion efficiency as well as
extends operating time by allowing the discharge of the battery completely.
The charge pump can generate 125 mA of output current, so each of the 5 LED outputs can be powered with up
to 25 mA of current. The maximum LED current is set by a resistor connected to the ISET pin. This resistor
programs a reference current, which is current mirrored to set the LED current.
Applying a PWM signal to the EN1 pin and/or the EN2 pin controls the LED brightness. See a detailed
description in the section Analog Dimming Using ISET Pin.
LED CURRENT ADJUSTMENT (ISET)
A resistor programs a reference current, which is current mirrored to set the LED current. The voltage at the
ISET pin depends on the status of EN1 and EN2. The current in each LED is typically 260 times the current
through the resistor at ISET.
V
ISET
R
+
k
ISET
I
LED
VISET— Voltage from ISET pin (0.2 V, 0.4 V or 0.6 V) to GND, see Table 1
ILED— Current per LED from Dx pin to GND
k — ISET to Dx current ratio
The LED current varies linearly from 0 mA to ILED(max) mA by applying a PMW signal with 0% to 100% duty cycle.
The LED brightness can however also be controlled by an analog control signal that is fed into the ISET pin.
9
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
DETAILED DESCRIPTION (continued)
SOFT START
The TPS60230 has an internal soft start circuit to limit the inrush current during startup. This prevents possible
voltage drops of the input voltage if a high impedance power source is connected to the input of the TPS60230.
When the device starts up with an output voltage that is below the input voltage, the output capacitor is charged
directly from the input with a current source. The output current increases linearly until the output reaches within
300 mV of the input voltage. When the programmed output current can be reached with the 1x mode, the
TPS60230 terminates the soft start and begins normal operation. When the desired output current cannot be
reached, the charge pump begins operation in 1.5x mode and pumps the output voltage up to the needed level
to reach the programmed output current.
ENABLE (EN1, EN2)
The enable pins EN1 and EN2 are used to enable the device or set it into shutdown. The TPS60230 is enabled if
one of the enable pins is pulled higher than the enable trip point of 1.3 V. The device starts up by going through
the soft start routine as described in the section Soft Start. Pulling both pins to GND, after a delay, programs the
device to shutdown. In shutdown, the charge pump, current sources, voltage reference, oscillator, and all other
functions are turned off and the supply current is reduced to 0.1 µA.
EN1 and EN2 can also be used for dimming. The logic levels at EN1 and EN2 set the minimum voltage at the
current mirrors and the voltage at the ISET pin to GND. This sets the current at the LEDs to be either the full
current or a fraction of the full current. See Table 1 for further details. The maximum current through the LEDs is
set by a resistor connected between ISET and GND.
EN1 and EN2 can also be used for PWM dimming. The PWM signal can either be applied to EN1 or EN2, or
both inputs can be tied together and the PWM signal can be applied to both pins. Depending on the
configuration, the current during PWM dimming is switched between 0 mA and its maximum (EN1 and EN2
connected to the PWM signal) or between 0 mA and 1/3 of the full LED current if EN2 = 0 and EN1 is toggled.
When EN1 = 0 and EN2 is toggled, the output current can be changed between 0 mA and 2/3 of the full range.
Table 1. Enable Levels
ENABLE LEVEL
MODE
LED CURRENT
EN2
EN1
0
0
1
1
0
1
0
1
SHUTDOWN
VISET = 200 mV
VISET = 400 mV
VISET = 600 mV
0
1/3
2/3
Full
UNDERVOLTAGE LOCKOUT
The undervoltage lockout circuit shuts down the device when the voltage at VIN drops below a typical threshold
of 2.15 V. This prevents damage to the device. The UVLO circuit allows the device to start up again after the
voltage on the VIN pin has increased by about 100 mV above the UVLO lockout threshold.
SHORT CIRCUIT AND OVERTEMPERTURE PROTECTION
The current at the VOUT pin is limited typically to 250 mA. When the junction temperature exceeds 155°C, the
device shuts down to protect the device from damage. After the temperature decreases to about 135°C, the
device starts up again if it is enabled.
OVERVOLTAGE PROTECTION AT VOUT
The device uses the voltage at D1 to regulate voltage at VOUT. In case D1 is not connected, an overvoltage
protection circuit ensures that the output voltage at VOUT does not exceed its limits. The connection of the LEDs
must be started using D1 first. For all other LEDs there is no restriction in the sequence. For example, if there
are only 3 LEDs used, the first LED is connected to D1 and the other two LEDs can be connected to any other of
the D2 to D5 pins.
10
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
THEORY OF OPERATION/DESIGN PROCEDURE
Capacitor Selection
Ceramic capacitors such as X5R or X7R are recommended to be used with the TPS60230. For the two flying
capacitors C1 and C2, it is important to use low ESR capacitors to avoid unnecessary efficiency losses. Low
ESR capacitors on VOUT reduce the ripple voltage on the supply of the current sources. Table 2 lists capacitor
types that have been tested with the TPS60230.
Table 2. Capacitors
PART
VALUE
VOLTAGE
MANUFACTURER
SIZE
WEBSITE
C1608X5R1A105M
C1608X5R1A474M
C2012X7R1C105M
1 µF
0.47 µF
1µ F
10 V
10 V
16 V
0603
0603
0805
TDK
www.componnent.tdk.com
LMK107BJ105MA
LMK107BJ474MA
LMK212BJ105MG
1 µF
0.47 µF
1µ F
10 V
10 V
10 V
0603
0603
0805
Taiyo Yuden
www.t-yuden.com
Power Efficiency
The power conversion efficiency of the TPS60230 can be calculated by adding up the products of each LED
current and voltage and dividing it by the product of the input voltage and current. With a fully charged battery
where the input voltage is typically above the LED forward voltage, the charge pump operates in the 1x mode
and efficiency is very high. As the battery discharges, there is a point where the current sources no longer have
enough voltage overhead to maintain a constant current regulation. At that point, the charge pump switches into
the 1.5x mode. The conversion efficiency is lowest at the crossover. As the battery discharges further, the
efficiency again increases until at about 3.1 V where it reaches a second maximum. Below 3.1 V input voltage,
the maximum current per LED is less than 25 mA.
Power Dissipation
The maximum power dissipation inside the TPS60230 can be calculated based on the following equation:
PD max = [(1.5 × VI) – VO + 0.4 V] × IO
The maximum power dissipation occurs when the input voltage is just low enough to operate in 1.5x mode, with
a forward voltage of the white LED at maximum. This is typically for VI = 4.2 V and a forward voltage of 3.6 V.
This needs to be lower than the maximum allowed power dissipation of the package, which can be calculated
using the following equation:
T
T
Jmax
T
A
P
+
D max, package
qja
For example, the worst case power dissipation occurs at the input voltage level where the charge pump switches
from the 1x mode to the 1.5x mode. At this operating point, the supply voltage to the current sources is at its
maximum and the current sources must drop the most voltage in order to maintain a regulated output current.
The worst case power dissipation occurs when all 5 LED outputs are fully loaded with 25 mA of LED current.
•
•
With: VI = 4.2 V, Vf = 3.6 V, IO = 125 mA (1.5x mode)
PD max = 0.39 W
11
TPS60230
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SLVS516A–MAY 2004–REVISED JUNE 2004
APPLICATION INFORMATION
TYPICAL APPLICATION OF A SMART PHONE DISPLAY WITH RESISTORS CONNECTED IN
PARALLEL
If more than 25 mA of output current is needed, then the input pins to the current sinks can be connected in
parallel as shown in the following application figure. This method can also be used to connect a LC display with
only two connections for the white LEDs.
VIN
VOUT
VIN = 2.7 V
to 6.5 V
C1+
1 mF
D1
D2
0.47 mF
0.47 mF
C1−
C2+
C2−
D3
D4
D5
1 mF
EN1
EN2
GND
ISET
PGND
Typical Smartphone Display
Figure 12. Typical Application With Resistors in Parallel
ANALOG DIMMING USING ISET PIN
The ISET pin can be used to connect an analog dc signal in the range of 0 mV to 600 mV (EN1 = EN2 = 1) for
analog dimming of the white LEDs. For an input voltage of 0 V at ISET, the current is at its maximum, whereas at
600 mV, the LED current is zero. The maximum current is:
•
•
•
•
For EN2 = EN1 = 1: ILED = Vset/Rset × K = 0.6V/6kR × 270 = 27 mA per LED
For EN2 = 1, EN0 = 1: ILED = Vset/Rset × K = 0.4V/6kR × 270 = 18 mA per LED
For EN2 = 0, EN1 = 1: ILED = Vset/Rset × K = 0.2V/6kR × 270 = 9 mA per LED
With EN2, EN1 set to 10 or 01, a voltage of 400 mV or 200 mV is required to set the LED current to zero.
VIN
VOUT
1 mF
VIN = 2.7 V
to 6.5 V
C1+
D1
D2
0.47 mF
0.47 mF
C1−
C2+
C2−
D3
D4
D5
1 mF
EN1
EN2
GND
ISET
6 kW
V = 0 mV to
600 mV
PGND
Figure 13. Analog Dimming Connections Using ISET Pin
12
TPS60230
www.ti.com
SLVS516A–MAY 2004–REVISED JUNE 2004
APPLICATION INFORMATION (continued)
TYPICAL APPLICATION USING 2 WHITE LEDs AND 6 GREEN LEDs FOR LCD BACKLIGHT AND
KEYBOARD LIGHTING
The TPS60230 can be used to power any kind of LED. It is also possible to mix white LEDs with color LEDs
which have a lower forward voltage. The LED with the highest forward voltage (typically the white LED) has to be
connected to D1, because the output voltage of the charge pump is regulated in such a way to keep the voltage
drop from D1 to GND at 400mV (with EN1 = EN2 = 1). Therefore the output voltage of the charge pump is
regulated to:
V
= V + V
D1 FLEDD1
OUT
VOUT— Output voltage at VOUT
VD1— Voltage from D1 to GND (Vsource at D1 pin, see electrical characteristics)
VFLEDD1— Forward voltage of the LED connected to D1
Resistor Rg is used to provide current sharing between the 6 green LEDs. The upper value is calculated using:
V
V
FLEDD1
Fg
R
+
g
I
g
VFg— Forward voltage of a green LED
Ig— Current per green LED
VIN
VOUT
1 mF
VIN = 2.9 V
C1+
D1
D2
to 6.5 V
0.47 mF
2 White
LEDs With
C1−
30 mA Each
D3
D4
D5
C2+
C2−
0.47 mF
6 Green
LEDs With
5 mA Each
1 mF
EN1
EN2
ISET
GND
Sets Current to 30 mA
Per Current Sink
(With EN2 = EN1 = 1)
PGND
5.4 kW
Figure 14. LED Connections for LCD Backlight and Keyboard Lighting
PROPOSED LAND PATTERN FOR PCB PRODUCTION
Refer to the application note SLUA271 for the proposed land pattern of the QFN package.
PHOTO FLASH APPLICATIONS
The TPS60230 can be used to power one or more white LEDs for photo flash applications. These applications
usually require a certain current for a short period of time. The photo flash is typically turned on for 100 ms to
500 ms and turned off for a longer period of time. For such applications, when the TPS60230 is not turned on
continuously, the device can support an output current of 150 mA. See Figure 5 for the input voltage needed for
a certain LED forward voltage and LED current.
13
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