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STLA02
User Manual
23 pgs724.57 Kb0
Table of contents
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ST STLA02 User Manual

White LED driver for display backlight
Features
■ Boost DC-DC converter
■ Drives up to 6 LEDs with a total current up to 20
mA
■ Input voltage range 2.5 V to 18 V
■ Output current control
■ 2.3 MHz switching frequency
■ PWM input for the output current dimming with
300:1 dimming range
■ 350 mA integrated switch
■ Overvoltage protection
■ Chip overtemperature detection and protection
■ Soft-start implemented
■ Package DFN6 2 x 2 mm
STLA02
DFN6 (2 x 2 mm)
on/off by the logic signal connected to the EN pin and this pin is also dedicated for the PWM dimming of the output current. Current mode control of the regulation allows a fast response to a change of the enable pin voltage level.
Applications
■ PDA and handheld devices
■ Cellular phones
■ MP3 players
Description
STLA02 is a boost converter that operates from
2.5 V to 18 V and can provide an output voltage as high as 27 V and can drive up to 6 white LEDs connected in series. The total output current capability is 20 mA at an output voltage of 24 V. The total output power capability is up to 500 mW. The regulation is done by the internal error amplifier which works with the feedback voltage from the sensing resistor connected in high side sensing configuration. The device can be turned

Table 1. Device summary

Part number Order code Package
STLA02 STLA02PUR DFN6 (2 x 2 mm)
February 2011 Doc ID 010005 Rev 1 1/23
www.st.com
23
Contents STLA02
Contents
1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1 PWM input (EN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2 Selection of the external components . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2/23 Doc ID 010005 Rev 1
STLA02 Diagram

1 Diagram

Figure 1. Block diagram
VIN
EN/
EN/ PWM
PWM
12 V/5 V
12 V/5 V CONV
CONV
ILIM
ILIM
VIN
BIAS
BIAS
REFERENCE
REFERENCE
LOGIC
LOGIC
VSET
VSET
VBG
VBG
OVP
OVP
VBG
VBG
STEP-UP
STEP-UP CONTROL
CONTROL
ILIM
ILIM
VLX
VLX
FB SENSING
FB SENSING
VSET
VSET
VOUT
VOUT
FB
FB
GND
GND
AM07827v1
AM07827v1
Doc ID 010005 Rev 1 3/23
Pin configuration STLA02

2 Pin configuration

Figure 2. Pin connections (top view)

Table 2. Pin description

Pin n° Symbol Name and function
1V
IN
Supply voltage pin
2 GND Ground
3 LX Switching pin
4V
OUT
Output voltage pin
5 FB Feedback voltage
6 EN/PWM Enable pin or PWM control input for dimming
Exposed pad GND Ground
4/23 Doc ID 010005 Rev 1
STLA02 Maximum ratings

3 Maximum ratings

Table 3. Absolute maximum ratings

Symbol Parameter Value Unit
V
IN
V
LX
FB Feedback connection
Signal supply voltage - 0.3 to 19 V
Inductor connection - 0.3 to 30 V
(1)
- 0.3 to 30 V
EN/PWM Logic pin/PWM input - 0.3 to 12 V
V
OUT
P
TOT
T
OP
T
J
T
STG
1. The maximum acceptable difference between the V
Output voltage connection - 0.3 to 30 V
Continuous power dissipation (at TA = 70 °C)
(1)
530 mW
Operating ambient temperature range - 40 to 85 °C
Junction temperature - 40 to 150 °C
Storage temperature range - 65 to 150 °C
pin potential and feedback pin potential is 5 V.
OUT
Note: Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these conditions is not implied.

Table 4. Thermal data

Symbol Parameter Value Unit
R
thJA
1. Power dissipation is dependent on PCB. The recommended PCB design is included in this document (TBD).
Thermal resistance junction-ambient
(1)
102 °C/W

Table 5. ESD

Symbol Parameter Value Unit
HBM Human body model 2 kV
MM Machine model 200 V
Doc ID 010005 Rev 1 5/23
Application STLA02

4 Application

Figure 3. Application schematic

L
L
VLX
V
V
IN
IN
C
C
IN
IN
EN/PWM
EN/PWM
VIN
VIN
STLA02
STLA02
EN/PWM
EN/PWM
GND
GND
VLX
VOUT
VOUT
FB
FB
R
R
FB
FB
I
I
LED
LED
C
C
OUT
OUT
AM07828v1
AM07828v1

Table 6. List of external components

Component Manufacturer Part number Value Size
C
C
IN
OUT
MURATA GRM216R61E105KA12 1 µF / 25 V 0805
MURATA GRM216R61E105KA12 1 µF / 25 V 0805
MURATA LQH3NPN100NJ0L 10 µH 3x3x0.9 mm
L
TDK VLF3012ST-100MR59 10 µH 3x2.8x1.2 mm
R
FB
TYCO CPF0402B10RE 10 Ω 0402
LED OSRAM LWL283-Q1R2-3K8L-1-Z 20 mA / 3.1 V 0603
Note: Above listed components refer to a typical application with maximum performance settings.
Operation of the STLA02 is not limited to the choice of these external components.
6/23 Doc ID 010005 Rev 1
STLA02 Electrical characteristics

5 Electrical characteristics

V
= V
EN
T
= 25 °C, unless otherwise specified.
A

Table 7. Electrical characteristics

Symbol Parameter Test conditions Min. Typ. Max. Unit
= 3 V TA = - 40 °C to 85 °C unless otherwise specified. Typical values are at
IN
V
I
I
V
OUT
I
PEAK
V
I
FB
I
LX(leak)
ΔI
f
D
MAX
R
DSon
IN
S
O
FB
s
Input operating supply voltage
Supply current
Output current adjustment
Regulated voltage range V
Inductor peak current VIN = 2.5 V 300 400 550 mA
Feedback voltage (V VFB)
FB bias current V
N-MOS leakage current V
Output current tolerance VIN = 3 V, I
O
Switching frequency V
Maximum duty cycle V
-N Internal N-channel R
ν Efficiency of the chip itself
ν
OVP
Efficiency of the whole application
Output overvoltage protection
V
V
V
-
OUT
V
DSonILX
V V
V V
V
2.5 18 V
= VIN, V
EN
= GND 10 µA
EN
= 2.5 V to 18 V, R
IN
= 2.5 V to 18 V VIN+1 27 V
IN
= VIN, R
EN
= VIN, V
EN
= 0, V
EN
= 2.5 V, TA = 25 °C 1.7 2 2.3 MHz
IN
= VIN, V
EN
= 24 V, V
OUT
= 10 Ω 190 200 210 mV
FB
= 24 V, V
OUT
LX
OUT
= V
OUT
= 24 V 0.1 µA
OUT
= 0.2 V / R
= 24 V, V
= 23 V 2 4 mA
FB
= 10 Ω 20 mA
FB
= 24 V 6 µA
FB
FB
= 24 V 88 92 %
FB
-5 5 %
= 20 mA 0.8 Ω
= 10 V, IO = 20 mA, VO = 6 x
IN
FLED_max
IN
FLED_max
IN
+ V
RSENSE
= 24 V
= 10 V, IO = 20 mA, VO = 6 x
+ V
RSENSE
= 24 V
= 3 V, no load 28 V
(1)
(1)
85 %
83 %
T
SHDN
T
HYS
V
IL
V
IH
T
EN
T
RESPONSE
1. Guaranteed by design, but not tested in production.
Thermal shutdown 130 150 °C
Thermal shutdown hysteresis
Low and high level input logic signal on EN pin
LED current rise time I = 0 to I
LED
= 20 mA
LED current rise time I = 0 mA to I
LED
LED
LED
= 20 mA
= 2.5 V to 18 V, V
V
IN
V
= 9 V, V
IN
series
V
= 9 V, V
IN
series
Doc ID 010005 Rev 1 7/23
(1)
(1)
ENMAX
= 0 V to 3 V 6 LEDs in
EN
= 0 V to 3 V, 6 LEDs in
EN
, V
precharged
OUT
= 12 V
15 °C
01.5 V
1.8 V
IN
0.2 ms
60 µs
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