STLED25
5 channels step-up white LED driver
Datasheet − production data
Features
■
Operating input voltage range from 2.3 V to
5.5 V
■
± 7.5% LED current accuracy
■
Two LEDs in series per channel
■
High side current source
■
Up to 125 mA of total LED current
■
86% efficiency at 100 mA
■
PWM dimming with automatic shutdown time
window
■
2.5 MHz switching frequency
■
CSP 12 bumps 0.4 mm. pitch 1.4 x 1.8 mm.
continue operating driver channels that are
functioning normally, while avoiding excessive
power consumption or associated thermal issues.
The control technique is able to maintain the
efficiency close to 87% at medium load and
higher than 85% at light or full load. The device
also includes soft-start control, inrush current
limit, thermal shutdown and inductor peak current
limit. The STLED25 is packaged in a 12-bump
CSP (1.4 x 1.8 mm, 0.5 mm height).
Applications
■
LCD backlight with up to 10 LEDs
■
Cellular phones
■
PDAs
Flip-Chip 12 bumps (1.4 x 1.8 mm.)
Description
The STLED25 is a fixed frequency, high efficiency,
boost DC-DC converter with five parallel high side
current sources. It is capable of providing 125 mA
of total current with a maximum voltage of 7.5 V
on each channel. Each current source supports
single or dual LED connection. The output voltage
of the step-up converter is automatically set at
100 mV above the highest voltage required on
any driver, to guarantee proper operation of the
linear current sources. The device implements a
self-test feature to detect failure of any of the
LEDs and to disable the related channel. The
failure status is reset as soon the IC is disabled.
This mode of failure detection allows the device to
Table 1.
Device summary
Order code
Package
Packaging
STLED25JR
Flip-Chip12
Tape and reel
May 2012
This is information on a product in full production.
Doc ID 022323 Rev 3
1/30
www.st.com
30
Contents
STLED25
Contents
1
Application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5
Typical application performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1
Quiescent current consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.2
Switching frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.3
Continuous output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.4
Efficiency at 100 mA IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Efficiency at 75 mA IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.5
5.6
6
2/30
5.7
Efficiency at 50 mA IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Absolute channel accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.8
Current matching between LED strings . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.9
PWM dimming linearity 0.39 - 10% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.10
PWM dimming linearity 10 - 100% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.11
Inductor peak current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.12
Maximum continues output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1
Boost DC-DC converter operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2
Current setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.3
EN13 and EN45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.4
Modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.5
Undervoltage lockout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.6
Overtemperature protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.7
Open LED protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.8
Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.9
Short LED protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Doc ID 022323 Rev 3
STLED25
7
Contents
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1
7.2
External passive components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1.1
Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1.2
Input and output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Recommended PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
9
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Doc ID 022323 Rev 3
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Application schematic
1
STLED25
Application schematic
Figure 1.
STLED25 application schematic
Table 2.
Typical external components
Component
Manufacturer
Part number
Value
Size
CIN
Murata
GRM155R60J155M
1.5 µF
0402
COUT
Murata
GRM219R61A106ME47
10 µF
0805
L
Samsung
CIG21K4R7SCE
4.7 µH
0805
(1)
0402
RSET
25 k
1. For 20 mA per branch.
Note:
4/30
All the above components refer to a typical application. Operation of the device is not limited
to the choice of these external components.
Doc ID 022323 Rev 3
STLED25
Figure 2.
Application schematic
Functional block diagram
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Pin configuration
2
STLED25
Pin configuration
Figure 3.
Pin configuration (top view)
VIN
ISET
D1
EN13
EN45
D2
GND
D5
D3
SW
VOUT
D4
AM09921v1
Table 3.
6/30
Pin description
Pin name
Pin number
Description
VIN
A1
Supply from battery
ISET
A2
Resistor to GND from 1.28 V (typ.) internal reference: 390x current
multiplier
D1
A3
String 1 controlled by EN13
EN13
B1
Positive polarity. EN13 & 45 Low = IC shutdown
EN45
B2
Positive polarity. EN13 & EN45 Low = IC shutdown
D2
B3
String 2 controlled by EN13
GND
C1
Power ground and IC ground
D5
C2
String 5 controlled by EN45
D3
C3
String 3 controlled by EN13
SW
D1
Inductor connection to internal switch
VOUT
D2
DC-DC output to VOUT capacitor
D4
D3
String 4 controlled by EN45
Doc ID 022323 Rev 3
STLED25
3
Maximum ratings
Maximum ratings
Table 4.
Absolute maximum ratings
Symbol
Parameter
Value
Unit
VIN
Supply voltage
-0.3 to +6
V
SW
Switching node
-0.3 to + 11
V
VOUT
Output voltage
-0.3 to +10
V
D1-D5
LED strings
-0.3 to +10
V
EN13, EN45
Signal pins
-0.3 to VIN
V
Current setting
-0.3 V to 2
V
Machine model
± 200
Human body model
± 2000
Charged device model
± 500
ISET
ESD
TAMB
TJ
TSTG
Table 5.
Operating ambient temperature
Maximum operating junction temperature
Storage temperature
-30 to 85
°C
+150
°C
-65 to 150
°C
Thermal data
Symbol
RTHJA
V
Parameter
Junction to ambient thermal resistance
(1)
Value
Unit
62
°C/W
1. This parameter corresponds to a 4-layer PCB board with 1 inch² of cooling area.
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Electrical characteristics
4
STLED25
Electrical characteristics
- 30 °C < TA < 85 °C, VIN = 3.7 V; VOUT = 7.5 V, EN13 = EN45 = VIN, typical values are at
TA = 25 °C, unless otherwise specified.
Table 6.
Electrical characteristics
Symbol
Parameter
Test conditions
Min.
Typ.
Max.
Unit
2.3
3.7
5.5
V
µA
General section
VIN
Iq
Operating input voltage
Shutdown mode
EN13 = EN45 = 0
0.5
2
Undervoltage lockout
threshold
VIN rising
1.9
2.0
VUVLO
fSW
Switching frequency
IOUT
IPK
ν
νDC-DC
Continuous output current
VIN falling
(1)
V
1.7
1.8
2.25
2.5
VIN = 2.5 V, VOUT = 6.2 V
Inductor peak current
550
Application efficiency (1)
(VIN = 3.7 V; VOUT = 6.2 V;
see application schematic)
IOUT = 50 mA
84
IOUT = 75 mA
86
IOUT = 100 mA
86
DC-DC converter efficiency
IOUT = 100 mA
88
2.75
MHz
125
mA
650
mA
%
VOVP
Overvoltage protection
OVPHYST
Overvoltage protection
hysteresis
250
mV
Thermal shutdown
150
°C
Hysteresis
20
°C
TSHDN
8.8
9.05
9.3
V
LEDs current
ID1-D5
Current matching
VSCP
Short-circuit protection on
LEDs
ILED
ISET
VCSH
8/30
Absolute channel accuracy
-5.5
Measured on the Dx pins
+5.5
1.28
%
V
5 mA < ILED < 25 mA,
VIN = 2.5 V to 5.5 V
-7.5
+7.5
%
2.5 mA < ILED < 5 mA,
VIN = 2.5 V to 5.5 V
-10
10
%
Voltage reference
RSET = 200 k to 15 k
1.28
V
Current mirror
ILED / ISET
390
A/A
135
mV
Current source headroom
voltage
Doc ID 022323 Rev 3
STLED25
Table 6.
Electrical characteristics
Electrical characteristics (continued)
Symbol
IRIPPLE
Parameter
Test conditions
LED peak-to-peak current
ripple (1) (2)
Min.
Typ.
VIN = 2.5 V; ILED = 20 mA at
all channels,
EN13PWM = EN45PWM
500
VIN = 2.5 V; ILED = 20 mA at
all channels,
EN13PWM = EN45PWM
4000
1/255 PWM, 300 Hz, 20 mA
on all drivers, VIN = 2.5 V (3)
PWMLIN
PWM linearity(1) (2)
25/255 PWM, 300 Hz, 20
mA on all drivers, VIN = 2.5 V
Max.
Unit
µA
10
%
2
%
0.5
µA
(3)
ILED_LEAK
LED driver leakage in OFF
state
ILED_MAX
LED driver max current
Line_tr
Line transient response
VOUT = 7.5 V
25
(1)
VINTR=+/-350mV,10µs step
mA
30
%
fDIM
PWM dimming frequency
100
800
Hz
DDIM
Duty cycle of PWM dimming
0.39
100
%
Logic inputs
REN
Internal pull-down resistor
VIL
EN low-level input voltage
VIH
EN high-level input voltage
ILK-I
EN input leakage current
100
kΩ
VIN = 2.7 V to 4.5 V
0.68
VIN = 2.3 V to 5.5 V
0.55
V
VIN = 2.7 V to 4.5 V
1.07
VIN = 2.3 V to 5.5 V
1.14
VEN = VIN = 4.2 V, 100 k
internal pulldowns
V
42
µA
Power switches
RDSON
ILKG-LX
P-channel on resistance
880
N-channel on resistance
450
mΩ
LX leakage current
VIN=VLX=4.8V; VEN=0
1
µA
1. Not tested in production
2. 10% value reduction at VIN = 2.3 V
3. The PWM linearity is measured on the mean value of the output current in PWM mode in the 100 ms window. The
frequency of the PWM is 300 Hz
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Typical application performance
STLED25
5
Typical application performance
5.1
Quiescent current consumption
Figure 4.
Quiescent current at different ambient temperatures
AM09922v1
0.06
IQ [µA]
0.05
0.04
-30°C
0.03
25°C
0.02
85°C
0.01
0
1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9
VIN [V]
5.2
Switching frequency
Switching frequency at different ambient temperatures
FSW [MHz]
Figure 5.
AM09923v1
2.7
2.65
2.6
2.55
2.5
2.45
2.4
2.35
2.3
1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9
VIN [V]
10/30
Doc ID 022323 Rev 3
-30°C
25°C
85°C
STLED25
5.3
Typical application performance
Continuous output current
IOUT [mA]
Figure 6.
Output current when VOUT = 8.5 V at different ambient temperatures
110
100
90
80
70
60
50
40
30
20
10
0
AM09924v1
-30°C
25°C
85°C
1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9
VIN [V]
Efficiency at 100 mA IOUT
Figure 7.
Efficiency when IOUT = 100 mA at different ambient temperatures
AM09925v1
100
90
η [%]
5.4
80
-30°C
25°C
70
85°C
60
50
1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9
VIN [V]
Doc ID 022323 Rev 3
11/30
Typical application performance
5.5
STLED25
Efficiency at 75 mA IOUT
Figure 8.
APPL efficiency when IOUT = 75 mA at TA = 25 °C
AM09926v1
100
η [%]
90
80
70
60
50
1.7
2.1
2.5
2.9
3.3
3.7
4.1
4.5
4.9
5.3
5.7
VIN [V]
5.6
Efficiency at 50 mA IOUT
Figure 9.
APPL efficiency when IOUT = 50 mA at TA = 25 °C
AM09927v1
100
η [%]
90
80
70
60
50
1.7
2.1
2.5
2.9
3.3
3.7
VIN [V]
12/30
Doc ID 022323 Rev 3
4.1
4.5
4.9
5.3
5.7
STLED25
Typical application performance
5.7
Absolute channel accuracy
Figure 10. Absolute channel accuracy - set string current to 20 mA
2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 5.7 5.9
5
4
3
I DEV [%]
2
1
0
-1
-2
-3
-4
-5
5.8
VIN [V]
AM09928v1
-30°C-ID1
-30°C-ID2
-30°C-ID3
-30°C-ID4
-30°C-ID5
25°C-ID1
25°C-ID2
25°C-ID3
25°C-ID4
25°C-ID5
85°C-ID1
85°C-ID2
85°C-ID3
85°C-ID4
85°C-ID5
Current matching between LED strings
Figure 11. Current matching - set string current to 20 mA
2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 5.7 5.9
4
-30°C-ID1
-30°C-ID2
3
-30°C-ID3
-30°C-ID4
2
-30°C-ID5
25°C-ID1
IDEV [%]
1
25°C-ID2
25°C-ID3
0
25°C-ID4
-1
25°C-ID5
85°C-ID1
-2
85°C-ID2
85°C-ID3
-3
85°C-ID4
85°C-ID5
-4
VIN [V]
Doc ID 022323 Rev 3
AM09929v1
13/30
Typical application performance
5.9
STLED25
PWM dimming linearity 0.39 - 10%
IOUT [mA]
Figure 12. PWM linearity 0.39 - 10% at TA = 25 °C
11
10
9
8
7
6
5
4
3
2
1
0
0.00
AM09930v1
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00 10.00 11.00
DC [%]
5.10
PWM dimming linearity 10 - 100%
IOUT [mA]
Figure 13. PWM linearity 10 - 100% at TA = 25 °C
110
100
90
80
70
60
50
40
30
20
10
0
AM09931v1
0
10
20
30
40
50
60
DC [%]
14/30
Doc ID 022323 Rev 3
70
80
90
100
110
STLED25
5.11
Typical application performance
Inductor peak current
IL [mA]
Figure 14. Inductor peak current at TA = 25 °C
650
600
550
500
450
400
350
300
250
200
150
100
50
0
1.5
AM09932v1
1.9
2.3
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
5.9
VIN [V]
Maximum continues output current
Figure 15. Maximum output current at TA = 25 °C
IOUT [mA]
5.12
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
AM09933v1
25kOhm/100mA
20kOhm/125mA
15kOhm/170mA
1.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 5.9
VIN [V]
Doc ID 022323 Rev 3
15/30
Typical application performance
Figure 16. Startup waveform
STLED25
Figure 17. Line transient response
Figure 18. Line transient response
16/30
Doc ID 022323 Rev 3
STLED25
6
Detailed description
Detailed description
The STLED25 is a high efficiency white LED power supply which integrates a step-up
converter and 5 high-side current sources. The device is controlled by two enable inputs
called EN13 and EN45 according to the labels of the LED channels. EN13 enables LED
channels 1, 2, 3 and EN45 enables LED channels 4, 5. The device is protected against
shorted LED channels by short LED protection and against open LED channels by open
LED protection. The device is able to recognize which channel has failed, and switch off this
channel to maintain correct operation of the remaining channels. The STLED25 device is
125 mA total output current capable and works over a battery voltage range of 2.3 V to 5.5
V. The typical output voltage during operation corresponds to the voltage level equal to
VFLED + 125 mV. The STLED25 device has an optimized switching power bridge to reach a
high level of application efficiency (86%) with the typical battery voltage of 3.7 V. The device
is also able to work at high efficiency when not all the LED channels of the device are used.
6.1
Boost DC-DC converter operation
The step-up bridge with current mode control of the regulation regulates the output voltage
level according to the LED channel with the highest VFLED, in order to maintain sufficient
voltage headroom for the related current sources. The typical headroom of the current
sources is in the range of 135 mV. The STLED25 contains a current limiter, with a typical
value 600 mA, and soft-start control to limit the supply current from the battery. The method
of regulation during startup and normal operation is explained in Section 6.4.
6.2
Current setting
Each LED channel regulates to the same current. The value of the LED current is set by
choosing the RSET resistor. The current flowing through this resistor is mirrored in order to
obtain the LED current. The multiplication factor is 390.
The LED current is calculated with the following formula:
Equation 1
ILED =
VSET
× 390
RSET
where:
VSET = 1.28 V typical
6.3
EN13 and EN45
EN13 and EN45 play the dual role of enable pin and PWM dimming. EN13 drives strings
D1, D2, D3 while EN45 drives D4 and D5. Both EN13 and EN45 are pulled down internally
by 100 k resistors.
The EN pins accept a signal between 100 Hz and 800 Hz, at duty cycles from 0.39% to
100%. The output average current maximum error is 10% at 0.39%, PWM duty cycle at 300
Hz.
Doc ID 022323 Rev 3
17/30
Detailed description
6.4
STLED25
Modes of operation
Shutdown mode
The device is in shutdown with minimum current consumption. It goes to PWM_start as
soon as EN13 or EN45 are pulled high.
PWM_start
Once ENxx is asserted, the DC-DC is turned ON with a soft-start procedure until VOUT
reaches 7 V; this phase takes around 1.2 ms.
If ENxx remains asserted, the device will stay in this condition and wait for 10 ms
(PWM_start_up), then the STLED25 goes to PWM_normal mode. If the next EN is asserted
during the PWM_start_up mode, the device will immediately enable the LED current
sources and continue in PWM_normal mode.
PWM_normal
In this mode of operation the drivers are in the ON state delivering current to the LEDs, and
the DC-DC converter maintains the VOUT value with enough headroom to keep the high side
current sources in regulation.
When both EN pins are low, the drivers are turned off and the RUN_HOLD timer starts.
RUN_hold
The RUN_hold time lasts approximately 30 ms. During this time, the DC-DC converter
maintains the last optimum voltage on VOUT. If RUN_hold time elapses without EN
reassertion, then the STLED25 goes into shutdown mode. If EN is reasserted, the device
goes to PWM_normaL mode.
Figure 19. Modes of operation
18/30
Doc ID 022323 Rev 3
STLED25
6.5
Detailed description
Undervoltage lockout
The undervoltage lockout function prevents improper operation of the STLED25 when the
input voltage is not high enough. When the input voltage is below the UVLO threshold, the
device is in shutdown mode. The hysteresis of 100 mV prevents unstable operation when
the input voltage is close to the UVLO threshold.
6.6
Overtemperature protection
An internal temperature sensor continuously monitors the IC junction temperature. If the IC
temperature exceeds 150 °C (typical), the device stops operating. As soon as the
temperature falls below 135 °C (typical), normal operation is restored.
6.7
Open LED protection
The device is able to detect an “Open LED” failure in each LED channel independently.
When this failure appears, the DC-DC increases the output voltage to maintain the current
source headroom voltage until the OVP threshold is reached; the device detects which LED
channel is the root cause and switches off this LED channel. This state is maintained until
the STLED25 goes into shutdown mode.
6.8
Overvoltage protection
The device has overvoltage protection on the VOUT pin to protect the device and external
components against the high voltage coming from the DC-DC, in case of a disconnected
load. When the output voltage level reaches the OVP threshold (9.3 V typical), the DC-DC is
turned off until the output voltage level goes below the OVP threshold. The hysteresis of the
OVP threshold is approximately 250 mV.
6.9
Short LED protection
The device is able to detect a shorted LED in each LED channel independently; when the
protection detects a failure on any of the LED channels, it switches off this channel until the
STLED25 enters shutdown mode.
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Application information
STLED25
7
Application information
7.1
External passive components
7.1.1
Inductor selection
The inductor is the key passive component for switching converters.
For the STLED25, an inductance of 4.7 µH is recommended. It is very important to select
the right inductor according to the maximum current the inductor can handle to avoid
saturation. The peak current for the step-up can be calculated with the following formula:
Equation 2
IPEAK − BOOST =
VOUT × IOUT
VIN MIN × ( VOUT − VIN MIN )
+
η × VIN MIN
2 × VOUT × fs × L
where:
VOUT: step-up output voltage. The boost control loop keeps it 135 mV higher than the
maximum among VD1-D5
IOUT: total output current
VIN: input voltage of STLED25
fs: switching frequency. Use the minimum value of 2.25 MHz for the worst case
η: efficiency of step-up converter. It is 0.87 at 75 mA load
Table 7.
List of recommended inductors
Manufacturer
Part number
Inductance
[µH]
Saturation current [A]
Size [mm]
Samsung
CIG21K4R7SCE
4.7
0.6
0805
Murata
LQM21PN4R7
4.7
0.6
0805
7.1.2
Input and output capacitor selection
It is recommended to use ceramic capacitors with low ESR as input and output capacitors in
order to filter any disturbance present in the input line and to maintain stable operation of the
step-up converter. A minimum real capacitance value of 1 µF must be guaranteed for CIN
and 4.2 µF COUT in all conditions.
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STLED25
Table 8.
Application information
Input and output capacitor
Part number
Nominal
capacitance [µF]
Rated voltage [V]
Murata
GRM155R60J155M
1.5
6.3
0402
Samsung
CL05A225MQ5NSKC
2.2
6.3
0402
GRM219R61A106ME47
10
10
0805
Manufacturer
TCC
Size [mm]
CIN
COUT
Murata
7.2
Recommended PCB layout
The STLED25 is a high-frequency power switching device, so it requires a proper PCB
layout in order to obtain the necessary stability and optimize line/load regulation and output
voltage ripple. Input and output capacitors must be as close as possible to their relative pins.
Figure 20. Top layer
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Application information
STLED25
Figure 21. Mid layer 1
Figure 22. Mid layer 2
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STLED25
Application information
Figure 23. Bottom layer
Figure 24. Top overlay
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Application information
STLED25
Figure 25. Photo of the application board
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8
Package mechanical data
Package mechanical data
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK® is an ST trademark.
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Package mechanical data
STLED25
Flip-chip 12 mechanical data
mm.
Dim.
Min.
Typ.
Max.
A
0.45
0.50
0.55
A1
0.17
0.20
0.23
A2
0.28
0.30
0.32
b
0.22
0.26
0.30
D
1.815
1.845
1.875
D1
E
1.20
1.358
1.388
E1
1.418
0.80
e
0.36
0.40
0.44
fD
0.313
0.323
0.333
fE
0.284
0.294
0.304
ccc
0.05
8116384-D
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Package mechanical data
Tape & reel Flip-Chip 12 mechanical data
mm.
inch.
Dim.
Min.
Typ.
A
Max.
Min.
Typ.
180
13.2
7.087
C
12.8
D
20.2
0.795
N
60
2.362
T
Max.
0.504
0.520
14.4
0.567
Ao
1.46
1.51
1.56
0.057
0.059
0.061
Bo
1.89
1.94
1.99
0.074
0.076
0.078
Ko
0.54
0.59
0.64
0.021
0.023
0.025
Po
3.9
4.1
0.154
0.161
P
3.9
4.1
0.154
0.161
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Package mechanical data
STLED25
Figure 26. Footprint recommended data (mm.)
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9
Revision history
Revision history
Table 9.
Document revision history
Date
Revision
Changes
10-Oct-2011
1
Initial release.
13-Dec-2011
2
Modified: COUT part number Table 2 on page 4 and Table 8 on
page 21.
11-May-2012
3
Document status promoted from preliminary data to production data.
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STLED25
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