STOD2540 - STMicroelectronics

STOD2540
PMOLED display power supply
Features
■
Inductor switches boost controller
■
PFM mode control
■
High efficiency over wide range of load (1 mA
to 40 mA)
■
Integrated load disconnect switch
■
Over voltage protection with automatic restart
■
Soft start with adjustable peak current limit
■
Enable pin
■
Low shutdown current
■
Small external inductor
■
Supply voltage from 3.0 V to 5.5 V
In this state-of-the-art boost converter, a DC
current path exists between the battery source
and the load. In order to reduce the consumption
in shutdown mode, a high-side load isolation
switch is necessary to cut this DC current path in
standby mode. The load disconnect switch (LDS)
act as an isolation switch in shutdown mode.
Application
■
QFN8 (3 x 3 mm)
PMOLED display driver
Description
STOD2540 is dedicated to passive matrix OLED
(PMOLED) displays for portable handsets and
provides the pre-charge and biasing voltage of
the column matrix driver as shown in figure 3. The
current capability of STOD2540 allows feeding a
1", 1.3" or 1.5" color PMOLED. STOD2540 is a
boost converter that operates from 3.0 V to 5.5 V
and can provide an output voltage as high as 25
V. The output current capability is maximum 40
mA up to 25 V output voltage. The regulation is
performed by a resistor divider network (figure 3)
that detects the output voltage.
Table 1.
July 2010
Device summary
Order code
Package
Packaging
STOD2540PUR
QFN8 (3 x 3 mm)
3000 parts per reel
Doc ID 12204 Rev 10
1/20
www.st.com
20
Contents
STOD2540
Contents
1
Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5
Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6
5.1
Boost controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.2
Adjustable peak inductor current limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3
Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.4
OVP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.5
Load isolation switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.6
Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.7
Under voltage lockout (UVLO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1
Demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2/20
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STOD2540
Diagram
1
Diagram
Figure 1.
Block diagram
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Pin configuration
STOD2540
2
Pin configuration
Figure 2.
Pin connections (top through view)
Table 2.
Pin description
Pin n°
Symbol
1
VI
2
RSET
Peak inductor current adjust
3
AGND
Analog ground
4
FB
Feedback for the LED current regulation
5
VO
Output voltage for LED supply
6
VCAP
Load disconnect switch input
7
EN
IC enable signal
8
VSW
Boost switch drain
PGND
4/20
Note
Supply voltage
Power ground
Doc ID 12204 Rev 10
STOD2540
Maximum ratings
3
Maximum ratings
Table 3.
Absolute maximum ratings
Symbol
VBSW, VBO
VI
RSET
EN
Parameter
Value
Unit
Breakdown voltage at OUT and SW pin
40
V
Supply voltage range
6
V
RSET pin
VI + 0.3
V
Enable pin
VI + 0.3
V
2
kV
VESD
ESD ratings, HBM MIL STD 883C
TSTG
Storage temperature range
- 65 to 150
°C
TOP
Operating junction temperature range
- 40 to 85
°C
Value
Unit
52
°C/W
Table 4.
Symbol
RthJA
Thermal data
Parameter
Thermal resistance junction-ambient
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Electrical characteristics
4
STOD2540
Electrical characteristics
TJ = 40 °C to 85 °C, VI = 3.6 V, VEN = 3V, CI = CO = 4.7 µF, L = 4.7 µH, R1 = 180 kΩ,
R2 = 10 kΩ, VO = 24 V, Typ. values @ 25 °C, unless otherwise specified.
Table 5.
Electrical characteristics
Symbol
Parameter
VI
Input voltage range
VO
Regulated output voltage
VOVP
Over voltage protection on
output
IO
Continuous output current
ISD
Stand-by current
IQ
Quiescent current consumption
RDSON-SW
Boost switch RDSON (1)
Test condition
RDSON (1)
VI = 3 V to 5.5 V
Peak inductor limit range (1)
ILIM-MAX
VI + 0.5
25
Max.
Unit
5.5
V
35
V
35
VO = 25 V
V
1
40
VEN = Low, VI = 3.6 V
3
VEN = Low, VI = 3 V to 4.2 V
10
0.4
0.8
VI = 5.5 V @ 25 °C
0.8
1.2
VI = 4.2 V, ISW = 100 mA
0.4
mA
Ω
40
VO = 25 V, IO = 30 mA
V
Ω
2
40
RSET = 10 kΩ to 100 kΩ
mA
µA
VI = 3 V to 4.2 V @ 25 °C
BVDS Breakdown voltage
ILIM-ADJ
Typ.
3.0
BVDS Breakdown voltage
RDSON-LDS
Min.
V
0.2
1.1
A
Maximum peak inductor current V = 3 V to 5.5 V, R
I
SET = VI
0.75
1.2
A
FB
Feedback voltage
5% @ 25 °C
1.18
1.30
V
TON_MAX
Maximum ON time
VI = 4.2 V
5.5
µs
TOFF_MIN
Minimum OFF time
VI = 4.2 V
300
ns
(1)
Efficiency, VI = 3.6 V (1)
Eff
Efficiency, VI = 4.2 V (1)
Ripple
OVHYST
6/20
Output ripple and noise
IO = 1 mA to 5 mA
65
IO = 5 mA to 40 mA
70
IO = 1 mA to 5 mA
65
IO = 5 mA to 40 mA
70
1.24
%
VI = 3.6 V, IO = 5 mA, VO = 24 V
1.3
VI = 3.6 V, IO = 30 mA, VO = 24 V
1.3
VI = 4.2 V, IO = 5 mA, VO = 24 V
1.3
VI = 4.2 V, IO = 30 mA, VO = 24 V
1.3
Over-voltage hysteresis
%
2
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V
STOD2540
Table 5.
Electrical characteristics
Electrical characteristics (continued)
Symbol
Parameter
Test condition
Min.
Typ.
Max.
Unit
Enable input logic low
Disable Low VIL
Enable input logic high
Enable High VIH
Line_VFB
Line regulation VFB
VI = 3 V to 5.5 V, IO = 5 mA
5
35
mV
Load_VFB
Line regulation VFB
VI = 3 V to 5.5 V, IO = 5 mA
5
35
mV
VEN
0.3
V
1.2
1. Guaranteed by design.
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Functional description
STOD2540
5
Functional description
5.1
Boost controller
STOD2540 is a boost converter operating in PFM (pulsed frequency modulation) mode. The
converter monitors the output voltage through the bridge resistor divider R1 and R2 and
when the feedback voltage falls below the reference voltage, REF2, the boost switch tSW
turns ON and the current ramps up. The inductor current is measured by detect the
temperature compensated drain voltage of the boost MOSFET. The boost turns off when its
drain voltage reaches the reference REF1, the main switch remains off until the minimum off
time (300 ns typical) has passed and the feedback voltage is below the reference again. A
maximum ON time of 4 µs prevent the switch tSW to stay ON during a too long period of
time.
In order to well calculate the bridge resistors values with a fixed VO, the following formula
can be used:
(VO / 1.24) -1 = R1 / R2
5.2
Adjustable peak inductor current limit
The peak inductor current is monitored by sensing the drain voltage of the switch tSW.
Since it exceeds the temperature compensated and supply voltage compensated reference
REF1, the RS flip flop is reset and tSW is turned OFF.
By connecting a resistance between the pin RSET and GND, the peak current limit can be
adjusted from 200 mA to 1.1 A (RSET from 10 kΩ to 100 kΩ). When the pin RSET is directly
connected to VI, the default value is 1 A.
5.3
Enable
The ENABLE pin is a high logic input signal and allows turning on/off the controller without
cutting the input voltage from the boost regulator circuit. With a high input voltage (1.2 V <
VEN < VI + 0.3 V) on this pin, the device is allowed to work normally. No pull-up or pull down
is present on this pin.
5.4
OVP
If the regulation loop is cut, there is no signal at the feedback pin, the PFM controller will
then continue to switch without control and generate an output voltage at the SW, VCAP and
VO pin exceeding the breakdown value VBSW, VBCAP and VBO.
The over voltage protection (OVP) senses the voltage at the VCAP pin. When the voltage
exceed the breakdown voltage of the device the controller is automatically turned off.
A hysteresis control enables the device to automatically restart when the output voltage
drops below a 2 V typical value.
8/20
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STOD2540
5.5
Functional description
Load isolation switch
When the device is in shutdown mode, a DC current path always exists between the power
source and the load; increasing the standby consumption. A high side switch LDS isolates
the load from the source when the STOD2540 is disabled.
5.6
Efficiency
The total consumption of some PMOLED display, can be as low as 1 mA. In order to
increase the battery run time of the device, STOD2540 offers a high efficiency over a wide
range of load and input voltage range.
5.7
Under voltage lockout (UVLO)
The minimum supply voltage is 3.0 V, under this value the under voltage lockout circuit
operates with typical threshold 2.8 V.
When supply voltage is below 3.0 V, possible noise in the supply line could disturb the UVLO
circuit causing loss of output regulation. This behavior is eliminated choosing CI = 10 µF or
higher.
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Typical application
STOD2540
6
Typical application
Figure 3.
Basic connection
Table 6.
External components (see Figure 3)
Symbol
Parameter
Test
VRRM
D
Boost schottky diode
Min.
Typ.
30
VF at IF = 300 mA, TJ = 25 °C
0.5
V
IR at VR = 10 V, TJ = 25 °C
30
µA
Feedback resistor
180
R2
Feedback resistor
10
Peak current limit adjust
IPK = 200 mA to 1.1 A
CI
Input ceramic type low ESR
Ceramic type
CO
Output capacitance: ceramic
low ESR
L
10/20
10
kΩ
100
4.7
µF
Capacitance
4.7
µF
Voltage
42
V
ESR
1.6
W
Inductance
4.7
µH
1
A
Boost inductor (height < 2mm)
ISAT, RSET pin to VI
Note:
Unit
V
R1
RSET
Max.
The external components suggested in this document should be considered as a design
reference guide. The performances mentioned in the electrical characteristics table are not
guaranteed for all the possible electrical parameters of the components included in this list.
On other hand, the operation of STOD2540 is not limited to the use of components included
in this list.
Doc ID 12204 Rev 10
STOD2540
Typical application
6.1
Demonstration board
Figure 4.
Suggested demonstration board schematic (top layer view)
Doc ID 12204 Rev 10
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Typical performance characteristics
STOD2540
7
Typical performance characteristics
Figure 5.
TJ = 40 °C to 85 °C, VI = 3.6 V, VEN = 3 V, CI = CO = 4.7 µF, L = 4.7 µH, R1 = 180 kΩ,
R2 = 10 kΩ, VO = 24 V, Typ. values @ 25 °C, unless otherwise specified.
Efficiency vs. output current
Figure 6.
Efficiency vs. input voltage
Figure 7.
VEN vs. temperature
Figure 8.
Figure 9.
VFB vs. output current
Figure 10. VFB vs. output current
12/20
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VFB vs. input voltage
STOD2540
Typical performance characteristics
Figure 11. VOVP vs. temperature
Figure 12. VRIPPLE vs. input voltage
Figure 13. ILIM_MAX vs. input voltage
Figure 14. ILIM_MAX vs. temperature
Figure 15. ILIM_MAX vs. RSET
Figure 16. IQ vs. temperature
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Typical performance characteristics
STOD2540
Figure 17. tON_MAX vs. temperature
Figure 18. tOFF_MIN vs. temperature
Figure 19. Line VFB vs. temperature
Figure 20. Load VFB vs. temperature
14/20
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STOD2540
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.
Table 7.
QFN8 (3 x 3 mm) mechanical data
mm.
Dim.
Min.
Typ.
Max.
A
0.80
0.90
1.00
A1
0
0.02
0.05
A3
0.20
b
0.25
0.30
0.35
D
2.85
3.00
3.15
D2
2.49
2.64
2.74
E
2.85
3.00
3.15
E2
1.75
1.90
2.00
e
L
0.65
0.30
0.40
Doc ID 12204 Rev 10
0.50
15/20
Package mechanical data
STOD2540
Figure 21. Drawing dimension QFN8 (3 x 3 mm)
8057023_B
16/20
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STOD2540
Package mechanical data
Tape & reel QFNxx/DFNxx (3x3) 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
0.504
0.519
14.4
0.567
Ao
3.3
0.130
Bo
3.3
0.130
Ko
1.1
0.043
Po
4
0.157
P
8
0.315
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Max.
17/20
Package mechanical data
STOD2540
Figure 22. QFN8 (3x3) footprint recommended data
18/20
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STOD2540
Revision history
9
Revision history
Table 8.
Document revision history
Date
Revision
Changes
22-Mar-2006
1
Initial release.
03-Apr-2006
2
Add fig. 2 demonstration board on page 3.
08-Jun-2006
3
Description in cover page updated.
23-Jun-2006
4
Change range of RSET value and add description paragraph 5.7.
11-Sep-2006
5
Mistake on table 4 Ripple test value 3.6 V ==> 4.2 V.
27-Feb-2009
6
Modified mechanical data.
03-Mar-2009
7
Modified packaging Table 1 on page 1.
11-Mar-2009
8
Modified Figure 2 on page 4 and added Figure 22 on page 18.
25-Nov-2009
9
Modified Table 1 on page 1.
01-Jul-2010
10
Modified: Table 7 on page 15, Figure 21 on page 16 and Figure 22 on page 18.
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STOD2540
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