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STOD1812
Power supply for PMOLED display panel
Features

Synchronous step-up converter Input voltage range from 2.5 V to 5.5 V Maximum output current 120 mA Efficiency: 75 % at IO = 10 mA - 30 mA; 85 % at IO = 30 mA - 120 mA Switching at 1.2 MHz in typical application conditions Enable pin for shutdown mode True load disconnect Soft-start to limit inrush current UVLO protection Adjustable output voltage up to 20 V Low quiescent current: < 1 A in shutdown mode Over-temperature protection Package: DFN10L 3x3 mm, 0.8 mm Operating junction temperature range: -40 C to 125 C
DFN10L (3x3 mm)

Description
STOD1812 is a step-up converter designed to power passive matrix OLED (PMOLED) displays, providing the pre-charge and biasing voltage of the column matrix driver. STOD1812 uses a pulsed frequency modulation (PFM) control mode technique. The high switching frequency makes it possible to reduce the value and size of the external components. This device is particularly suitable for battery-operated applications, where overall system efficiency is the major concern. Synchronous rectification has been integrated in the device in order to eliminate the external Schottky diode. An internal compensation net is also integrated, enabling the STOD1812 to provide excellent load transient performance in addition to good load regulation. The output voltage is set using two external resistors. Over-temperature protection and undervoltage lockout (UVLO) functions are integrated in the device. An additional switch implements a true load disconnection feature which stops the currrent flowing from the input when the device is in shutdown mode. The EN pin turns off the device, reducing the quiescent current to 0.1 A.
Applications

Passive matrix OLED power supplies Mobile phones PDAs Camcorders Digital still cameras
Table 1.
Device summary
Order code STOD1812PUR Package DFN10L (3x3 mm) Packaging 3000 parts per reel
March 2008
Rev 1
1/19
www.st.com 19
Contents
STOD1812
Contents
1 2 3 4 5 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 5.2 5.3 5.4 Boost controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Under voltage lockout (UVLO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6 7 8 9 10
Typical application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Typical application performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2/19
STOD1812
Diagram
1
Figure 1.
Diagram
Internal block diagram
Figure 2.
Schematic diagram
3/19
Pin configuration
STOD1812
2
Figure 3.
Pin configuration
Pin connections (top view)
Table 2.
Pin n 1 2 3 4 5 6 7 8 9 10
Pin description
Symbol OUT OUT GND FB EN VI LX LX PGND PGND Exp Pad Output voltage Output voltage Ground Feedback DC supply voltage enable control pin. ON =VI. When pulled low put the device in shutdown mode. Input supply voltage. Switching node Switching node Power ground Power ground Exposed Pad. It must be connected to power ground Description
4/19
STOD1812
Maximum ratings
3
Table 3.
Symbol VI EN FB LX ILX VOUT PD TSTG TJ
Maximum ratings
Absolute maximum ratings
Parameter DC supply voltage Enable pin Feedback pin Switching node Switching current Converter output voltage Power dissipation Storage temperature range Operating temperature range Value -0.3 to 6 -0.3 to 6 -0.3 to 6 -0.3 to 20 Internally limited -0.3 to 20 Internally limited -65 to 150 -40 to 125 Unit V V V V A V mW C C
Table 4.
Symbol RthJA
Thermal data
Parameter Thermal resistance junction-ambient (tested on 2 layers board) Value 30.9 Unit C/W
Table 5.
Symbol ESD
ESD data
Parameter Human Body Model Value 2 Unit kV
5/19
Electrical characteristics
STOD1812
4
Table 6.
Electrical characteristics
Electrical characteristics (TJ = -40 C to 125 C, VI = 3.6 V, CI = CO = 4.7 F, L = 2.2 H, IO = 80 mA, VEN = VI, VO = 18 V, R1=270 k R2 = 20 k unless otherwise specified). ,
Parameter Test conditions Min. Typ. Max. Unit
Symbol Supply section VI IO UVLO_H UVLO_L
Supply input voltage Load current Under voltage lockout HIGH Under voltage lockout LOW
IO=0 to 120mA VI=2.5V to 5.5V
2.5 120 2.3 2.1 2.2 1.3 0.3 35 100 1.2
5.5
V mA
2.4
V V mA mA
IO=120mA No Load, Switching IQ Quiescent current VFB=VI - No Load, No Switching VEN =GND VEN H VEN L IEN Enable high threshold Enable low threshold Enable input current VI=2.5V to 5.5V VI=2.5V to 5.5V VEN=Vi
50 300
A nA V
0.4 500
V nA
Dynamic performance TON MAX TSS DMAX TON max time Soft-start time Maximum duty cycle Efficiency IO=5 to 30mA IO=30 to 120mA From enable to output regulation 0.5 0.6 95 75 85 s ms % % %
Step-up converter section VFB1 IFB VO_MAX Feedback voltage Feedback leakage current Output voltage range Static line regulation Static load regulation Line transient regulation Load transient regulation VI=2.5V to 5.5V VI=2.5V to 5.5V VI=2.5V to 5.5V; IO=0 to 120mA VI=2.5V to 5.5V, IO1=120mA, IO=0 to 120mA, VI=3.6V; VI=2.5V to 3.0V, IO1=120mA, TR=TF=50s TA=25C IO=5 to 120mA and IO=120 to 5mA, TR=TF=10s TA=25C, peak to peak 18 0.6 0.0016 80 250 1.18 1.21 30 1.24 100 V nA V %/V %/mA mV mV
VO_SLI VO_SLO VO_LIT VO_LOT
6/19
STOD1812 Table 6.
Electrical characteristics Electrical characteristics (continued) (TJ = -40 C to 125 C, VI = 3.6 V, CI = CO = 4.7 F, L = 2.2 H, IO = 80 mA, VEN = VI, VO = 18 V, R1=270 k R2 = 20 k unless otherwise specified). ,
Parameter Supply voltage rejection Inductor peak current Resistance on P-channel Resistance on N-channel Test conditions IO=5 to 120mA at 200Hz-Pulse 0.5VPP TDMA noise standard, TA=25C see Figure 14 TA=25C Min. Typ. 40 2.4 0.60 0.25 0.80 0.65 Max. Unit mV A
Symbol SVR IPK RDSONP RDSONN
Thermal shutdown OTP OTPHYST Over temperature protection Over temperature protection hysteresis 150 20 C C
7/19
Functional description
STOD1812
5
5.1
Functional description
Boost controller
STOD1812 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 feedback voltage, the boost switch tSW turns on and the inductor current ramps up. The inductor current is measured by detecting the temperature compensated drain voltage of the boost MOSFET. The boost turns off when its drain voltage reaches the internal reference, the main switch remains off until the minimum off time has passed and the feedback voltage is below the reference again. A maximum ON time prevents the switch tSW from staying ON for an excessively long period. In order to calculate the values of the bridge resistors with a fixed VO, the following formula can be used:
VO 1,21 R1 R2
-1=
5.2
Enable
The ENABLE pin is a logic input signal that turns on the controller when the voltage on this pin is equal to or higher than 1.2 V. When the voltage is at or below 0.4 V the STOD1812 goes into shutdown mode. In this case, the true-shutdown switch is turned off and the overall power consumption is reduced to 0.1 A. No pull-up or pull-down is present on this pin.
5.3
Efficiency
The total consumption of some PMOLED displays can be as low as 1 mA. In order to increase the battery life of the device, the STOD1812 offers high efficiency over a wide range of output load current and input voltages. See typical application efficiency performance in Section 8 on page 11.
5.4
Under voltage lockout (UVLO)
The minimum supply voltage is 2.5 V, under which the undervoltage lockout circuit operates with a typical threshold of 2.3 V.
8/19
STOD1812
Typical application information
6
Figure 4.
Typical application information
Typical application circuit connections
Table 7.
Symbol L CI CO R1 R2
External components
Parameter Inductor (ISAT = 2.5 A) Ceramic capacitor SMD Ceramic capacitor SMD Feedback resistor (for VO = 18 V) Feedback resistor (for VO = 18 V) Min. Typ. 2.2 4.7 4.7 270 20 Max. Unit H F F k k
Note:
The external components suggested in this document should be considered as a design reference guide. The performance data mentioned in the electrical characteristics table are not guaranteed for all the possible electrical parameters of the components included in this list. However, the operation of STOD1812 is not limited to the use of components included in this list.
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Demonstration board
STOD1812
7
Figure 5.
Demonstration board
Demonstration board photo
Figure 6.
Suggested demonstration board schematic (top layer view)
Figure 7.
Suggested demonstration board schematic (bottom layer view)
10/19
STOD1812
Typical application performance
8
Figure 8.
Typical application performance
(VO = 18 V, L = 2.2 H, CI = CO = 4.7 F, R1 = 270 k R2 = 20 k) , Efficiency vs output current Figure 9. Efficiency vs input voltage
100
VI = VEN = 3.6 V, IO = from 5 mA to 120 mA, T = 25C
100 90 Efficiency [%] 80 70 60 50 40
0 20 40 60 IO [mA] 80 100 120
VI = VEN = from 2.5 V to 5.5 V, IO = 120 mA, T = 25 C
90 Efficiency [%] 80 70 60 50 40
2.5
3
3.5
4 VI [V]
4.5
5
5.5
Figure 10. Efficiency vs temperature
Figure 11. Frequency vs temperature
100
80 70 60 50 40 -75 -50 -25 0 25 50 75 100 125 150 175
Frequency [MHz]
Efficiency [%]
90
VI = VEN = 3.6 V, IO = 120 mA
2.5 2.3 2.1 1.9 1.7 1.5 1.3 1.1 0.9 0.7 0.5 -75
VIN = VEN = 3.6 V, IO = 80 mA
T [C]
-50
-25
0
25
50 75 T [C]
100
125
150
175
Figure 12. Line transient
Figure 13. Load transient response
IO
VO
VI = from 2.5 V to 3 V, IO = 120 mA, VI (tRISE = tFALL) = 50s, T = 25 C
VI = 3.6 V, IO from 5mA to 120mA, tRISE = tFALL = 10 s, T = 25 C
11/19
Typical application performance
STOD1812
Figure 14. TDMA noise
VI=VINH
VO
VI = VINH = from 2.9 V to 3.4 V, IO = 120 mA, VI (tRISE) = 50 s, T = 25 C
12/19
STOD1812
Package mechanical data
9
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK(R) packages. These packages have a lead-free second level interconnect. The category of second Level Interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com.
13/19
Package mechanical data
STOD1812
Figure 15. DFN10L package outline
8049731/A
14/19
STOD1812
Package mechanical data
Table 8.
Dim.
DFN10L mechanical data
mm. Min. Typ. 0.75 0.02 0.20 0.18 2.90 2.23 2.90 1.49 0.25 3 2.38 3 1.64 0.50 0.30 0.40 0.50 0.012 0.30 3.10 2.48 3.10 1.74 0.007 0.114 0.088 0.114 0.059 Max. 0.80 0.05 Min. 0.028 0 inch. Typ. 0.030 0.001 0.008 0.010 0.118 0.094 0.118 0.065 0.020 0.016 0.020 0.012 0.122 0.098 0.122 0.069 Max. 0.031 0.002
A A1 A3 b D D2 E E2 e L
0.70 0
15/19
Package mechanical data
STOD1812
Tape & reel QFNxx/DFNxx (3x3) mechanical data
mm. Dim. Min. A C D N T Ao Bo Ko Po P 3.3 3.3 1.1 4 8 12.8 20.2 60 14.4 0.130 0.130 0.043 0.157 0.315 Typ. Max. 180 13.2 0.504 0.795 2.362 0.567 Min. Typ. Max. 7.087 0.519 inch.
16/19
STOD1812
Package mechanical data
Figure 16. DFN10L footprint - recommended data
17/19
Revision history
STOD1812
10
Table 9.
Date
Revision history
Document revision history
Revision 1 Initial release. Changes
25-Mar-2008
18/19
STOD1812
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