STMicroelectronics Inverting and step-up DC-DC converter Datasheet
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STOD1412
Inverting and step-up DC-DC converter
Features
■
■
■
■
2.7 V to 5.5 V input voltage range
120 mA max output current for each converter
Output voltages:
– Step-up from 4.3 V to 6.0 V
– Inverting from - 8.0 V to - 2.0 V
Synchronous rectification for both DC-DC converters
QFN16L (3 x 3 mm)
■ Efficiency:
– 80% I
O
= 10 mA - 30 mA
– 85% I
O
= 30 mA - 120 mA
1.3 MHz PWM mode control
Description
■
■
■
■
■
■
Shutdown mode with enable pin
Inrush current protection
Adjustable output voltages
True shutdown mode
The STOD1412 is a dual DC-DC converter capable of producing a positive and negative output voltage from a positive input voltage ranging from 2.7 V to 5.5 V. It integrates two complete power stages, one step-up and one inverting, each of which need just one inductor, and input and output capacitor.
Less than 1 µA current consumption in shutdown mode
■
■
■
Overtemperature protection
Package: 16-pin QFN 3 x 3 mm
Temperature range: - 40 °C to 85 °C
Applications
The STOD1412 works in PWM mode, switching at a 1.3 MHz frequency, thus reducing the size and values of external components. An enable pin makes it possible to turn off the device to reduce the quiescent current to less than 1 µA. The output voltages can be set easily by using two external resistors for each converter.
■
■
■
Active matrix organic LED power supplies
Mobile phones
PDAs
The device integrates a “soft-start” with controlled inrush current limit, thermal shutdown and shortcircuit protection.
Camcorders
High efficiency and low quiescent current, ■
■
Digital still cameras combined with the small number and tiny size of
Obsolete Product(s) - Obsolete Product(s) suitable for battery-operated systems, particularly for powering active matrix OLED display panels.
Table 1.
Device summary
Order code
STOD1412PMR
Package
QFN16L (3 x 3 mm)
Packaging
4500 parts per reel
March 2010 Doc ID 13860 Rev 2 1/20
www.st.com
20
STOD1412 Contents
Contents
STOD1412 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Obsolete Product(s) - Obsolete Product(s)
2/20 Doc ID 13860 Rev 2
STOD1412
1 STOD1412 block diagram
Figure 1.
Block diagram
STOD1412 block diagram
Obsolete Product(s) - Obsolete Product(s)
Doc ID 13860 Rev 2 3/20
STOD1412 Pin configuration
Figure 2.
Pin connections (top view)
Table 2.
Pin n°
Pin description
Symbol Description
1
2
3
4
5
6
V
O1
TRIM
TRIM
TRIM
FB1
V
REF
Step-up converter output voltage.
Trimming pin. This pin must be left floating.
Trimming pin. This pin must be left floating.
Trimming pin. This pin must be left floating.
Feedback pin of the step-up converter.
External voltage reference. A C
REF
= 100 nF ceramic capacitor must be connected to this pin.
Signal ground pin. This pin must be connected to PGND pin.
Feedback pin of the inverting converter.
7
8
GND
FB2
9
10
11
12
V
I
EN
TRIM
V
CC
Lx2
Input supply voltage.
Enable control pin. ON = V
I
. When pulled low the device goes into shutdown mode.
Trimming pin; this pin must be left floating.
Power input supply voltage.
13 Switching node of the inverting converter.
14 Inverting converter output voltage.
V
O2
PGND Power ground pin.
15 Obsolete Product(s) - Obsolete Product(s)
16 Lx1 Switching node of the step-up converter.
Exp pad Exposed pad. This pin must be connected to V
O2.
4/20 Doc ID 13860 Rev 2
STOD1412
3 Maximum
Table 3.
Symbol
Absolute maximum ratings
Parameter
V
I
, V
CC
EN
ILx
2
Lx
2
V
O2
FB
2
FB
1
V
O1
Lx
1
ILx
1
V
REF
P
D
X
T
J
DC supply voltage
Enable pin
Switching current of the converter
Inverting converter switching node
Inverting converter output voltage
Inverting converter feedback pin
Step-up converter feedback pin
Step-up converter output voltage
Step-up converter switching node
Step up converter’s switching current
Reference voltage
Power dissipation
Storage temperature range
Operating junction temperature range
Table 4.
Symbol
R thJA
Thermal data
Parameter
Thermal resistance junction-ambient
Maximum ratings
Value
-0.3 to 6
-0.3 to 6
Internally limited
-10 to V
I
+0.3
F10 to GND+0.3
-1 to +1
-0.3 to V
I
+0.3
-0.3 to 6
-0.3 to OUT
1
+0.3
Internally limited
-0.3 to 3
Internally limited
-65 to 150
-40 to 85
Unit
V mW
°C
°C
V
V
A
V
V
V
V
V
V
A
Value
49
Unit
°C/W
Obsolete Product(s) - Obsolete Product(s)
Doc ID 13860 Rev 2 5/20
Electrical characteristics STOD1412
Table 5.
Symbol
T
J
= 25 °C, V
µH, L2 = 6.8 µH, I
R
2
I
= V
CC
= 3.7 V, C
I
= 2.2 µF, C
O1,2
- I
O2
= 30 mA, V
EN
= 4.7 µF, C
3
= 1 µF, C
REF
= 100 nF, L1 = 4.7
= V
I
, V
O1
= -6.4 V, R
1
= 470 k
Ω,
=166 k
Ω, R
O1,2
= I
O1
3
= 533 k
Ω, R
= 4.6 V, V
O2
4
= 100 k
Ω, unless otherwise specified.
Electrical characteristics
Parameter Test condition
Supply section
V
I
Supply input voltage
Operating input voltage range
UVLO_H Undervoltage lockout HIGH VCC
UVLO_L Undervoltage lockout LOW
I_V
I
Q
I
Input current
Quiescent current
V
EN
H Enable high threshold
V
EN
L Enable low threshold
I
EN
Enable input current
Dynamic performance
V
FB1
=1.3 V, V
FB2
= -0.5 V (no switching)
No Load
V
EN
=GND
V
I
=2.7 V to 4.5 V
V
I
=2.7 V to 4.5 V
V
EN
=V
I
Freq.
Frequency
D1
MAX
D2
MAX
Maximum duty cycle
Maximum duty cycle
Total system efficiency
No load
No load
I
O1,2
=10 to 30 mA, V
O1
=4.6 V,
V
O2
= -6.4 V
I
O1,2
=30 to 120 mA, V
O1
=4.6 V,
V
O2
= -6.4 V
Step-up converter section
V
FB1
Feedback voltage on stepup
(1)
V
I
=2.7 V to 4.5 V
Δ
Δ
Δ
Δ
Δ
V
V
V
V
V
O1
O1
O1
O1
O1
Static line regulation
Static load regulation
Static load regulation
Load transient regulation
V
I
=2.7 V to 4.2 V, I
O1
=5 mA, I
O2
no load, T
J
= -40°C to 85°C
V
I
=2.7 V to 4.2 V, I
O1
=100 mA, I
J
= -40°C to 85°C
O2
I
O1
=5 to 100 mA, I
O2
no load, V
I
=2.7 V,
T
J
= -40°C to 85°C
I
O1
T
J
=5 to 100 mA, I
= -40°C to 85°C
O2
no load, V
I
=4.2 V,
I
O1
T
R
=3 to 30 mA and I
=T
F
=30 µs
O1
=30 to 3 mA,
Min.
2.7
2.7
1.2
Typ.
Max.
Unit
2.55
2.5
0.5
3.5
1.3
90
90
80
85
1.20
2
2
2
2
5.5
4.5
1
1
0.6
1
20
V
V
V mA
µA
V
µA
MHz
%
%
%
V
%
%
%
% mV
6/20 Doc ID 13860 Rev 2
STOD1412 Electrical characteristics
Table 5.
Symbol
Electrical characteristics (continued)
Parameter Test condition
Δ
Δ
V
V
O1
O1
Load transient regulation
Ripple output voltage range
I
O1
=10 to 100 mA and I
O1
=100 to 10 mA, T
R
=T
F
=30 µs
I
O1
=5 to 100 mA @ Low frequency typ.=20 kHz
I
O1
I-L
1MAX
R
DSON
P1
R
DSON
N1
Step-up range load current
I peak current
Inverting converter section
V
O1
below 10% of nominal value
Min.
Typ.
Max.
Unit
0.9
1.10
0.85
30
20
120 mV mV
V
Δ
Δ
Δ
Δ
Δ
Δ
Δ
FB2
V
V
V
V
V
V
V
O2
O2
O2
O2
O2
O2
O2
Feedback voltage on inverting
(1)
V
I
=2.7 V to 4.5 V
Static line regulation
Static line regulation
Static load regulation
Static load regulation
Load transient regulation
Load transient regulation
Ripple output voltage range
V
I
=2.7 V to 4.2 V, I
O2
=5 mA, I
O1
no load, T
J
= -40°C to 85°C
V
I
=2.7 V to 4.2 V, I
O2
=100 mA, I
O1
no load, T
J
= -40°C to 85°C
I
O2
=5 to 100 mA, I
O1
no load, V
I
=2.7 V,
T
J
= -40°C to 85°C
I
O2
T
J
=5 to 100 mA, I
= -40°C to 85°C
O1
no load, V
I
=4.2 V,
I
O2
T
R
=3 to 30 mA and I
=T
F
=30 µs
O2
=30 to 3 mA,
I
O2
=10 to 100 mA and I
O2
=100 to 10 mA, T
R
=T
F
=30 µs
I
O2
=5 to 100 mA @ Low frequency typ.=20 kHz
I
O2
I-L
2MAX
R
DSON
P2
Inverting range load current
I peak current V
O2
below 10% of nominal value
R
DSON
N2
V
REF
Voltage reference
I
REF
Voltage reference current capability
I
REF
V
=10 µA
REF
= 1.192 V 100
-0.5
2
2
2
2
50
100
20
-120
-1
0.63
0.65
1.192
1.209
1.228
mV
Thermal shutdown
Obsolete Product(s) - Obsolete Product(s)
OTP Overtemperature protection 140 °C
OTP
HYST
Overtemperature protection hysteresis
15 °C
1.
Guaranteed by design.
2. The tolerance of external components is not included.
%
%
%
% mV mV mV mA
A
Ω
Ω
V
µA mA
A
Ω
Ω
Doc ID 13860 Rev 2 7/20
Introduction STOD1412
The STOD1412 is a dual DC-DC converter which produces one positive and one negative output voltage that are each independently regulated and the values of which can be adjusted with external resistors. Each DC-DC converter is able to supply up to 120 mA of current with input voltages ranging from 2.7 V and 5.5 V. The device uses a fixed-frequency
PWM controller at 1.3 MHz. This control scheme simplifies noise filtering in sensitive applications and provides excellent line regulation.
The operation of the STOD1412 can be best understood by referring to the block diagram in
, where the step-up control circuit is shown, and a similar scheme is adopted for the
inverting section. At the start of each oscillator cycle, the SR latch is set, which turns on power switch SW1. A voltage proportional to the switch current is added to the sawtooth ramp and the resulting sum is fed into the positive terminal of the PWM comparator A2.
When this voltage exceeds the level of the negative input of A2, the SR latch is reset, thus turning off the power switch. The voltage level of the negative input of A2 is set by the error amplifier A1, and it is simply an amplified version of the difference between the feedback voltage and the reference voltage. In this manner, the error amplifier sets the correct peak current level necessary to keep the output in regulation. If the error amplifier output increases, more current is delivered to the output; if it decreases, less current is delivered.
The device also has a current limit circuit (not shown in
constantly monitored and not allowed to exceed the preset maximum switch current (IL
1
max, IL
2
-max). If the switch current reaches this value, the SR latch is reset regardless of the state of comparator A2. This current limit helps to protect the power switch as well as the external components connected to the device.
The step-up converter works in continuous mode detector (CMD) in the entire line and load range, while the inverting converter can work in both discontinuous mode detector (DMD) and CMD.
Figure 3.
PWM control scheme
Obsolete Product(s) - Obsolete Product(s)
8/20 Doc ID 13860 Rev 2
STOD1412
5.1
Introduction
Setting output voltage
The output voltage can be set using external network resistors.
The positive output voltage range is 4.3 V minimum up to a maximum of 6.0 V. It is obtained by connecting FB1 to OUT1 through R
2
, and FB1 to PGND through R
1
(see
). The positive output value can be calculated using the following
formula:
V
O1
= (R
1
+ R
2
)/R
1
x V
FB1
The negative output voltage range is - 8.0 V minimum up to a maximum of - 2.0 V. It is obtained connecting FB2 to V
REF
through R
3
and FB2 to PGND through R
4
). The value of negative output can be calculated using the
following formula:
V
O2
= (R
4
/R
3
) x V
REF
The device includes an undervoltage lockout circuit. When the STOD1412 is enabled (EN pin is pulled high), the device is turned OFF until the input voltage reaches the 2.55 V threshold. The UVLO circuit has a hysteresis of 50 mV, so once the device is on, it continues working until V
CC
falls below 2.50 V.
5.3 Enable
This function allows the switching ON and OFF of the device using a logic level signal. If the
EN pin is pulled high the device turns ON, given that the input voltage is higher than the undervoltage lockout threshold. Pulling the EN pin low turns OFF the device regardless of the UVLO state. In this condition the current consumption is reduced to lower than 1 µA.
When the device is turned OFF, there is no path for the current to flow from the input power supply to the load. In the device there are two switches that allow complete disconnection of the load. This function is useful to improve battery life when the device is not in operation.
5.5 Soft-start and inrush current
The device includes a soft-start feature to limit inrush current when the device is turned ON.
This function is added to minimize battery loading at startup.
Obsolete Product(s) - Obsolete Product(s)
The step-up and inverter converters include peak current limit circuitry. The inductor peak current cannot exceed 900 mA for the step-up stage and 1 A for the inverting stage.
Doc ID 13860 Rev 2 9/20
Introduction STOD1412
5.7.1 Inductor
The 1.3 MHz frequency allows the use of small inductors for both converters. In typical applications, a 4.7 µH and a 6.8 µH are recommended for step-up and inverting, respectively. Larger values of inductor reduce the ripple inductor current. The inductor current saturation rating must exceed the peak current.
5.7.2 Capacitors
In order to reduce the ripple voltage on the outputs it is recommended to use capacitors with low equivalent series resistance (ESR) on output filters. The interaction between the ESR value of the capacitor and peak inductor current determines the amplitude of the ripple on the output voltage. The suggested value for output capacitors is 4.7 µF.
In order to filter the input voltage variations, a ceramic capacitor must be connected between V
CC
and PGND. A minimum value of 2.2 µF is recommended. This value may be increased to further reduce the noise coming from input power supply. A 100 nF to
1 µF capacitor on the VREF pin is also recommended.
Board layout is important due to high current levels and high switching frequencies that could radiate noise. It is important to connect the signal GND pin, the input and output capacitor ground leads, and power ground to a single connection point to obtain a star ground configuration. This minimizes ground noise and improves regulation. It is useful to minimize lead lengths in order to reduce stray capacitance, trace resistance to avoid voltage drops and noise irradiation, especially to the feedback circuit, ground circuit and LX_ traces.
Place feedback resistors close to their respective feedback pins. Place input capacitors as close as possible to V
CC
and PGND.
Figure 4.
Star ground plane
Obsolete Product(s) - Obsolete Product(s)
10/20 Doc ID 13860 Rev 2
STOD1412
Figure 5.
Typical application circuit
Typical application
Table 6.
Symbol
External components (see
)
Parameter Min.
Typ.
Max.
Unit
Inductor 4.7
µH L
1
L
2
C
I
C
3
C
01,2
Inductor
Ceramic capacitor SMD
Ceramic capacitor SMD – OPTIONAL
Ceramic capacitor SMD
6.8
2.2
1
4.7
µH
µF
µF
µF
R3
Ceramic capacitor SMD
Feedback resistor
22
533 nF C
Fb
C
REF
1 µF Ceramic capacitor SMD
Obsolete Product(s) - Obsolete Product(s)
R1 Feedback resistors 470 k
Ω k
Ω
R2 Feedback resistors 166 k
Ω k
Ω
R4 Feedback resistor 100
Doc ID 13860 Rev 2 11/20
Typical performance characteristics
7 Typical performance characteristics
Figure 6.
System efficiency vs. output current
STOD1412
Figure 7.
I
PK
current step-up vs. input voltage
Figure 8.
I
PK
current inverting vs. input voltage
Figure 9.
Voltage reference vs. temperature
Figure 10.
V
FB1
on step-up vs. temperature Figure 11.
Line V
FB1
on step-up vs. temperature
Obsolete Product(s) - Obsolete Product(s)
12/20 Doc ID 13860 Rev 2
STOD1412 Typical performance characteristics
Figure 12.
V
FB2
on inverting vs. temperature Figure 13.
Line V
FB2
on inverting vs. temperature
Figure 14.
Load transient response (step-up) Figure 15.
Line transient response
V
IN
= 3.7 V, I
T = 25°C
OUT
= 3 mA to 30 mA, T
RISE
= T
FALL
= 30 µs,
Figure 16.
Startup voltage
V
IN
= 3 V to 3.5 V, I
OUT1,2
T = 25°C
= 120 mA, T
RISE
= T
FALL
= 50 µs,
Obsolete Product(s) - Obsolete Product(s)
V
IN
= 0 V to 2.5 V, T = 25°C
Doc ID 13860 Rev 2 13/20
Package mechanical data
8 Package mechanical data
STOD1412
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.
Obsolete Product(s) - Obsolete Product(s)
14/20 Doc ID 13860 Rev 2
STOD1412
Figure 17.
QFN16L package outline
Package mechanical data
Obsolete Product(s) - Obsolete Product(s)
7997239/A
Doc ID 13860 Rev 2 15/20
Package mechanical data
Table 7.
QFN16L mechanical data mm.
Dim.
Min.
Typ.
Max.
A
A1
A3 b
D
D2
E
E2
0.70
0
0.18
2.90
1.50
2.90
1.50
0.75
0.02
0.20
0.25
3
1.70
3
1.70
0.80
0.05
0.30
3.10
1.80
3.10
1.80
L e
(1)
0.30
0.50
0.40
1.
The value of “L” by JEDEC norm is min 0.35 - max 0.45.
0.50
STOD1412
Min.
0.028
0
0.007
0.114
0.059
0.114
0.059
0.012
inch.
Typ.
0.030
0.001
0.008
0.010
0.118
0.067
0.118
0.067
0.020
0.016
Max.
0.031
0.002
0.012
0.122
0.071
0.122
0.071
0.020
Obsolete Product(s) - Obsolete Product(s)
16/20 Doc ID 13860 Rev 2
STOD1412 Package mechanical data
Dim.
Ko
Po
P
T
Ao
Bo
D
N
A
C
Tape & reel QFNxx/DFNxx (3x3) mechanical data
Min.
mm.
Typ.
Min.
Max.
180
13.2
inch.
Typ.
12.8
20.2
60
0.504
0.795
2.362
14.4
3.3
3.3
1.1
4
8
0.130
0.130
0.043
0.157
0.315
Max.
7.087
0.519
0.567
Obsolete Product(s) - Obsolete Product(s)
Doc ID 13860 Rev 2 17/20
Package mechanical data
Figure 18.
QFN16L footprint - recommended data
STOD1412
Obsolete Product(s) - Obsolete Product(s)
18/20 Doc ID 13860 Rev 2
STOD1412
9 Revision history
Table 8.
Date
Document revision history
Revision
31-Aug-2007
16-Mar-2010
1
2
Initial release.
Changes
Revision history
Obsolete Product(s) - Obsolete Product(s)
Doc ID 13860 Rev 2 19/20
STOD1412
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20/20 Doc ID 13860 Rev 2
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