TI TPS62020DGQ

TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
600 mA/1.25 MHz HIGH-EFFICIENCY STEP-DOWN CONVERTER
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
DESCRIPTION
Up to 95% Conversion Efficiency
Typical Quiescent Current: 18 µA
Load Current: 600 mA
Operating Input Voltage Range: 2.5 V to 6.0 V
Switching Frequency: 1.25 MHz
Adjustable and Fixed Output Voltage
Power Save Mode Operation at Light load
Currents
Active-Low MODE pin on TPS62021
100% Duty Cycle for Lowest Dropout
Internal Softstart
Dynamic Output Voltage Positioning
Thermal Shutdown
Short-Circuit Protection
10 Pin MSOP PowerPad™ Package
10 Pin QFN 3 X 3 mm Package
The TPS6202x is a high efficiency synchronous
step-down dc-dc converter optimized for battery powered portable applications. This device is ideal for
portable applications powered by a single Li-Ion
battery cell or by 3-cell NiMH/NiCd batteries. With an
output voltage range from 6.0 V down to 0.7 V, the
device supports low voltage DSPs and processors in
PDAs, pocket PCs, as well as notebooks and
subnotebook computers. The TPS6202x operates at
a fixed switching frequency of 1.25 MHz and enters
the power save mode operation at light load currents
to maintain high efficiency over the entire load current
range. For low noise applications, the device can be
forced into fixed frequency PWM mode by pulling the
MODE pin high. The difference between the
TPS6202x and the TPS62021 is the logic level of the
MODE pin. The TPS62021 has an active-low MODE
pin. The TPS6202x supports up to 600-mA load
current.
APPLICATIONS
•
•
•
•
•
•
PDA, Pocket PC and Smart Phones
USB Powered Modems
CPUs and DSPs
PC Cards and Notebooks
xDSL Applications
Standard 5-V to 3.3-V Conversion
Typical Application Circuit (600-mA Output Current)
EFFICIENCY
vs
LOAD CURRENT
C3
10 µF
TPS62020
2
SW
VIN
3
SW
VIN
1 EN
FB
6
MODE PGND
4
GND
PGND
8
7
L1
10 µH
5
10
9
VO
0.7 V to VI / 600 mA
100
VO = 1.8 V
95
VI = 2.7 V
90
R1
C1
R2
C2
C4
10 µF
85
Efficiency − %
VI
2.5 V to 6 V
VI = 3.6 V
80
VI = 5 V
75
70
Mode = Low
65
60
55
VI = 3.6 V
Mode = High
50
45
40
0
0.01
0.10
1
10
100
1000
IL − Load Current − mA
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PowerPad is a trademark of Texas Instruments.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2003–2004, Texas Instruments Incorporated
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
These devices have limited built-in ESD protection. The leads should be shorted together or the device
placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
ORDERING INFORMATION
TA
PACKAGE MARKING
OUTPUT
VOLTAGE
MSOP (1)
QFN (2)
MSOP
QFN
MODE
Adjustable
TPS62020DGQ
TPS62020DRC
BBK
BBJ
MODE
Adjustable
TPS62021DGQ
TPS62021DRC
ASH
ASJ
MODE
3.3 V
TPS62026DGQ
TPS62026DRC
BKI
BKJ
–40°C to 85°C
(1)
(2)
PACKAGE
MODE PIN
LOGIC LEVEL
The DGQ package is available in tape and reel. Add R suffix (DGQR) to order quantities of 2500 parts per reel.
The DRC package is available in tape and reel. Add R suffix (DRCR) to order quantities of 3000 parts per reel.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range unless otherwise noted (1)
UNITS
Supply voltage
VIN (2)
–0.3 V to 7 V
Voltages on EN, MODE, FB, SW (2)
–0.3 V to VCC +0.3 V
Continuous power dissipation
See Dissipation Rating Table
Operating junction temperature range
–40°C to 150°C
Storage temperature range
–65°C to 150°C
Lead temperature (soldering, 10 sec)
(1)
(2)
260°C
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating
conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltage values are with respect to network ground terminal.
PACKAGE DISSIPATION RATINGS
(1)
PACKAGE
RθJA (1)
TA ≤ 25°C
POWER RATING
TA = 70°C
POWER RATING
TA = 85°C
POWER RATING
MSOP
60°C/W
1.67 W
917 mW
667 mW
QFN
48.7°C/W
2.05 W
1.13 W
821 mW
The thermal resistance, RθJA is based on a soldered PowerPAD using thermal vias.
RECOMMENDED OPERATING CONDITIONS
MIN
TYP
MAX
UNIT
VI
Supply voltage
2.5
6.0
VO
Output voltage range for adjustable output voltage version
0.7
VI
IO
Output current
L
Inductor (1)
10
µH
CI
Input capacitor (1)
10
µF
CO
Output capacitor (1)
10
µF
TA
Operating ambient temperature
–40
85
°C
TJ
Operating junction temperature
–40
125
°C
(1)
2
Refer to application section for further information
600
3.3
V
V
mA
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
ELECTRICAL CHARACTERISTICS
VI = 3.6 V, VO = 1.8 V, IO = 600 mA, EN = VIN, TA = –40°C to 85°C, typical values are at TA = 25°C (unless otherwise noted) (1)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
SUPPLY CURRENT
VI
Input voltage range
2.5
I(Q)
Operating quiescent current
IO = 0 mA, device is not switching
ISD
Shutdown supply current
EN = GND
VUVLO
Under-voltage lockout threshold
6.0
V
18
35
µA
0.1
1
µA
2.3
V
1.5
ENABLE AND MODE
VEN
EN high level input voltage
VEN
EN low level input voltage
1.4
IEN
EN input bias current
V(MODE)
MODE high level input voltage
V(MODE)
MODE low level input voltage
I(MODE)
MODE input bias current
EN = GND or VIN
V
0.01
0.4
V
1.0
µA
1.4
MODE = GND or VIN
V
0.01
0.4
V
1.0
µA
POWER SWITCH
P-channel MOSFET on-resistance
VI = VGS = 3.6 V
115
210
mΩ
P-channel MOSFET on-resistance
VI = VGS = 2.5 V
145
270
mΩ
P-channel leakage current
VDS = 6.0 V
1
µA
N-channel MOSFET on-resistance
VI = VGS = 3.6 V
85
200
mΩ
N-channel MOSFET on-resistance
VI = VGS = 2.5 V
115
280
mΩ
IIkg(N)
N-channel leakage current
VDS = 6.0 V
1
µA
IL
P-channel current limit
2.5 V < VI < 6.0 V
rDS(ON)
Ilkg(P)
rDS(ON)
0.9
Thermal shutdown
1.1
1.3
A
°C
150
OSCILLATOR
fS
VFB= 0.5 V
Oscillator frequency
1
VFB = 0 V
1.25
1.5
625
MHz
kHz
OUTPUT
VO
Adjustable output
voltage range
Vref
Reference voltage
TPS62020,
TPS62021
VFB
Feedback voltage
VO
Fixed output voltage
TPS62026 3.3 V
f
(1)
VIN
0.5
TPS62020,
TPS62021
Adjustable
IIkg(SW)
0.7
VI = 2.5 V to 6.0 V; IO = 0 mA
VI = 2.5 V to 6.0 V; 0 mA ≤ IO ≤ 600 mA
VI = 3.6 V to 6.0 V; IO = 0 mA
VI = 3.6 V to 6.0 V; 0 mA ≤ IO ≤ 600 mA
V
V
0%
3%
–3%
3%
0%
3%
–3%
3%
V
V
Line regulation (1)
VI = VO + 0.5 V (min 2.5 V) to 6.0 V, IO = 10
mA
0
%/V
Load regulation (1)
IO = 10 mA to 600 mA
0
%/mA
Leakage current into SW pin
VI > VO, 0 V≤ VSW ≤ VI
0.1
1
Reverse leakage current into pin SW
VI = open; EN = GND; VSW = 6.0 V
0.1
1
Short circuit switching frequency
VFB = 0 V
625
µA
µA
kHz
The line and load regulations are digitally controlled to assure an output voltage accuracy of ±3%.
3
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
PIN ASSIGNMENTS
DGQ PACKAGE
(TOP VIEW)
EN
VIN
VIN
GND
FB
NOTE:
1
10
2
9
3
8
4
7
5
6
DRC PACKAGE
(TOP VIEW)
PGND
PGND
SW
SW
MODE
EN
VIN
VIN
GND
FB
1
10
2
9
3
8
4
7
5
6
PGND
PGND
SW
SW
MODE
The PowerPAD must be connected to GND.
Terminal Functions
TERMINAL
NAME
NO.
I/O
DESCRIPTION
EN
1
I
Enable. Pulling EN to ground forces the device into shutdown mode. Pulling EN to VI enables the device. EN
should not be left floating and must be terminated.
VIN
2, 3
I
Supply voltage input
GND
4
FB
5
I
Feedback. Connect an external resistor divider to this pin.
If a fixed-output-voltage device is ued, connect FB directly to the output.
MODE
MODE
6
I
The difference between TPS6202x and TPS62021 is the logic level of the MODE pin. The TPS62021 has an
active-low MODE pin. The TPS6202x is forced into fixed-frequency PWM mode by pulling the MODE pin high.
Pulling the MODE pin low enables the Power Save Mode, operating in PFM mode (Pulse frequency modulation)
at light load current, and in fixed frequency PWM at medimum to heavy load currents. In contrast, the TPS62021
is forced into PWM mode by pulling the MODE pin low.
SW
7, 8
PGND
9, 10
4
Analog ground
I/O This is the switch pin of the converter and connected to the drain of the internal power MOSFETs
Power ground
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
FUNCTIONAL BLOCK DIAGRAM
VIN
Current limit Comparator
Undervoltage
Lockout
Bias supply
+
−
Soft
Start
EN
+
Ref
SkipComparator
−
V
Vcomp
Comparator
+
Saw Tooth
Generator
Ref
MODE
1.25 MHz
Oscillator
I
P−Channel
Power MOSFET
VIN
S
R
Control Logic
−
SW
Driver
Shoot−thru
Logic
SW
Comp High
N−Channel
Power MOSFET
Comp Low
Comp Low 2
Comp High
LoadComparator
−
Gm
R1
Compensation
+
R2
+
Comp Low
Comp Low 2
Vref = 0.5 V
MODE
(See Note A)
GND
−
+
−
FB
PGND
PGND
For the Adjustable Version the FB Pin Is
Directly Connected to the Gm Amplifier
NOTE A: The TPS6202x has an active-high MODE pin. The TPS62021 has an active-low MODE pin.
NOTE B: The resistor network R1 and R2 is only integrated in fixed-output devices.
5
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
η
Efficiency
vs Load current
η
Efficiency
vs Input voltage
4
IQ
No load quiescent current
vs Input voltage
5, 6
fs
Switching frequency
vs Input voltage
7
rDS(on)
P-Channel switch rDS(on)
vs Input voltage
8
rDS(on)
N-Channel rectifier switch rDS(on)
vs Input voltage
1, 2, 3
9
Load transient response
10
PWM operation
11
Power save mode operation
12
Start-up
13
EFFICIENCY
vs
LOAD CURRENT
100
EFFICIENCY
vs
LOAD CURRENT
100
VO = 3.3 V
95
90
VI = 3.6 V
Mode = Low
80
85
75
VI = 3.6 V
80
VI = 5 V
Mode = Low
Efficiency − %
Efficiency − %
VI = 2.7 V
90
85
70
65
75
VI = 5 V
Mode = Low
70
65
60
60
55
55
50
50
45
45
40
VI = 3.6 V
Mode = High
40
0
0.01
0.10
1
10
IL − Load Current − mA
Figure 1.
6
VO = 1.8 V
95
100
1000
0
0.01
0.10
1
10
IL − Load Current − mA
Figure 2.
100
1000
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
EFFICIENCY
vs
LOAD CURRENT
100
100
VO = 1.5 V
95
90
VO = 1.8 V
Mode = Low
95
VI = 2.7 V
85
VI = 3.6 V
75
IL = 250 mA
90
Efficiency − %
80
Efficiency − %
EFFICIENCY
vs
INPUT VOLTAGE
VI = 5 V
70
65
Mode = Low
60
IL = 500 mA
85
IL = 1 mA
80
55
50
75
Mode = High
45
40
0
0.01
0.10
1
10
IL − Load Current − mA
100
70
2.5
1000
4
4.5
5
Figure 3.
Figure 4.
QUIESCENT CURRENT
vs
INPUT VOLTAGE
QUIESCENT CURRENT
vs
INPUT VOLTAGE
5.5
6
5.5
6
7.5
MODE = High
MODE = Low
7
19
Quisecent Current − mA
TA = 85°C
21
Quisecent Current − µ A
3.5
VI − Input Voltage − V
23
TA = 25°C
17
TA = −40°C
15
13
11
6.5
5.5
5
4.5
4
7
3.5
2.8
3.2
3.6
4
4.4 4.8 5.2
VI − Input Voltage − V
Figure 5.
5.6
6
TA = 25°C
6
9
5
2.4
3
3
2.5
3
3.5
4
4.5
5
VI − Input Voltage − V
Figure 6.
7
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
SWITCHING FREQUENCY
vs
INPUT VOLTAGE
P-CHANNEL rDS(on)
vs
INPUT VOLTAGE
0.180
1.23
0.170
TA = 85°C
1.22
P−Channel r DS(on) − Ω
f − Switching Frequency − MHz
1.23
TA = 25°C
1.22
1.21
1.21
TA = −40°C
1.20
1.20
TA = 85°C
0.150
0.140
TA = 25°C
0.130
0.120
0.110
1.19
0.100
1.19
TA = −40°C
0.090
1.18
1.18
2.5
0.160
2.9
3.3
3.7 4.1 4.5
4.9
VI − Input Voltage − V
5.3
5.7
0.080
2.5
6
2.9
3.3
3.7 4.1 4.5
4.9
VI − Input Voltage − V
Figure 7.
Figure 8.
N-CHANNEL RECTIFIER rDS(on)
vs
INPUT VOLTAGE
LOAD TRANSIENT RESPONSE
0.150
VO
100 mV/div
0.130
TA = 85°C
0.120
TA = 25°C
0.110
0.080
0.070
TA = −40°C
0.050
2.5
2.9
3.3
3.7 4.1 4.5
4.9
VI − Input Voltage − V
Figure 9.
5.3
5.7
6
50 mA to 600 mA
0.090
0.060
8
VI = 3.6 V,
VO = 1.8 V,
PWM/PFM Operation
0.100
IO
N-Channel Rectifier r DS(on) − Ω
0.140
50 µs/div
Figure 10.
5.3
5.7
6
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
PWM OPERATION
POWER SAVE MODE OPERATION
IL
500 mA/div
VI = 3.6 V,
VO = 1.8 V
2.5 µs/div
500 ns/div
Figure 11.
Figure 12.
2 V/div
VI = 3.6 V,
VO = 1.8 V,
IO = 545 mA
VO
1 V/div
Enable
START-UP
II
200 mV/div
IL
500 mA/div
VO
20 mV/div
VO
20 mV/div
VSW
5 V/div
VSW
2 V/div
VI = 3.6 V,
VO = 1.8 V
200 µs/div
Figure 13.
9
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
DETAILED DESCRIPTION
OPERATION
The TPS6202x is a synchronous step-down converter that typically operates at a 1.25-MHz fixed frequency. At
moderate to heavy load currents the device operates in pulse-width modulation (PWM), and at light load currents
the device enters power-save mode operation using pulse-requency modulation (PFM). When operating in PWM
mode, the typical switching frequency is 1.25 MHz with a minimum switching frequency of 1 MHz. This makes
the device suitable for xDSL applications, minimizing RF (radio frequency) interference.
During PWM operation the converter uses a unique fast response voltage mode controller scheme with input
voltage feed-forward to achieve good line and load regulation allowing the use of small ceramic input and output
capacitors. At the beginning of each clock cycle initiated by the clock signal (S) the P-channel MOSFET switch
turns on and the inductor current ramps up until the comparator trips and the control logic turns off the switch.
The current limit comparator also turns off the switch in case the current limit of the P-channel switch is
exceeded. After the dead time preventing current shoot through, the N-channel MOSFET rectifier is turned on
and the inductor current ramps down. The next cycle is initiated by the clock signal, again turning off the
N-channel rectifier and turning on the P-channel switch.
The Gm amplifier as well as the input voltage determines the rise time of the saw tooth generator, and therefore,
any change in input voltage or output voltage directly controls the duty cycle of the converter, giving a very good
line and load transient regulation.
POWER SAVE MODE OPERATION
As the load current decreases, the converter enters power save mode operation. During power save mode the
converter operates with reduced switching frequency in PFM mode and with a minimum quiescent current
maintaining high efficiency.
The converter monitors the average inductor current and the device enters power save mode when the average
inductor current is below the threshold. The transition point between PWM and power save mode is given by the
transition current with the following equation:
V
I
I
transition
18.66 (1)
During power save mode the output voltage is monitored with the comparator by the threshold's comp low and
comp high. As the output voltage falls below the comp low threshold set to typically 0.8% above the nominal
output voltage, the P-channel switch turns on. The P-channel switch remains on until the transition current
Equation 1 is reached. Then the N-channel switch turns on completing the first cycle. The converter continues to
switch with its normal duty cycle determined by the input and output voltage but with half the nominal switching
frequency of 625-kHz typ. Thus the output voltage rises and, as soon as the output voltage reaches the comp
high threshold of 1.6%, the converter stops switching. Depending on the load current, the converter switches for
a longer or shorter period of time in order to deliver the energy to the output. If the load current increases and the
output voltage can not be maintained with the transition current Equation 1, the converter enters PWM again.
See Figure 11 and Figure 12 under the typical graphs section and Figure 14 for power save mode operation.
Among other techniques this advanced power save mode method allows high efficiency over the entire load
current range and a small output ripple of typically 1% of the nominal output voltage.
Setting the power save mode thresholds to typically 0.8% and 1.6% above the nominal output voltage at light
load current results in a dynamic voltage positioning achieving lower absolute voltage drops during heavy load
transient changes. This allows the converter to operate with small output capacitors like 10 µF or 22 µF and still
having a low absolute voltage drop during heavy load transient. Refer to Figure 14 as well for detailed operation
of the power save mode.
10
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
DETAILED DESCRIPTION (continued)
PFM Mode at Light Load
1.6%
Comp High
0.8%
Comp Low
VO
Comp Low 2
PWM Mode at Medium to Full Load
Figure 14. Power Save Mode Thresholds and Dynamic Voltage Positioning
The converter enters the fixed frequency PWM mode as soon as the output voltage falls below the comp low 2
threshold.
DYNAMIC VOLTAGE POSITIONING
As described in the power save mode operation sections before and as detailed in Figure 14 the output voltage
is typically 0.8% (i.e., 1% on average) above the nominal output voltage at light load currents, as the device is in
power save mode. This gives additional headroom for the voltage drop during a load transient from light load to
full load. In the other direction during a load transient from full load to light load the voltage overshoot is also
minimized by turning on the N-Channel rectifier switch to pull the output voltage actively down.
MODE (AUTOMATIC PWM/PFM OPERATION AND FORCED PWM OPERATION)
Connecting the MODE pin of the TPS6202x to GND enables the automatic PWM and power save mode
operation. The converter operates in fixed frequency PWM mode at moderate to heavy loads and in the PFM
mode during light loads, maintaining high efficiency over a wide load current range.
Pulling the TPS6202x MODE pin high forces the converter to operate constantly in the PWM mode even at light
load currents. The advantage is the converter operates with a fixed switching frequency that allows simple
filtering of the switching frequency for noise sensitive applications. In this mode, the efficiency is lower compared
to the power save mode during light loads (see Figure 1 to Figure 3). For additional flexibility it is possible to
switch from power save mode to forced PWM mode during operation. This allows efficient power management
by adjusting the operation of the TPS6202x to the specific system requirements.
The difference between the TPS6202x and the TPS62021 is the logic level of the MODE pin. The TPS62021 has
an active-low MODE pin. Pulling the TPS62021 MODE pin high enables the automatic PWM and Power Save
Mode.
100% DUTY CYCLE LOW DROPOUT OPERATION
The TPS6202x offers a low input to output voltage difference while still maintaining regulation with the use of the
100% duty cycle mode. In this mode, the P-Channel switch is constantly turned on. This is particularly useful in
battery powered applications to achieve longest operation time by taking full advantage of the whole battery
voltage range. i.e. The minimum input voltage to maintain regulation depends on the load current and output
voltage and can be calculated as:
V min V max I max r
max R
I
O
O
DS(on)
L
(2)
with:
•
•
IO(max) = maximum output current plus inductor ripple current
rDS(on)max = maximum P-channel switch tDS(on).
11
TPS62020
TPS62021
TPS62026
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
www.ti.com
DETAILED DESCRIPTION (continued)
•
•
RL = DC resistance of the inductor
VOmax = nominal output voltage plus maximum output voltage tolerance
SOFTSTART
The TPS6202x series has an internal softstart circuit that limits the inrush current during start-up. This prevents
possible voltage drops of the input voltage in case a battery or a high impedance power source is connected to
the input of the TPS6202x.
The softstart is implemented with a digital circuit increasing the switch current in steps of typically ILIM/8, ILIM/4,
ILIM/2 and then the typical switch current limit of 1.1 A as specified in the electrical parameter table. The start-up
time mainly depends on the output capacitor and load current, see Figure 13.
SHORT-CIRCUIT PROTECTION
As soon as the output voltage falls below 50% of the nominal output voltage, the converter switching frequency
as well as the current limit is reduced to 50% of the nominal value. Since the short-circuit protection is enabled
during start up the device does not deliver more than half of its nominal current limit until the output voltage
exceeds 50% of the nominal output voltage. This needs to be considered in case a load acting as a current sink
is connected to the output of the converter.
THERMAL SHUTDOWN
As soon as the junction temperature of typically 150°C is exceeded the device goes into thermal shutdown. In
this mode, the P-Channel switch and N-Channel rectifier are turned off. The device continues its operation when
the junction temperature falls below typically 150°C again.
ENABLE
Pulling the EN low forces the part into shutdown mode, with a shutdown current of typically 0.1 µA. In this mode,
the P-Channel switch and N-Channel rectifier are turned off and the whole device is in shut down. If an output
voltage is present during shut down, which could be an external voltage source or super cap, the reverse
leakage current is specified under electrical parameter table. For proper operation the enable (EN) pin must be
terminated and should not be left floating.
Pulling EN high starts up the device with the softstart as described under the section Softstart.
UNDERVOLTAGE LOCKOUT
The undervoltage lockout circuit prevents device misoperation at low input voltages. It prevents the converter
from turning on the switch or rectifier MOSFET with undefined conditions.
12
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
APPLICATION INFORMATION
ADJUSTABLE OUTPUT VOLTAGE VERSION
When the adjustable output voltage version TPS6202x is used, the output voltage is set by the external resistor
divider. See Figure 15.
The output voltage is calculated as:
V 0.5 V 1 R1
O
R2
(3)
with R1 + R2 ≤ 1 MΩ and internal reference voltage Vref typical = 0.5 V
R1 + R2 should not be greater than 1 MΩ because of stability reasons. To keep the operating quiescent current
to a minimum, the feedback resistor divider should have high impedance with R1+R2≤1 MΩ. Due to this and the
low reference voltage of Vref = 0.5 V, the noise on the feedback pin (FB) needs to be minimized. Using a
capacitive divider C1 and C2 across the feedback resistors minimizes the noise at the feedback, without
degrading the line or load transient performance.
C1 and C2 should be selected as:
1
C1 2 10 kHz R1
(4)
with:
•
•
R1 = upper resistor of voltage divider
C1 = upper capacitor of voltage divider
For C1 a value should be chosen that comes closest to the calculated result.
C2 R1 C1
R2
(5)
with:
•
•
R2 = lower resistor of voltage divider
C2 = lower capacitor of voltage divider
For C2, the selected capacitor value should always be selected larger than the calculated result. For example, in
Figure 15 for C2 100 pF are selected for a calculated result of C2 = 88.42 pF.
If quiescent current is not a key design parameter C1 and C2 can be omitted, and a low impedance feedback
divider has to be used with R1 + R2 < 100 kΩ. This reduces the noise available on the feedback pin (FB) as well
but increases the overall quiescent current during operation. The higher the programmed output voltage the
lower the feedback impedance has to be for best operation when not using C1 and C2.
VI
2.5 V to 6 V
C3
22 µF
TPS62020
2
VIN
3
VIN
1
EN
6
MODE
4
GND
8
SW
7
SW
FB 5
PGND 10
9
PGND
VO
1.8 V / 600 mA
L1
6.2 µH
R1
470 kΩ
R2
180 kΩ
C1
33 pF
C4
22 µF
C2
100 pF
Figure 15. Adjustable Output Voltage Version
Inductor Selection
The TPS6202x uses typically a 10-µH output inductor. Larger or smaller inductor values can be used to optimize
the performance of the device for specific operation conditions. When changing inductor values, the product of
the inductor value times output-capacitor value (L×C) should stay constant. For example, when reducing the
13
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
APPLICATION INFORMATION (continued)
inductor value, increase the output capacitor accordingly. See the application circuits in Figure 17, Figure 18, and
Figure 19. The selected inductor has to be rated for its dc resistance and saturation current. The dc resistance of
the inductance directly influences the efficiency of the converter. Therefore an inductor with the lowest dc
resistance should be selected for highest efficiency. Formula Equation 7 calculates the maximum inductor current
under static load conditions. The saturation current of the inductor should be rated higher than the maximum
inductor current as calculated with formula Equation 7. This is needed because during heavy load transient the
inductor current rises above the value calculated under Equation 7.
V
1– O
V
I
I V L
O
Lƒ
(6)
I
I max I max L
L
O
2
(7)
with:
•
•
•
•
7 = Switching frequency (1.25 MHz typical)
L = Inductor value
∆IL= Peak-to-peak inductor ripple current
ILmax = Maximum inductor current
The highest inductor current occurs at maximum VI.
Open core inductors have a soft saturation characteristic and they can usually handle higher inductor currents
versus a comparable shielded inductor. A more conservative approach is to select the inductor current rating for
the maximum switch current of 1.3 A for the TPS6202x. Keep in mind that core material differs from inductor to
inductor, and this impacts efficiency, especially at high switching frequencies. Refer to Table 1 and the typical
applications and inductors selection.
Table 1. Inductor Selection
INDUCTOR VALUE
DIMENSIONS
COMPONENT SUPPLIER
10 µH
6,6 mm × 4,75 mm × 2,92 mm
Coilcraft DO1608C-103
10 µH
5,0 mm × 5,0 mm × 3,0 mm
Sumida CDRH4D28-100
3.3 µH
5,0 mm × 5,0 mm × 2,4 mm
Sumida CDRH4D22 3R3
6.8 µH
5,8 mm × 7,4 mm × 1,5 mm
Sumida CMD5D13 6R8
Output Capacitor Selection
The advanced, fast-response voltage-mode control scheme of the TPS6202x allows the use of small ceramic
capacitors with a typical value of 10 µF and 22 µF without having large output voltage under and overshoots
during heavy load transients. Ceramic capacitors having low ESR values have the lowest output voltage ripple
and are recommended. If required, tantalum capacitors may be used as well. Refer to Table 2 for component
selection. If ceramic output capacitors are used, the capacitor RMS ripple current rating always meets the
application requirements. Just for completeness the RMS ripple current is calculated as:
V
1– O
V
I
I
V 1
RMSCout
O
Lƒ
2 3
(8)
At nominal load current the device operates in PWM mode and the overall output voltage ripple is the sum of the
voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charging and discharging the
output capacitor:
14
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
V
1– O
V
I
V V O
O
Lƒ
1
ESR
8C ƒ
O
(9)
Where the highest output voltage ripple occurs at the highest input voltage, VI.
At light load currents, the device operates in power save mode and the output voltage ripple is independent of
the output capacitor value. The output voltage ripple is set by the internal comparator thresholds. The typical
output voltage ripple is 1% of the nominal output voltage.
Input Capacitor Selection
Because of the nature of the buck converter having a pulsating input current, a low ESR input capacitor is
required for best input voltage filtering and minimizing the interference with other circuits caused by high input
voltage spikes. The input capacitor should have a minimum value of 10 µF for the TPS6202x. The input capacitor
can be increased without any limit for better input voltage filtering.
Table 2. Input and Output Capacitor Selection
CAPACITOR
VALUE
CASE SIZE
10 µF
0805
Taiyo Yuden JMK212BJ106MG
TDK C12012X5ROJ106K
Ceramic
Ceramic
10 µF
1206
Taiyo Yuden JMK316BJ106KL
TDK C3216X5ROJ106M
Ceramic
22 µF
1206
Taiyo Yuden JMK316BJ226ML
Ceramic
22 µF
1210
Taiyo Yuden JMK325BJ226MM
Ceramic
COMPONENT SUPPLIER
COMMENTS
Layout Considerations
For all switching power supplies, the layout is an important step in the design especially at high peak currents
and switching frequencies. If the layout is not carefully done, the regulator might show stability problems as well
as EMI problems. Therefore, use wide and short traces for the main current paths as indicated in bold in
Figure 16. These traces should be routed first. The input capacitor should be placed as close as possible to the
IC pins as well as the inductor and output capacitor. The feedback resistor network should be routed away from
the inductor and switch node to minimize noise and magnetic interference. To further minimize noise from
coupling into the feedback network and feedback pin, the ground plane or ground traces should be used for
shielding. A common ground plane or a star ground as shown below should be used. This becomes very
important especially at high switching frequencies of 1.25 MHz.
The Switch Node Must Be
Kept as Small as Possible
TPS62020
VI
C3
22 µF
2
3
1
6
4
VIN
VIN
EN
MODE
GND
8
L1
6.2 µH
SW
7
SW
FB 5
10
PGND
9
PGND
VO
C2
22 µF
Figure 16. Layout Diagram
15
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
THERMAL INFORMATION
One of the most influential components on the thermal performance of a package is board design. In order to
take full advantage of the heat dissipating abilities of the PowerPAD™ packages, a board should be used that
acts similar to a heat sink and allows for the use of the exposed (and solderable), deep downset pad. For further
information please refer to Texas Instruments application note (SLMA002) PowerPAD Thermally Enhanced
Package.
The PowerPAD™ of the 10-pin MSOP package has an area of 1,52 mm × 1,79 mm (±0,05 mm) and must be
soldered to the PCB to lower the thermal resistance. Thermal vias to the next layer further reduce the thermal
resistance.
TYPICAL APPLICATIONS
Vin
3.6V to 6.0V
L1
3.3uH
TPS62020
2
3
1
6
4
C3
10uF
8
SW
SW 7
5
FB
PGND 10
VIN
VIN
EN
MODE
GND
PGND 9
Vout
3.3V/0.6A
C4
22uF
R1
620k
C1
22pF
R2
110k
C2
150pF
C5
22uF
Figure 17. Li-Ion to 3.3 V With Improved Load Transient Response
Vin
2.5V to 6.0V
TPS62020
C3
10uF
2
3
1
6
4
VIN
VIN
EN
MODE
GND
8
SW
SW 7
5
FB
PGND 10
PGND 9
L1
6.8uH
R1
620k
R2
240k
Vout
1.8V/0.6A
C1
22pF
C4
22uF
C2
68pF
Figure 18. 1.8 V Output Using 6.8 µH Inductor
Vin
2.5V to 6.0V
TPS62020
C3
10uF
2
3
1
6
4
VIN
VIN
EN
MODE
GND
8
SW
SW 7
5
FB
10
PGND
PGND 9
L1
10uH
R1
470k
R2
330k
Vout
1.2V/0.6A
C1
33pF
C2
68pF
Figure 19. 1.2 V Output Using 10 µH Inductor
16
C4
10uF
TPS62020
TPS62021
TPS62026
www.ti.com
SLVS076C – JUNE 2003 – REVISED DECEMBER 2004
Vin
3.6 V to 6 V
C1
10 F
TPS62026
2
3
1
6
4
VIN
VIN
EN
MODE
GND
8
L1
6.8 H
SW
7
SW
FB 5
PGND 10
9
PGND
Vout
3.3 V/0.6 A
C2
22 F
Figure 20. TPS62026 Fixed 3.3 V Output Using 6.8 µH inductor
Vin
3.6 V to 6 V
C1
10 F
TPS62026
2
VIN
3
VIN
1
EN
6
MODE
4
GND
SW
SW
FB
PGND
PGND
8
7
5
10
9
L1
10 H
Vout
3.3 V / 0.6 A
C2
10 F
Figure 21. TPS62026 Fixed 3.3 V Output Using 10 µH inductor
17
PACKAGE OPTION ADDENDUM
www.ti.com
26-Jul-2005
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
TPS62020DGQ
ACTIVE
MSOPPower
PAD
DGQ
10
TPS62020DGQR
ACTIVE
MSOPPower
PAD
DGQ
TPS62020DGQRG4
ACTIVE
MSOPPower
PAD
TPS62020DRCR
ACTIVE
TPS62020DRCRG4
80
Lead/Ball Finish
MSL Peak Temp (3)
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
10
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
DGQ
10
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
SON
DRC
10
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
ACTIVE
SON
DRC
10
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
TPS62021DGQ
PREVIEW
MSOPPower
PAD
DGQ
10
TPS62021DGQR
ACTIVE
MSOPPower
PAD
DGQ
10
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPS62021DRCR
ACTIVE
SON
DRC
10
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
TPS62021DRCRG4
ACTIVE
SON
DRC
10
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
TPS62026DGQ
ACTIVE
MSOPPower
PAD
DGQ
10
80
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPS62026DGQG4
ACTIVE
MSOPPower
PAD
DGQ
10
80
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPS62026DGQR
ACTIVE
MSOPPower
PAD
DGQ
10
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPS62026DGQRG4
ACTIVE
MSOPPower
PAD
DGQ
10
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPS62026DRCR
ACTIVE
SON
DRC
10
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
TPS62026DRCRG4
ACTIVE
SON
DRC
10
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
80
TBD
Call TI
Call TI
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS) or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
26-Jul-2005
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 2
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
any product or service without notice. Customers should obtain the latest relevant information before placing
orders and should verify that such information is current and complete. All products are sold subject to TI’s terms
and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI
deems necessary to support this warranty. Except where mandated by government requirements, testing of all
parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for
their products and applications using TI components. To minimize the risks associated with customer products
and applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,
copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process
in which TI products or services are used. Information published by TI regarding third-party products or services
does not constitute a license from TI to use such products or services or a warranty or endorsement thereof.
Use of such information may require a license from a third party under the patents or other intellectual property
of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is without
alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction
of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for
such altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that
product or service voids all express and any implied warranties for the associated TI product or service and
is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Following are URLs where you can obtain information on other Texas Instruments products and application
solutions:
Products
Applications
Amplifiers
amplifier.ti.com
Audio
www.ti.com/audio
Data Converters
dataconverter.ti.com
Automotive
www.ti.com/automotive
DSP
dsp.ti.com
Broadband
www.ti.com/broadband
Interface
interface.ti.com
Digital Control
www.ti.com/digitalcontrol
Logic
logic.ti.com
Military
www.ti.com/military
Power Mgmt
power.ti.com
Optical Networking
www.ti.com/opticalnetwork
Microcontrollers
microcontroller.ti.com
Security
www.ti.com/security
Telephony
www.ti.com/telephony
Video & Imaging
www.ti.com/video
Wireless
www.ti.com/wireless
Mailing Address:
Texas Instruments
Post Office Box 655303 Dallas, Texas 75265
Copyright  2005, Texas Instruments Incorporated