Cookbook DC DC
Transcript of Cookbook DC DC
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DC/DC conversion Cookbook
A simple step by step guide to select the most appropriate
voltage regulator for your application
Piercarlo Scimonelli
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Presentation outline
• What you need to know, to discuss intelligently
• Checklist and Selection Procedure
• Examples / ST products
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Voltage Regulators
A Voltage Regulator keeps a constant Output Voltage with varying:
• Output current
load regulation
• Input voltage line regulation
Voltage
Regulator
Input VoltageOutput Voltage
(Iout)
The three most important parameters: Vin, Vout, Iout
(Vout)(Vin)
Output Current
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Ideal Voltage Regulator V-I Characteristic
Vout
Iout
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Voltage Regulator simplified block diagram
Voltage regulators operate by comparing the output voltage to an
internal fixed reference. The difference is amplified and used to control
the output voltage. This is what we call a closed-loop feedback.
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Classification of power switching topologies
Source: APPLICATION BRIEF 0014 (N.Siciliano)
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Step down Converter (Buck)
ISW1
ISW2
IL
Vsw
Io
Vo
TON
T
T D
V
V ON
IN
O
T
TON
SW2
SW1 IL
Io
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Closing the loop – Voltage Mode
VC
sawtooth
D·Ts
Ts
Closed Loop Feedback (Voltage Mode)
L597x
L598x
L798x
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RSEN
Vin
L
Co
R Vo
PWM
Comparator
Slope
vc
Vref
R1
R2
VFB
iL signal
Ki
Error
Op-Amp
Compensation
Network
Slope comp
Inductor
current signal
Error OpAmp output (Vc)
Closing the loop – Current Mode
Closed Loop Feedback (Current Mode)
D·Ts
Ts
ST1Sx
L692x
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Power dissipation in Voltage Regulators
1) Power dissipated when the switches are closed (conduction losses):
PON = IOUT2 x (RDSONHS x D + RDSONLS x (1-D) + RL)
2) Power dissipated during the commutations (switching losses):
PSW = VIN x IOUT x FSW x (TON + TOFF)/2
3) Power dissipated when the device is not switching:
PQ = VIN x IQ
Power dissipated in a linear regulator:
PD = (VIN-VOUT) x IOUT + VIN x IQ
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Example: low Iq regulators in powering STM32
Current consumption:• Depends on operating mode
• Decreases at lower VDD
• Inreases with temperature
• Increases with clock speed
Supply current in standby is the same order of magnitude as the quiescent current
of voltage regulators
STM32L Vcc: 1.8V to 3.6V, Icc: 1uA to 100mA
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Input Voltage from 1.5V to 5.5V Ultra Low Quiescent Current:
1.0 μA (typ) at no load 1 nA (typ) in OFF mode
Fixed VOUT: 0.8V to 3.3V Excellent load transient response Stable with low ESR, SMD ceramic caps
STLQ015150mA, Ultra Low Quiescent Current LDO regulator
SOT666-6L (1.2x1.6mm)
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Switching Frequency ImpactPerformance
• Efficiency (needs low frequency)
• Thermal (needs low frequency) • Output Voltage Ripple (needs h igh frequency)
• Dynamic Performance (need h igh frequency)
• Board space availability (needs h igh frequency)
Typical cases:
~100kHz
To maximize
efficiency (Energy
harvesting) SPV1040
250-500KHz
High voltage buckregulators(Industrial/Automotive)L7985, L7986,PM668x
600KHz-1MHzCost/performancetrade-off
(Consumer/Computer)ST1S40, L6738
1MHz-3MHzPortableapplications / sizeconstraints(Trade off betweenboard space and
efficiency)ST1S31/32,STBB1, STLA02
3MHz up to6MHzExtreme boardspaceconstraints(PortableFitness, Smartphones/tablets)
STBB2,ST1S15
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High efficiency at light load: L6925/6/8Step-down switching regulators
• VIN : 2V 5.5V (2.7V 5.5V for L6925)
• VOUT: adjustable 0.6V VIN (100% DC)•
1% output voltage accuracy
• IOUT up to 800mA• 25uA quiescent current• Selectable Low noise or low consumption mode (PWM/PFM)• Freq.: 600KHz, synchronizable up to 1.4 MHz (L6925/6)• Freq.: 1.4MHz synchronizable up to 2 MHz (L6928)
• Current Mode Control• Thermal shut down (150C)
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Differentiating functions:
L6925: LBI & LBO, UVLO @ 2.7VL6926/L6928: PGOOD & RUN
L6925
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L6928 low noise or low power (burst) mode
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Low noise
Forced PWM
Burst mode
High efficiency
Vin 4.2VVout 1.5V
Iout 30mA
Cin/Cout 10uF
Rc 20Kohm
Cc 330pF
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Switching regulator selection based on output current
Single Output Switching Controller: external mosfets, up to30A load, very high efficiency
Switching Converter: internal mosfet(s), up to 5A load, compact
Multiphase controllerLoad higher than 30AHigh efficiency, low ripple, fasttransient response, small i/o filters
Multi-Output Controller or ConverterCompactness
HS1
LS1
HS1
LS1
HS1LS1
HS2
LS2
HS1
LS1
HS2
LS2
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The drop-out voltage is the minimum voltage across the regulator to maintain regulation
LDO: Low Drop-Out (voltage regulator)
Vin
Vout
Vin - Vout
Vin
Vout
Vin - Vout
Vin
VoutVin - Vout
Standard Linear
Regulators
(L78xx, LM317)
Vdrop >2V
Semi Low-Drop
(LD1117/LD108x)
Vdrop 0.8V-1.5V
Very Low-Drop
(LFxx/LD29xxx) Vdrop 0.2V-0.7V
Ultra
LDO (LD39xxx)
Vdrop
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Load Transient Response
VIN=12V, VOUT=3.3V, SRILOAD=2.5A/us
IL
0.5A/div
VOUT AC coupled
100mV/div
COUT=47uF
L=6.8uH
FSW=500kHz
Timescale
100us/div
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STLQ015 Load Transient
Load Transient Response
VIN=5.5V CIN=1µF, COUT=10µF, IOUT= from 1µA to 10mA
Vout
Iout
Tradeoff between:
BW of Error Amplifiervs.
Power consumption
Static Load Regulation
{{Load Transient response
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Soft-Start
2
11
2048
6.0
R
RSRSR
F
SR
VREF VOUT
SW
VREF L598x• Staircase ramp on internal VREF• 64 steps, 9mV each step
• 32 clock cycles each step
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Synchronous rectification vs. non-synchronous
ST1S10
L7981
Is a synchr. converter
always more efficient
than a non-synchr?
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Application requirements in a DC/DC conversion - summary
• Input Voltage (VIN)
• Output Voltage (VOUT)
• Output DC current (IOUT)• Power Conversion Efficiency: a measure of power losses smaller package
and longer battery life
• Switching frequency: ON/OFF time of power switch Impacts size of external
components and efficiency
• Quiescent Current (Iq): required to power internal circuitry Impact on light
load efficiency• Package Thermal Resistance Rth: ability to dissipate heat impact on board
space and robust thermal design
• Switching control (PWM – PFM): noise vs. efficiency at light load
• Feedback loop (Voltage Mode vs. Current Mode)
• …
The best device
is that which fits
the application
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• From Vin and Vout, select the topology (step-up, step down, buck-boost)
• Based on the output current and efficiency, choose between controller (ext.
FETs), converter (int. FETs) or Linear
• Select the device starting from the input voltage spec and max DC current
(if integrated FETs) to meet the application requirements of input voltage
range and load
• Consider any other design constraint: operating temperature range,
switching frequency, quiescent current, light load efficiency,synchronization, board space, transient response, power good, soft start,
output ripple etc… etc…
• Always ask what is “key” to the application
DC/DC Selection Procedure Summary
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PMICs
ASSP
ASICs
Switching Converters (int. FET)
& LED drivers
Battery & Power Management
Switching Controllers (ext. FETs)
Single and Multi output
Single and Multi phase
Power over Ethernet (PoE)
DC-DC Conversion Portfolio27
Linear Voltage Regulators
Low Drop Out (LDOs)
Shunt Voltage Ref.
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Switching Converter segmentation28
Automotive Grade, high Vin
A597x, A798x
Consumer Value Line
12V Vin, 3-4A, synchr.
ST1S40, ST1S41
Synchronous, high at light load
PMxx, ST1Sxx, L692x
Battery powered applications
L692x, PM6644, ST1S1x
Non synchronous, high Vin
ST1S14, L798x, L597x, L598x
High performance, 3-5A synchr.
PM8903, ST1S31/2, L5988/89
Continuous output current from 350mA to 4A
Wide range of max input voltage: 5V TO 60V
SOT23, Q/DFN3x3 and 4x4mm, HSO8, and TSSOP
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Step Down Converters – First buying choice
0
10
20
30
40
50
60
0 1 2 3 4 5 6
MAXIMUM OUTPUT CURRENT
L5970
ST1S06
ST1S03
ST1S14
L7981
L6925/6/8
ST1S10
ST1S09ST1S12
ST2S06
L5986L5985/45
L5973/4A
L5983
L5972/3A
L5981L5980
Synchronuos
NON-Synchronous
ST2S08
L4976 L4971 L4978 L4973
L6902
ST1S30ST1S15
Synchr. high at light load
PM8903ST1S03A
PM6644
ST1S41L5987/47
ST1S40
L5988/89
L7986L7985
L7980
L5974/5A L5975
ST1S32ST1S31
PGood
M A X I M U
M O
P E R A T I N G I
N P U T V O L T A G E
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2-3A output current in QFN3x3-10L and HSOP8 packages
P-channel power MOS: 100% DC operation and no bootstrap capacitor
High switching frequency (250KHz, adjustable up to 1MHz) withSynchronization capability (180° out of phase)
Wide input voltage range (4.5V up to 38V)
200ns minimum Ton
Internal Soft-start
Enable pin
Embedded protection features Suitable for MLCC output filter
Typ RDSon=150mΩ
L7985-L7986
QFN 3x3 10L - Rth j-amb 60
C/W
HSO8 - Rth j-amb 40° C/W
L7986/A
L7985/A 2A / up to 1MHz
3A / up to 1MHzQFN10 3x3 HSOP8
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Switching Frequency: 800kHz
Continuous output Current Capability: 3/4A 4/5A peak current limit
Output Voltage: Adjustable from 0.8V
Operating Input voltage 4V to 18V
Ceramic Capacitors and small Inductor
Soft-Start integrated circuit
Integrated 69mOhm Low side R DSon Integrated 95mOhm High side R DSon
Efficiency: up to 95%
Enable pin or Power Good
SO8, HSOP8 and MLP4x4 packages
Pin-to-pin with ST1S10
ST1S40/41
ST1S41 4A / 850kHz
ST1S40 3A / 800kHzDFN – 8L4x4mm
SO-8
HSOP-8
Package OutputCurrent
Commercial Code
SO8 3A ST1S40IDR
SO8-BW 3A ST1S40IPHR
DFN4x4 – 8L 3A ST1S40IPUR
DFN4x4 – 8L 4A ST1S41PUR
HSOP8 4A ST1S41PHR
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PM6644350mA step down and 3.3V voltage reference
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4.5V to 25V input voltage range (35V AMR)
Vout: fixed 3.465V or adjustable 0.9V to 8V 350mA valley current limit
Constant On-Time Control
Progr. switching frequency in PWM mode
Pulse skipping mode at light load
Latched OVP and UVP
High accuracy (±0.6%) 3.3V reference
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LDO Positioning (≤500mA)
0
5
10
15
20
25
30
0 100 200 300 400 500 600 M A X I M U M O
P E R A T I N G I
N P U T V O L T A G E
P. Scimonelli - APM – Jun 2011
ST715
L4931
STLQ50
LD2980
LD39050
LDFMxx
LFxx
KFxx
Ultra-low drop VDROP
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LDO Positioning (≥500mA)
0
5
10
15
20
25
30
35
0 500 1000 1500 2000 2500 3000 3500
MINIMUM GUARANTEED OUTPUT CURRENT
P. Scimonelli - APM – Jun 2011
LD39050
AG
LD39080
LD29080
LD1117
LD39100
ST1L02
ST1L04
LD1117A
L4941
L4940
LD1086
ST1L05 LD49150
LD29150
LD39150
LD49300
LD39300
LD29300
LD1085
LDFMxx
LFxx
KFxxLDFMxx
Ultra-low drop VDROP
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LDOs in portable applications
• LD39015J: 150mA - CSP4 bumps 1x1mm2
• LD39115J: 150mA - CSP4 bumps 0.8x0.8mm2
• LD39030SJ : 300mA, Soft-Start - CSP4 bumps 0.8x0.8mm2
• LD59015: 150mA, Very High PSRR, SC70
• LDCL015: 150mA – Capless, SOT23
• LDLN015: 150mA – Very Low Noise, DFN2x2
• LD39130: 300mA - CSP4 bumps 0.69x0.69mm2 and DFN 1.2x1.3
DC/DC i f 5V Vi l
http://images.google.it/imgres?imgurl=http://erinni.files.wordpress.com/2008/06/apple_ipod_nano.jpg&imgrefurl=http://erinni.wordpress.com/2008/06/30/ipod/&usg=__RD5Nd8I_7OJnH512YXjFQWRyc38=&h=389&w=295&sz=11&hl=it&start=4&um=1&tbnid=zLQaciAPDhb53M:&tbnh=123&tbnw=93&prev=/images?q=ipod+nano&hl=it&um=1http://images.google.it/imgres?imgurl=http://axelll.files.wordpress.com/2009/07/apple-netbook-tablet.jpg&imgrefurl=http://axelll.wordpress.com/2009/07/19/macsipad-the-apple-netbook/&usg=__xHjW2at35br09GFp1LQTraQP22Y=&h=306&w=540&sz=44&hl=it&start=7&um=1&tbnid=SBbiZk653Dg58M:&tbnh=75&tbnw=132&prev=/images?q=apple+netbook&hl=it&um=1
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DC/DC conversion for 5V Vin or lowerVoltage Regulation & Battery Chargers
STBB1 Buck boostSTLQ015 1.7uA Iq, 150mA Iout, LDOSTLQ50 3 μA Iq, 50 mA Iout, LDO
LD39015/LD39115 Low noise, 150 mA Iout, on/offL6924D Lithium battery chargerSTW4102 – Lithium Battery chargerL6920D 1 A step-up, low Iq, down to 0.6 VinL6928 Sync step-down, 95 % 2-5.5 VinST1S15 - 500mA, 6MHz, high efficiency buckPM6644 - 350mA, high efficiency buck + 3.3V VrefSPV1040 boost with MPPT for solar battery chargersLMV4041- 1.2V Vref with 0.1% accuracy in SC70
Display drivers STLA02 (6 LED backlight driver)STLED25 (2x5 LED backlight driver)STP2/4CMP (2/4 ch charge pump)STODxx (AMOLED)
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DC/DC conversion for 12V Vin
Part Numb er V INPUT /V OUT range F SW features Package
L6726A, L6727Up to 19V VINPUT,
0.8V min VOUT 270/300khZ EN, SS, OCP, OVP, UVP SO8
L6728Up to 13,2V (15V ABS) VINPUT,
0.8V min VOUT300/600KHz EN, SS, OVP, OCP, PGOOD DFN10
L6725, L6730
L6731, L6732
4.5V to 14V VINPUT,
0.6V min VOUT Up to 1MHz
OVP(Latch - No Latch), UVP, OCP (CC or HICCUP),
PGOOD (with adj. delay) , SS (Sink - No Sink), IHN, Extor Internal REF, Adj UVLO, SYNC., Sink- No sink cap.
SO16N
HTSSOP16
QFN24 4x4
HTSSOP20
L6738Up to 19V VINPUT,
0.8V min VOUT Adj.
EN, SS, OVP, OCP, PGOOD, differential CS &
“GREEN low power mode” QFN16 3x3
• Consumer
• Computer
• Anything powered off your friendly wall wart
CONTROLLERS (Ext.FETs)
CONVERTERS (Int.FETs)
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DC/DC conversion for 24V to 55V Vin
PNVOUT #
(SW +LDO)
VOUTSW
1
VOUTSW
2
VOUTS
W 3VOUTLDO(S) ILDO VIN range package
PM6670/A 1+1 Adj. - - VINLDO /2 2A Up to 28V /36V QFN 4x4
PM6675/A 1+1 Adj. - - Adj. 2A Up to 28V/36V QFN 4x4
PM6680/A 2+1 Adj. Adj. - 5V 200mA Up to 28V/36V QFN 5x5
PM6681/86 2+1 Adj. Adj. - Adj. 100mA Up to 28V QFN 5x5
PM6685 2+2 3.3V 5V - (1)3.3V + (2)5V 100mA up to 28V QFN 5x5
• Industrial Applications
• Printers
• Automotive/Marine battery
Powered applications
CONTROLLERS (Ext.FETs)
CONVERTERS (Int.FETs)
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Tools and resources
D i S it
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eDesign Suite www.st.com/edesignstudio
40
Complete designs in a few steps starting from input voltage, output voltage and current
Interactive schematics and BOM: change the parameters of external components
Evaluate the performance of your design: stability, thermal, efficiency,…
Connect to Cadence® Orcad Pspice
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A complete design in a few steps…..
Login to
www.st.com/edesignstudio
(after online registration)
Input your specifications
The design is ready
Create a new project and
choose an application type
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Helps select the optimal IC for your needs
You can filter the IC selecting specific features
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Evaluate the performance of your design
Simulates key voltage and current waveforms, displays bode plots, power losses and efficiency
Loss distribution
Waveforms simulator Bode plots
Efficiency
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Your design gets portable and exportable
Save your project to ST server/eDesign Studio My Projects folder
It can accessed from ANY computer through your eDesign Studio account
Export the current design project for Pspice Simulat ion in OrCAD
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Print a summary of your project
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Parametric Search on www.st.com 46
25/04/2012Presentation Title
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