LTC3850EUF#PBF Linear Technology, LTC3850EUF#PBF Datasheet

IC CNTRLR STP DWN SYNC 28-QFN

LTC3850EUF#PBF

Manufacturer Part Number
LTC3850EUF#PBF
Description
IC CNTRLR STP DWN SYNC 28-QFN
Manufacturer
Linear Technology
Series
PolyPhase®r
Type
Step-Down (Buck)r
Datasheet

Specifications of LTC3850EUF#PBF

Internal Switch(s)
No
Synchronous Rectifier
Yes
Number Of Outputs
2
Voltage - Output
0.8 ~ 23.3 V
Current - Output
100mA
Frequency - Switching
250kHz ~ 780kHz
Voltage - Input
4 ~ 24 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
28-QFN
Primary Input Voltage
24V
No. Of Outputs
2
Output Current
100mA
No. Of Pins
28
Operating Temperature Range
-40°C To +85°C
Msl
MSL 1 - Unlimited
Supply Voltage Range
4V To 24V
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Power - Output
-

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
LTC3850EUF#PBFLTC3850EUF
Manufacturer:
LT
Quantity:
10 000
Company:
Part Number:
LTC3850EUF#PBFLTC3850EUF
Manufacturer:
LINEAR/凌特
Quantity:
20 000
Company:
Part Number:
LTC3850EUF#PBF
0
Company:
Part Number:
LTC3850EUF#PBFLTC3850EUF#TRPBF
Manufacturer:
LT/凌特
Quantity:
20 000
Company:
Part Number:
LTC3850EUF#PBFLTC3850EUF#TRPBF
Manufacturer:
LINEAR
Quantity:
19 017
FEATURES
APPLICATIONS
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
L, LT, LTC, LTM, OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners. Protected by U.S.
Patents, including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258.
TYPICAL APPLICATION
V
OUT1
3.3V
5A
Dual, 180° Phased Controllers Reduce Required
Input Capacitance and Power Supply Induced Noise
High Efficiency: Up to 95%
R
±1% 0.8V Output Voltage Accuracy
Phase-Lockable Fixed Frequency 250kHz to 780kHz
Supports Pre-Biased Output
Dual N-Channel MOSFET Synchronous Drive
Wide V
Operation
Adjustable Soft-Start Current Ramping or Tracking
Foldback Output Current Limiting
Output Overvoltage Protection
Power Good Output Voltage Monitor
28-Pin 4mm × 4mm, 4mm × 5mm QFN and Narrow
SSOP Packages
Notebook and Palmtop Computers
Portable Instruments
Battery-Operated Digital Devices
DC Power Distribution Systems
SENSE
2.2µH
100µF
6V
2.2k
IN
or DCR Current Sensing
63.4k
Range: 4V to 24V (30V for LTC3850I)
High Efficiency Dual 3.3V/2.5V Step-Down Converter
20k
0.1µF
0.1µF
15k
220pF
500kHz
0.1µF
TG1
BOOST1
SW1
BG1
MODE/PLLIN
I
SENSE1
RUN1
SENSE1
V
I
LIM
TH1
TK/SS1
FB1
V
IN
+
LTC3850
PGOOD INTV
SGND
FREQ/PLLFLTR
SENSE2
SENSE2
BOOST2
TK/SS2
PGND
RUN2
SW2
V
CC
BG2
I
TG2
TH2
FB2
+
0.1µF
10k
10nF
0.1µF
0.1µF
4.7µF
15k
220pF
DESCRIPTION
The LTC
step-down switching regulator controller that drives all
N-channel power MOSFET stages. A constant-frequency
current mode architecture allows a phase-lockable fre-
quency of up to 780kHz. Power loss and supply noise are
minimized by operating the two controller output stages
out of phase.
OPTI-LOOP
to be optimized over a wide range of output capacitance
and ESR values. The LTC3850 features a precision 0.8V
reference and a power good output indicator. A wide 4V to
24V (28V maximum/30V for LTC3850I) input supply range
encompasses most battery chemistries and intermediate
bus voltages.
Independent TK/SS pins for each controller ramp the
output voltages during start-up. Current foldback limits
MOSFET heat dissipation during short-circuit condi-
tions. The MODE/PLLIN pin selects among Burst Mode
operation, pulse-skipping mode, or continuous inductor
current mode and allows the IC to be synchronized to an
external clock.
The LTC3850 is available in low profile 28-pin 4mm × 4mm,
4mm × 5mm QFN and narrow SSOP packages.
20k
43.2k
Synchronous Step-Down
2.2k
38501 TA01
2.2µH
22µF
50V
®
3850 is a high performance dual synchronous
®
V
7V TO
24V
IN
compensation allows the transient response
100µF
6V
Switching Controller
V
2.5V
5A
OUT2
LTC3850/LTC3850-1
100
95
90
85
80
75
70
65
60
55
50
10
Dual, 2-Phase
V
V
IN
OUT
= 12V
= 3.3V
LOAD CURRENT (mA)
100
Efficiency
POWER LOSS
EFFICIENCY
1000
38501 TA01b
10000
10000
1000
100
10
38501fc
1
®

Related parts for LTC3850EUF#PBF

LTC3850EUF#PBF Summary of contents

Page 1

... Battery-Operated Digital Devices n DC Power Distribution Systems n L, LT, LTC, LTM, OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258. TYPICAL APPLICATION High Efficiency Dual 3 ...

Page 2

LTC3850/LTC3850-1 ABSOLUTE MAXIMUM RATINGS Input Supply Voltage (V ) ......................... 28V to –0.3V IN Input Supply Voltage ( LTC3850I Only ....................................... 30V to –0.3V Input Supply Transient Voltage (V IN INTV ≥ 5V, LTC3850I Only ................... 34V to ...

Page 3

... LEAD FREE FINISH TAPE AND REEL LTC3850EGN#PBF LTC3850EGN#TRPBF LTC3850EGN-1#PBF LTC3850EGN-1#TRPBF LTC3850IGN#PBF LTC3850IGN#TRPBF LTC3850IGN-1#PBF LTC3850IGN-1#TRPBF LTC3850EUF#PBF LTC3850EUF#TRPBF LTC3850EUFD#PBF LTC3850EUFD#TRPBF LTC3850IUF#PBF LTC3850IUF#TRPBF LTC3850IUFD#PBF LTC3850IUFD#TRPBF Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based finish parts. ...

Page 4

LTC3850/LTC3850-1 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER Main Control Loops V Regulated Feedback Voltage FB1,2 I Feedback Current FB1,2 V Reference Voltage Line Regulation REFLNREG V Output Voltage Load Regulation LOADREG g Transconductance Amplifier g ...

Page 5

ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER Oscillator and Phase-Locked Loop f Nominal Frequency NOM f Lowest Frequency LOW f Highest Frequency HIGH R MODE/PLLIN Input Resistance MODE/PLLIN I Phase Detector Output Current FREQ Sinking Capability ...

Page 6

LTC3850/LTC3850-1 TYPICAL PERFORMANCE CHARACTERISTICS Load Step (Burst Mode Operation) I LOAD 2A/DIV 200mA TO 2. 2A/DIV V OUT 100mV/DIV AC COUPLED 40µs/DIV CIRCUIT OF FIGURE 12V 1.8V IN OUT Load Step (Pulse-Skipping Mode) ...

Page 7

TYPICAL PERFORMANCE CHARACTERISTICS Tracking Up and Down with External Ramp TK/SS1 TK/SS2 2V/DIV V OUT1 3.3V 3Ω LOAD 1V/DIV V OUT2 1.8V 1.5Ω LOAD 1V/DIV 38501 G10 10ms/DIV Current Sense Threshold vs I Voltage INTV LIM ...

Page 8

LTC3850/LTC3850-1 TYPICAL PERFORMANCE CHARACTERISTICS Shutdown (RUN) Threshold vs Temperature 1.5 1.4 1.3 ON 1.2 OFF 1.1 1.0 –50 – TEMPERATURE (°C) 38501 G18 Undervoltage Lockout Threshold (INTV ) vs Temperature RISING 3 FALLING ...

Page 9

PIN FUNCTIONS (GN/UF/UFD) RUN1, RUN2 (Pins 1, 13/Pins 26, 9/Pins 27, 10): Run Control Inputs. A voltage above 1.2V on either pin turns on the IC. However, forcing either of these pins below 1.2V causes the IC to shut down ...

Page 10

LTC3850/LTC3850-1 PIN FUNCTIONS MODE/PLLIN (Pin 27/Pin 24/Pin 25): Force Continuous Mode, Burst Mode, or Pulse-Skipping Mode Selection Pin and External Synchronization Input to Phase Detector Pin. Connect this pin to SGND to force both channels into the continuous mode of ...

Page 11

OPERATION Main Control Loop The LTC3850 is a constant-frequency, current mode step- down controller with two channels operating 180 degrees out-of-phase. During normal operation, each top MOSFET is turned on when the clock for that channel sets the RS latch, ...

Page 12

LTC3850/LTC3850-1 OPERATION When a controller is enabled for Burst Mode operation, the peak current in the inductor is set to approximately one-third of the maximum sense voltage even though the voltage on the I pin indicates a lower value. If ...

Page 13

APPLICATIONS INFORMATION The Typical Application on the first page is a basic LTC3850 application circuit. LTC3850 can be configured to use either DCR (inductor resistance) sensing or low value resistor sensing. The choice between the two current sensing schemes is ...

Page 14

LTC3850/LTC3850-1 APPLICATIONS INFORMATION close to the switching node, to prevent noise from coupling into sensitive small-signal nodes. The capacitor C1 should be placed close to the IC pins. Low Value Resistors Current Sensing A typical sensing circuit using a discrete ...

Page 15

APPLICATIONS INFORMATION V SENSE 20mV/DIV 500ns/DIV Figure 3. Voltage Waveform Measured Directly Across the Sense Resistor. V SENSE 20mV/DIV 500ns/DIV Figure 4. Voltage Waveform Measured After the Sense Resistor Filter 1000pF , R F Inductor DCR Sensing For ...

Page 16

LTC3850/LTC3850-1 APPLICATIONS INFORMATION Ensure that R1 has a power rating higher than this value. If high efficiency is necessary at light loads, consider this power loss when deciding whether to use DCR sensing or sense resistors. Light load power loss ...

Page 17

APPLICATIONS INFORMATION voltage and maximum output current. Miller capacitance can be approximated from the gate charge curve MILLER usually provided on the MOSFET manufacturers’ data sheet equal to the increase in gate charge MILLER along the ...

Page 18

LTC3850/LTC3850-1 APPLICATIONS INFORMATION selected mode once TK/SS > 0.74V. The output ripple is minimized during the 100mV forced continuous mode window ensuring a clean PGOOD signal. When the channel is configured to track another supply, the feedback voltage of the ...

Page 19

APPLICATIONS INFORMATION TIME (5a) Coincident Tracking Figure 5. Two Different Modes of Output Voltage Tracking V OUT1 TK/SS2 PIN R4 R2 (6a) Coincident Tracking Setup Figure 6. Setup for Coincident and Ratiometric Tracking V OUT1 V OUT2 ...

Page 20

LTC3850/LTC3850-1 APPLICATIONS INFORMATION exceeded. The INTV current, which is dominated by the CC gate charge current, may be supplied by either the 5V linear regulator or EXTV . When the voltage on the EXTV CC is less than 4.7V, the ...

Page 21

APPLICATIONS INFORMATION turns on the topside switch. The switch node voltage, SW, rises to V and the BOOST pin follows. With the topside IN MOSFET on, the boost voltage is above the input supply ...

Page 22

LTC3850/LTC3850-1 APPLICATIONS INFORMATION suggested. A 2.2Ω – 10Ω resistor placed between C (C1) and the V pin provides further isolation between IN the two channels. The selection driven by the effective series OUT resistance (ESR). Typically, once ...

Page 23

APPLICATIONS INFORMATION 900 800 700 600 500 400 300 200 100 0 0 0.5 1 1.5 FREQ/PLLFLTR PIN VOLTAGE (V) Figure 10. Relationship Between Oscillator Frequency and Voltage at the FREQ/PLLFLTR Pin MODE/ PLLIN DIGITAL EXTERNAL PHASE/ OSCILLATOR FREQUENCY DETECTOR ...

Page 24

LTC3850/LTC3850-1 APPLICATIONS INFORMATION Although all dissipative elements in the circuit produce losses, four main sources usually account for most of the losses in LTC3850 circuits regulator current losses, 4) Topside MOSFET transition losses. ...

Page 25

APPLICATIONS INFORMATION pin. The bandwidth can also be estimated by examining the rise time at the pin. The I external components shown TH in the Typical Application circuit will provide an adequate starting point for most applications. The I series ...

Page 26

LTC3850/LTC3850-1 APPLICATIONS INFORMATION f IN Figure 12. Recommended Printed Circuit Layout Diagram BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH TK/SS1 PU2 V PULL-UP PGOOD I PGOOD TH1 ...

Page 27

APPLICATIONS INFORMATION 5. Is the INTV decoupling capacitor connected close CC to the IC, between the INTV and the power ground CC pins? This capacitor carries the MOSFET drivers current peaks. An additional 1µF ceramic capacitor placed im- mediately next ...

Page 28

LTC3850/LTC3850-1 APPLICATIONS INFORMATION 4.7µF M1 0.1µF L1 3.3µH 6.19k 1% 1.33k 1% 33pF V OUT1 3.3V 5A 63.4k 1% 1800pF C 20k 4.75k OUT1 100µ L1, L2: COILTRONICS HCP0703 M1, M2: VISHAY SILICONIX Si4816BDY ...

Page 29

APPLICATIONS INFORMATION The Coiltronics (Cooper) HCP0703-2R2 (20mΩ DCR at 20°C) and HCP0703-3R3 (30mΩ DCR chosen. At 100°C, the estimated maximum DCR values are 26.4mΩ and 39.6mΩ. The divider ratios are: R 7mΩ SENSE(EQUIV DCR at T ...

Page 30

LTC3850/LTC3850-1 TYPICAL APPLICATIONS 4.7µ 2.2µH 8mΩ 15pF V OUT1 3.3V 5A 63.4k 1% 1000pF + 20k C 10k OUT1 1% 1% 220µF L1: TDK RLF 7030T-2R2M5R4 L2: TDK ULF10045T-3R3N6R9 C : SANYO 4TPE220MF OUT1 C : SANYO 6TPE150MI ...

Page 31

TYPICAL APPLICATIONS LTC3850/LTC3850-1 31 38501fc ...

Page 32

LTC3850/LTC3850-1 TYPICAL APPLICATIONS 32 38501fc ...

Page 33

TYPICAL APPLICATIONS 4.7µF M1 0.1µF L1 0.75µH 1.2k 1% 2.94k 1% 47pF V OUT1 1.8V 5A 25.5k 1% 2200pF C 20k 14k OUT1 100µ L1, L2: TOKO FDV0630 0.75µH M1, M2: VISHAY SILICONIX Si4816BDY ...

Page 34

LTC3850/LTC3850-1 PACKAGE DESCRIPTION .254 MIN .0165 ± .0015 RECOMMENDED SOLDER PAD LAYOUT .0075 – .0098 (0.19 – 0.25) .016 – .050 (0.406 – 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) 3. DRAWING NOT TO SCALE ...

Page 35

SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 ± 0.10 (4 SIDES) PIN 1 TOP MARK (NOTE 6) NOTE: 1. DRAWING ...

Page 36

LTC3850/LTC3850-1 PACKAGE DESCRIPTION 4.50 ± 0.05 3.10 ± 0.05 2.50 REF 2.65 ± 0.05 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED PIN 1 TOP MARK (NOTE 6) 5.00 ...

Page 37

... Updated Switch Voltage (SW1, SW2) LTC3850I only from 30V to –0.3V to 30V to –5V Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...

Page 38

... LTC3834/ Low I , Synchronous Step-Down Controller Q LTC3834-1 LT3845 Low I , High Voltage Single Output Synchronous Step-Down Q DC/DC Controller PolyPhase is a registered trademark of Linear Technology Corporation Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 l 10k RUN 0.1µF RUN1 FREQ ...

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