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LTC3858IUH#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P38
LTC3858
1
3858fc
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
Low I
Q
, Dual
2-Phase Synchronous
Step-Down Controller
High Effi ciency Dual 8.5V/3.3V Step-Down Converter
n
Low Operating I
Q
: 170μA (One Channel On)
n
Wide Output Voltage Range: 0.8V ≤ V
OUT
≤ 24V
n
Wide V
IN
Range: 4V to 38V
n
R
SENSE
or DCR Current Sensing
n
Out-of-Phase Controllers Reduce Required Input
Capacitance and Power Supply Induced Noise
n
OPTI-LOOP
®
Compensation Minimizes C
OUT
n
Phase-Lockable Frequency (75kHz-850kHz)
n
Programmable Fixed Frequency (50kHz-900kHz)
n
Selectable Continuous, Pulse-Skipping or
Burst Mode
®
Operation at Light Loads
n
Very Low Dropout Operation: 99% Duty Cycle
n
Adjustable Output Voltage Soft-Start
n
Power Good Output Voltage Monitor
n
Output Overvoltage Protection
n
Output Latch-Off Protection During Short Circuit
n
Low Shutdown I
Q
: 8µA
n
Internal LDO Powers Gate Drive from V
IN
or EXTV
CC
n
No Current Foldback During Start-Up
n
Small 5mm × 5mm QFN Package
n
Automotive Systems
n
Battery Operated Digital Devices
n
Distributed DC Power Systems
Effi ciency and Power Loss
vs Load Current
The LTC
®
3858 is a high performance dual step-down
switching regulator controller that drives all N-channel
synchronous power MOSFET stages. A constant frequency
current mode architecture allows a phase-lockable fre-
quency of up to 850kHz. Power loss and noise due to the
input capacitor ESR are minimized by operating the two
controller outputs out of phase.
The 170A no-load quiescent current extends operating
life in battery-powered systems. OPTI-LOOP compensa-
tion allows the transient response to be optimized over
a wide range of output capacitance and ESR values. The
LTC3858 features a precision 0.8V reference and a power
good output indicator. A wide 4V to 38V input supply range
encompasses a wide range of intermediate bus voltages
and battery chemistries.
Independent soft-start pins for each controller ramp the
output voltages during start-up. The output latch-off feature
protects the circuit in short-circuit conditions.
For a leaded 28-lead SSOP package with a fi xed current
limit and one PGOOD output, without phase modulation
or a clock output, see the LTC3858-1 data sheet.
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, µModule, PolyPhase, Linear Technology and the Linear
logo are registered trademarks and No R
SENSE
and UltraFast are 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.
0.1µF
62.5k
3.3µH
680pF
150µF
4.7µF
22µF
50V
0.007Ω
20k
15k
V
OUT1
3.3V
5A
150µF
0.1µF
193k
7.2µH
680pF
0.01Ω
20k
15k
V
OUT2
8.5V
3.5A
TG1 TG2
BOOST1 BOOST2
SW1 SW2
BG1 BG2
SGND
PGND
SENSE1
+
SENSE2
+
SENSE1
–
SENSE2
–
V
FB1
V
FB2
I
TH1
I
TH2
V
IN
INTV
CC
SS1 SS2
V
IN
9V TO 38V
3858 TA01
0.1µF
0.1µF
LTC3858
OUTPUT CURRENT (A)
0.0001
40
EFFICIENCY (%)
POWER LOSS (mW)
50
60
70
80
0.001 0.01 0.1 1 10
3858 TA01b
30
20
10
0
90
100
10
100
1000
1
0.1
10000
EFFICIENCY
POWER LOSS
V
IN
= 12V
V
OUT
= 3.3V
FIGURE 12 CIRCUIT
LTC3858
2
3858fc
PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS
(Note 1)
32 31 30 29 28 27 26 25
9 10 11 12 13 14 15 16
17
18
19
20
21
22
23
24
8
7
6
5
4
3
2
1
TOP VIEW
SENSE1
–
FREQ
PHASMD
CLKOUT
PLLIN/MODE
SGND
RUN1
RUN2
BOOST1
BG1
V
IN
PGND
EXTV
CC
INTV
CC
BG2
BOOST2
SENSE1
+
V
FB1
I
TH1
SS1
I
LIM
PGOOD1
TG1
SW1
SENSE2
–
SENSE2
+
V
FB2
I
TH2
SS2
PGOOD2
TG2
SW2
UH PACKAGE
32-LEAD (5mm s 5mm) PLASTIC QFN
33
SGND
T
JMAX
= 125°C, θ
JA
= 34°C/W
EXPOSED PAD (PIN 33) IS SGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3858EUH#PBF LTC3858EUH#TRPBF 3858
32-Lead (5mm × 5mm) Plastic QFN
–40°C to 125°C
LTC3858IUH#PBF LTC3858IUH#TRPBF 3858
32-Lead (5mm × 5mm) Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to:
http://www.linear.com/tapeandreel/
Input Supply Voltage (V
IN
) ......................... –0.3V to 40V
Topside Driver Voltages
BOOST1, BOOST2 ................................. –0.3V to 46V
Switch Voltage (SW1, SW2) ........................ –5V to 40V
PLLIN/MODE,(BOOST1-SW1),
(BOOST2-SW2) ........................................... –0.3V to 6V
RUN1, RUN2 ............................................... –0.3V to 8V
Maximum Current Sourced into Pin
from Source >8V...............................................100µA
SENSE1
+
, SENSE2
+
, SENSE1
–
SENSE2
–
Voltages ...................................... –0.3V to 28V
FREQ Voltages ..................................... –0.3V to INTV
CC
I
LIM
, PHASMD Voltages ....................... –0.3V to INTV
CC
EXTV
CC
...................................................... –0.3V to 14V
I
TH1
, I
TH2
,V
FB1
, V
FB2
Voltages ...................... –0.3V to 6V
PGOOD1, PGOOD2 Voltages ....................... –0.3V to 6V
SS1, SS2, INTV
CC
Voltages ......................... –0.3V to 6V
Operating Junction Temperature Range
(Note 2) .................................................. –40°C to 125°C
Maximum Junction Temperature (Note 3) ............ 125°C
Storage Temperature Range ................... –65°C to 150°C
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Input Supply Operating Voltage Range 4 38 V
V
FB1,2
Regulated Feedback Voltage (Note 4) I
TH1,2
= 1.2V
–40°C to 125°C
–40°C to 85°C
l
0.788
0.792
0.800
0.800
0.812
0.808
V
V
I
FB1,2
Feedback Current (Note 4) ±5 ±50 nA
V
REFLNREG
Reference Voltage Line Regulation (Note 4) V
IN
= 4.5V to 38V 0.002 0.02 %/V
The l denotes the specifi cations which apply over the full operating
junction temperature range, otherwise specifi cations are at T
A
= 25°C (Note 2). V
IN
= 12V, V
RUN1,2
= 5V, EXTV
CC
= 0V unless
otherwise noted.
LTC3858
3
3858fc
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
LOADREG
Output Voltage Load Regulation (Note4)
Measured in Servo Loop,
∆I
TH
Voltage = 1.2V to 0.7V
l
0.01 0.1 %
(Note4)
Measured in Servo Loop,
∆I
TH
Voltage = 1.2V to 2V
l
–0.01 –0.1 %
g
m1,2
Transconductance Amplifi er g
m
(Note 4) I
TH1,2
= 1.2V, Sink/Source = 5µA 2 mmho
I
Q
Input DC Supply Current (Note 5)
Pulse Skip or Forced Continuous Mode
(One Channel On)
RUN1 = 5V and RUN2 = 0V, V
FB1
= 0.83V (No Load) or
RUN1 = 0V and RUN2 = 5V, V
FB2
= 0.83V (No Load)
1.3 mA
Pulse Skip or Forced Continuous Mode
(Both Channels On)
RUN1,2 = 5V, V
FB1,2
= 0.83V (No Load) 2 mA
Sleep Mode (One Channel On) RUN1 = 5V and RUN2 = 0V, V
FB1
= 0.83V (No Load) or
RUN1 = 0V and RUN2 = 5V, V
FB2
= 0.83V (No Load)
170 250 µA
Sleep Mode (Both Channels On) RUN1,2 = 5V, V
FB1,2
= 0.83V (No Load) 300 450 µA
Shutdown RUN1,2 = 0V 8 20 µA
UVLO Undervoltage Lockout INTV
CC
Ramping Up
INTV
CC
Ramping Down
l
l
3.6
4.0
3.8
4.2
4
V
V
V
OVL
Feedback Overvoltage Protection Measured at V
FB1,2
, Relative to Regulated V
FB1,2
71013 %
I
SENSE
+
SENSE
+
Pin Current Each Channel ±1 µA
I
SENSE
–
SENSE
–
Pin Current Each Channel
V
OUT1,2
< INTV
CC
– 0.5V
V
OUT1,2
> INTV
CC
+ 0.5V 550
±1
950
µA
µA
DF
MAX
Maximum Duty Factor In Dropout, FREQ = 0V 98 99.4 %
I
SS1,2
Soft-Start Charge Current V
SS1,2
= 0V 0.7 1.0 1.4 µA
V
RUN1,2
On RUN Pin On Threshold Voltage V
RUN1
, V
RUN2
Rising
l
1.23 1.28 1.33 V
V
RUN1,2
Hyst RUN Pin Hysteresis Voltage 50 mV
V
SS1,2
LA SS Pin Latch-Off Arming Threshold Voltage V
SS1
, V
SS2
Rising from 1V 1.9 2 2.1 V
V
SS1,2
LT SS Pin Latch-Off Threshold Voltage V
SS1
, V
SS2
Falling from 2V 1.3 1.5 1.7 V
I
DSC1,2
LT SS Discharge Current Short-Circuit Condition V
FB1,2
= 0V,
V
SS1,2
= 5V
71013 µA
V
SENSE(MAX)
Maximum Current Sense Threshold Voltage V
FB1,2
= 0.7V, V
SENSE1
–,
2
– = 3.3V, I
LIM
= 0
V
FB1,2
= 0.7V, V
SENSE1
–,
2
– = 3.3V, I
LIM
= FLOAT
V
FB1,2
= 0.7V, V
SENSE1
–,
2
– = 3.3V, I
LIM
= INTV
CC
l
l
l
22
43
64
30
50
75
36
57
86
mV
mV
mV
Gate Driver
TG1,2 Pull-Up On-Resistance
Pull-Down On-Resistance
2.5
1.5
BG1,2 Pull-Up On-Resistance
Pull-Down On-Resistance
2.4
1.1
TG1,2 t
r
TG1,2 t
f
TG Transistion Time:
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
25
16
ns
ns
BG1,2 t
r
BG1,2 t
f
BG Transistion Time:
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
28
13
ns
ns
TG/BG t
1D
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
C
LOAD
= 3300pF Each Driver 30 ns
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
junction temperature range, otherwise specifi cations are at T
A
= 25°C (Note 2). V
IN
= 12V, V
RUN1,2
= 5V, EXTV
CC
= 0V unless
otherwise noted.
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LTC3858IUH#TRPBF

Mfr. #:
Buy LTC3858IUH#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Low IQ, Dual, 2-Phase Synchronous Step-Down Controller
Lifecycle:
New from this manufacturer.
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