Selectable Continuous, Pulse-Skipping or Low Ripple
Burst Mode
®
Operation at Light Loads
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Output Voltage Soft-Start or Tracking
Power Good Output Voltage Monitor
Output Overvoltage Protection
Low Shutdown I
Q
: <14µA
Internal LDO Powers Gate Drive from V
IN
or EXTV
CC
No Current Foldback During Start-Up
Narrow SSOP Package
APPLICATIONS
n
n
n
Automotive Always-On Systems
Battery Operated Digital Devices
Distributed DC Power Systems
TYPICAL APPLICATION
High Efficiency Dual 8.5V/3.3V Output Step-Down Converter
4.7µF
TG1
4.7µH
0.1µF
V
IN
INTV
CC
TG2
22µF
V
IN
9V TO 60V
100
Efficiency and Power Loss
vs Output Current
V
IN
= 12V
90 V
OUT
= 3.3V
80
70
60
50
40
30
20
1
0.1
10
38901 TA01b
10000
1000
POWER LOSS (mW)
BOOST1
SW1
BG1
LTC3890-1
BOOST2
SW2
BG2
PGND
SENSE2
+
0.1µF
8µH
EFFICIENCY (%)
100
10
SENSE1
+
0.008Ω
V
OUT1
3.3V
5A
SENSE1
–
V
FB1
ITH1
1000pF
31.6k
34.8k
0.01Ω
SENSE2
–
V
FB2
ITH2
1000pF
34.8k
0.1µF
V
OUT2
8.5V
3A
330µF
10
0
0.0001
0.001
0.01
0.1
1
OUTPUT CURRENT (A)
100k
470µF
100k
10.5k
TRACK/SS1 SGND TRACK/SS2
0.1µF
38901 TA01a
38901fb
1
LTC3890-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
ITH1
V
FB1
SENSE1
+
Input Supply Voltage (V
IN
) ......................... –0.3V to 65V
Topside Driver Voltages
BOOST1, BOOST2 ..................................–0.3V to 71V
Switch Voltage (SW1, SW2) ......................... –5V to 65V
(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
PLLIN/MODE, INTV
CC
Voltages ................... –0.3V to 6V
FREQ Voltage ........................................ –0.3V to INTV
CC
EXTV
CC
..................................................... –0.3V to 14V
ITH1, ITH2, V
FB1
, V
FB2
Voltages ................... –0.3V to 6V
PGOOD1 Voltage ......................................... –0.3V to 6V
TRACK/SS1, TRACK/SS2 Voltages ............. –0.3V to 6V
Operating Junction Temperature Range (Notes 2, 3)
LTC3890E-1, LTC3890I-1 ................... –40°C to 125°C
LTC3890H-1 ....................................... –40°C to 150°C
LTC3890MP-1 .................................... –55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
1
2
3
4
5
6
7
8
9
11
28 TRACK/SS1
27 PGOOD1
26 TG1
25 SW1
24 BOOST1
23 BG1
22 V
IN
21 PGND
20 EXTV
CC
19 INTV
CC
18 BG2
17 BOOST2
16 SW2
15 TG2
SENSE1
–
FREQ
PLLIN/MODE
SGND
RUN1
RUN2
SENSE2
+
SENSE2
–
10
V
FB2
12
ITH2 13
TRACK/SS2 14
GN PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 150°C,
θ
JA
= 90°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3890EGN-1#PBF
LTC3890IGN-1#PBF
LTC3890HGN-1#PBF
LTC3890MPGN-1#PBF
TAPE AND REEL
LTC3890EGN-1#TRPBF
LTC3890IGN-1#TRPBF
LTC3890HGN-1#TRPBF
LTC3890MPGN-1#TRPBF
PART MARKING*
LTC3890GN-1
LTC3890GN-1
LTC3890GN-1
LTC3890GN-1
PACKAGE DESCRIPTION
28-Lead Plastic SSOP
28-Lead Plastic SSOP
28-Lead Plastic SSOP
28-Lead Plastic SSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
38901fb
2
LTC3890-1
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
FB1,2
PARAMETER
Input Supply Operating Voltage Range
Regulated Feedback Voltage
I
TH1,2
Voltage = 1.2V (Note 4)
–40°C to 85°C, All Grades
LTC3890E-1, LTC3890I-1,
LTC3890H-1, LTC3890MP-1
(Note 4)
V
IN
= 4.5V to 60V (Note 4)
(Note 4)
Measured in Servo Loop,
∆
ITH
Voltage = 1.2V to 0.7V
(Note 4)
Measured in Servo Loop,
∆
ITH
Voltage = 1.2V to 2V
g
m1,2
I
Q
Transconductance Amplifier g
m
Input DC Supply Current
Pulse-Skipping or Forced Continuous
Mode (One Channel On)
Pulse-Skipping or Forced Continuous
Mode (Both Channels On)
Sleep Mode (One Channel On)
Sleep Mode (Both Channels On)
Shutdown
UVLO
V
OVL
I
SENSE+
I
SENSE–
DF
MAX
I
TRACK/SS1,2
V
RUN1
On
V
RUN2
On
V
SENSE(MAX)
Gate Driver
TG1,2
BG1,2
Pull-Up On-Resistance
Pull-Down On-Resistance
Pull-Up On-Resistance
Pull-Down On-Resistance
TG Transition Time:
Rise Time
Fall Time
BG Transition Time:
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
2.5
1.5
2.4
1.1
25
25
25
25
Ω
Ω
Ω
Ω
ns
ns
ns
ns
38901fb
The
l
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
RUN1,2
= 5V, EXTV
CC
= 0V unless otherwise noted. (Note 2)
CONDITIONS
MIN
4
0.792
0.788
0.786
0.800
0.800
0.800
±5
0.002
l
TYP
MAX
60
0.808
0.812
0.812
±50
0.02
0.1
UNITS
V
V
V
V
nA
%/V
%
l
l
I
FB1,2
V
REFLNREG
V
LOADREG
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
0.01
l
–0.01
2
2
2
50
60
14
–0.1
%
mmho
mA
mA
I
TH1,2
= 1.2V, Sink/Source = 5µA (Note 4)
(Note 5)
RUN1 = 5V and RUN2 = 0V, V
FB1
= 0.83V or
RUN1 = 0V and RUN2 = 5V, V
FB2
= 0.83V
RUN1,2 = 5V, V
FB1,2
= 0.83V (No Load)
RUN1 = 5V and RUN2 = 0V, V
FB1
= 0.83V or
RUN1 = 0V and RUN2 = 5V, V
FB2
= 0.83V
RUN1,2 = 5V, V
FB1,2
= 0.83V (No Load)
RUN1,2 = 0V
INTV
CC
Ramping Up
INTV
CC
Ramping Down
Measured at V
FB1,2
, Relative to Regulated V
FB1,2
Each Channel
Each Channel
V
SENSE–
< INTV
CC
– 0.5V
V
SENSE–
> INTV
CC
+ 0.5V
In Dropout
V
TRACK1,2
= 0V
V
RUN1
Rising
V
RUN2
Rising
V
FB1,2
= 0.7V, V
SENSE1
–,
2
– = 3.3V, I
LIM
= 0
l
l
l
l
75
100
25
4.2
4.0
13
±1
±1
µA
µA
µA
V
V
%
µA
µA
µA
%
µA
V
V
mV
mV
Undervoltage Lockout
Feedback Overvoltage Protection
SENSE
+
Pin Current
SENSE
–
Pins Current
3.6
7
3.92
3.80
10
700
98
0.7
1.15
1.20
64
99
1.0
1.21
1.25
50
l
Maximum Duty Factor
Soft-Start Charge Current
RUN1 Pin On Threshold
RUN2 Pin On Threshold
Maximum Current Sense Threshold
1.4
1.27
1.30
85
V
RUN1,2
Hyst RUN Pin Hysteresis
75
TG1,2 t
r
TG1,2 t
f
BG1,2 t
r
BG1,2 t
f
3
LTC3890-1
ELECTRICAL CHARACTERISTICS
SYMBOL
TG/BG t
1D
BG/TG t
1D
t
ON(MIN)
V
INTVCCVIN
V
LDOVIN
V
INTVCCEXT
V
LDOEXT
V
EXTVCC
V
LDOHYS
f
25kΩ
f
65kΩ
f
105kΩ
f
LOW
f
HIGH
f
SYNC
V
PGL
I
PGOOD
V
PG
PARAMETER
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
Minimum On-Time
Internal V
CC
Voltage
INTV
CC
Load Regulation
Internal V
CC
Voltage
INTV
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Hysteresis
Programmable Frequency
Programmable Frequency
Programmable Frequency
Low Fixed Frequency
High Fixed Frequency
Synchronizable Frequency
PGOOD1 Voltage Low
PGOOD1 Leakage Current
PGOOD1 Trip Level
R
FREQ
= 25k, PLLIN/MODE = DC Voltage
R
FREQ
= 65k, PLLIN/MODE = DC Voltage
R
FREQ
= 105k, PLLIN/MODE = DC Voltage
V
FREQ
= 0V, PLLIN/MODE = DC Voltage
V
FREQ
= INTV
CC
, PLLIN/MODE = DC Voltage
PLLIN/MODE = External Clock
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Negative
Hysteresis
V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Positive
Hysteresis
t
PG
Delay for Reporting a Fault
–13
–10
2.5
10
2.5
25
l
The
l
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
RUN1,2
= 5V, EXTV
CC
= 0V unless otherwise noted. (Note 2)
CONDITIONS
C
LOAD
= 3300pF Each Driver
C
LOAD
= 3300pF Each Driver
(Note 7)
6V < V
IN
< 60V, V
EXTVCC
= 0V
I
CC
= 0mA to 50mA, V
EXTVCC
= 0V
6V < V
EXTVCC
< 13V
I
CC
= 0mA to 50mA, V
EXTVCC
= 8.5V
EXTV
CC
Ramping Positive
4.5
4.85
4.85
MIN
TYP
30
30
95
5.1
0.7
5.1
0.6
4.7
250
105
375
320
485
75
0.2
440
835
350
535
380
585
850
0.4
±1
–7
505
5.35
1.1
5.35
1.1
4.9
MAX
UNITS
ns
ns
ns
V
%
V
%
V
mV
kHz
kHz
kHz
kHz
kHz
kHz
V
µA
%
%
%
%
µs
INTV
CC
Linear Regulator
Oscillator and Phase-Locked Loop
PGOOD1 Output
7
13
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Ratings for extended periods may affect device reliability and
lifetime.
Note 2:
The LTC3890-1 is tested under pulsed load condition such that
T
J
≈ T
A
.The LTC3890E-1 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3890I-1 is guaranteed
over the –40°C to 125°C operating junction temperature range, the
LTC3890H-1 is guaranteed over the –40°C to 150°C operating junction
temperature range and the LTC3890MP-1 is tested and guaranteed over
the –55°C to 150°C operating junction temperature range.
High junction temperatures degrade operating lifetimes; operating lifetime
is derated for junction temperatures greater than 125°C. Note that the
maximum ambient temperature consistent with these specifications is
determined by specific operating conditions in conjunction with board layout,
the rated package thermal impedance and other environmental factors.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• 90°C/W)
Note 4:
The LTC3890-1 is tested in a feedback loop that servos V
ITH1,2
to
a specified voltage and measures the resultant V
FB
. The specification at
85°C is not tested in production and is assured by design, characterization
and correlation to production testing at other temperatures (125°C for the
LTC3890E-1/LTC3890I-1, 150°C for the LTC3890H-1/LTC3890MP-1). For
the LTC3890MP-1, the specification at –40°C is not tested in production
and is assured by design, characterization and correlation to production
testing at –55°C.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See the Applications information section.
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7:
The minimum on-time condition is specified for an inductor peak-
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