ler specially designed for multiphase operation with LTC's
digital power system management DC/DC controllers. It
provides a small and cost effective solution for supply-
ing very large currents by cascading it with a LTC3887-1
controller. A peak current mode architecture provides the
LTC3870-1 with excellent current sharing from phase to
phase and from chip to chip.
Coherently working with the LTC3887-1, the LTC3870-1
does not require additional I
2
C addresses, and it supports
all programmable features as well as fault protection.
The constant switching frequency can be synchronized
to an external clock from the LTC3887-1 over a range of
100kHz to 1MHz.
L,
LT, LTC, LTM, PolyPhase, Linear Technology and the Linear logo 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, 6144194, 6177787,
6580258, 5408150
n
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LTC3887-1 Phase Extender
Operates with Power Blocks, DrMOS or External
Gate Drivers and MOSFETs
Cascade with Multiple Chips for Very Large Current
Applications
Accurate PolyPhase Current Sharing
EXTV
CC
Capable of 5V to 14V Input
Wide V
IN
Range: 4.5V to 60V
Wide Output Voltage Range : 0.5V to 14V
Wide SYNC Frequency Range: 100kHz to 1MHz
Pin Programmable CCM/DCM Operation
Pin Programmable Phase-Shift Control
Available in a 24-Pin (4mm
×
4mm) QFN Package
applicaTions
n
n
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High Power Distributed Power Systems
Telecom Systems
Industrial Applications
Typical applicaTion
V
IN
7V TO 14V
22µF
4.7µF
V
IN
INTV
CC
V
CC0
V
OUT0
3.3V, 30A
530µF
1.0µH
DrMOS
2.15k
0.2µF
I
SENSE0
+
I
SENSE0
-
LTC3887-1
RUN0
RUN1
3.3V
V
SENSE0
+ GPIO0
GPIO1
1.8V
V
SENSE1
+
I
TH0
I
TH1
SYNC
* REFER TO LTC3887-1 DATA SHEET
FOR MASTER SETUP
RUN0
RUN1
FAULT0
FAULT1
I
TH0
I
TH1
SYNC
I
SENSE1
+
I
SENSE1
-
EXTV
CC
FREQ
PHASMD
I
LIM
MODE0
MODE1
GND
82.5k
PWM0
PWM1
DrMOS
1.74k
0.2µF
V
CC1
LTC3870-1
0.56µH
V
OUT1
1.8V, 40A
530µF
Load Transient Response of a
2-Phase Master (3887-1)/Slave
(3870-1) Converter
I
LOAD
20A/DIV
10A TO 20A TO 10A
I
L
LTC3887–1
(CH0)
10A/DIV
I
L
LTC3870–1
(CH0)
10A/DIV
V
OUT
200mV/DIV
AC–COUPLED
V
IN
= 12V
V
OUT
= 1.8V
100µs/DIV
38701 TA01b
38701 TA01a
38701f
For more information
www.linear.com/LTC3870-1
1
LTC3870-1
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
FAULT0
FAULT1
MODE0
PWM0
18 V
CC0
17 V
IN
25
GND
16 GND
15 EXTV
CC
14 INTV
CC
13 V
CC1
7
MODE1
8
I
TH1
9 10 11 12
PHASMD
SYNC
I
LIM
PWM1
FREQ
I
TH0
V
IN
............................................................. –0.3V to 65V
V
CC0
, V
CC1
.................................................... –0.3V to 6V
I
SENSE0
+, I
SENSE0
−, I
SENSE1
+, I
SENSE1
− ....... –0.3V to 15V
INTV
CC
, RUN0/RUN1 .................................. –0.3V to 6V
EXTV
CC
.................................................... –0.3V to 14V
MODE0/MODE1,
FREQ, PHASMD, I
LIM
........................ –0.3V to INTV
CC
FAULT0/FAULT1,
I
TH0
/I
TH1
, SYNC .............. –0.3V to 3.6V
INTV
CC
, EXTV
CC
Peak Current (Note 7) ...............100mA
Operating Junction
Temperature Range............................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
24 23 22 21 20 19
I
SENSE0
I
SENSE0
+
–
1
2
RUN0 3
RUN1 4
I
SENSE1
–
5
I
SENSE1+
6
UF PACKAGE
24-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 46.9°C/W,
θ
JC_BOT
= 4.5°C/W
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3870EUF-1#PBF
LTC3870IUF-1#PBF
TAPE AND REEL
LTC3870EUF-1#TRPBF
LTC3870IUF-1#TRPBF
PART MARKING*
38701
38701
PACKAGE DESCRIPTION
24-Lead (4mm
×
4mm) Plastic QFN
24-Lead (4mm
×
4mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. (Note 2) V
IN
= 15V, V
RUN0,
V
RUN1
= 3.3V, f
SYNC
= 350kHz
(externally driven) unless otherwise specified.
SYMBOL
V
IN
V
OUT
I
Q
V
UVLO
CONTROL LOOP
I
ISENSE0
+,
I
ISENSE1
+
I
ISENSE0
–,
I
ISENSE1
–
Current Sense + Pin Current
Current Sense – Pin Current
V
ISENSE0,1
+ = 3.3V
V
ISENSE0,1
– = 3.3V
l
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elecTrical characTerisTics
PARAMETER
Input Voltage Range
Output Voltage Range
Input Voltage Supply Current
Normal Operation
Undervoltage Lockout Threshold
when V
IN
> 4.2V
CONDITIONS
(Note 3)
(Note 4)
V
RUN0
, V
RUN1
= 0V
V
RUN0
, V
RUN1
= 3.3V
V
INTVCC
Falling
V
INTVCC
Rising
MIN
4.5
0.5
TYP
MAX
60
14
UNITS
V
V
mA
mA
V
V
1.1
2.6
3.7
4.0
±0.1
±0.1
±1
±1
µA
µA
38701f
2
For more information
www.linear.com/LTC3870-1
LTC3870-1
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. (Note 2) V
IN
= 15V, V
RUN0,
V
RUN1
= 3.3V, f
SYNC
= 350kHz
(externally driven) unless otherwise specified.
SYMBOL
V
IILIMIT
PWM Outputs
PWM
PWM Output High Voltage
PWM Output Low Voltage
PWM Output Current in Hi-Z State
Minimum On-Time
Internal V
CC
Voltage No Load
INTV
CC
Load Regulation
Internal V
CC
Voltage No Load
EXTV
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Hysteresis
Oscillator SYNC Range
SYNC Input Threshold
Nominal Frequency
FREQ Setting Current
SYNC to Ch0 Phase Relationship Based on the
Falling Edge of SYNC and Rising Edge of PWM0
PHASMD =0
PHASMD = 1/3 INTV
CC
PHASMD = 2/3 INTV
CC
PHASMD = INTV
CC
PHASMD = 0
PHASMD = 1/3 INTV
CC
PHASMD = 2/3 INTV
CC
PHASMD = INTV
CC
l
l
l
elecTrical characTerisTics
PARAMETER
CONDITIONS
l
l
MIN
70
45
V
CC
– 0.2
–5
TYP
75
50
MAX
80
55
UNITS
mV
mV
V
V
µA
ns
Maximum Current Sense Threshold (High Range) V
ITH
= 2.22V, I
LIM
= INTV
CC
Maximum Current Sense Threshold (Low Range)
V
ITH
= 2.22V, I
LIM
= GND
I
LOAD
= 500µA
I
LOAD
= –500µA
(Note 5)
6.0V < V
IN
< 60V, V
EXTVCC
= 0V
I
CC
= 0mA to 50mA, V
EXTVCC
= 0V
V
EXTVCC
= 8.5V (Note 6)
I
CC
= 0mA to 20mA, V
EXTVCC
= 8.5V
V
EXTVCC
Ramping Positive (Note 6)
l
l
0.2
5
90
t
ON(MIN)
V
INTVCC_VIN
V
LDO
INT
V
INTVCC_EXT
V
LDO
EXT
V
EXTVCC
V
HYS_EXTVCC
f
SYNC
V
TH,SYNC
f
NOM
I
FREQ
θ
SYNC
-θ
0
INTV
CC
Regulator
4.85
4.85
4.65
5.1
0.8
5.1
0.5
4.8
200
100
0.4
2.0
500
9
10
180
60
120
90
0
300
240
270
2.0
1.4
11
1000
5.35
±2
5.35
±2
4.95
V
%
V
%
V
mV
kHz
V
V
kHz
µA
Deg
Deg
Deg
Deg
Deg
Deg
Deg
Deg
V
V
Oscillator and Phase-Locked Loop
V
TH,SYNC
Falling (Note 7)
V
TH,SYNC
Rising
V
FREQ
= 1.0V
θ
SYNC
-θ
1
SYNC to Ch1 Phase Relationship Based on the
Falling Edge of SYNC and Rising Edge of PWM1
Digital Inputs RUN0/RUN1, MODE0/MODE1,
FAULT0/FAULT1
V
IH
V
IL
Input High Threshold Voltage
Input Low Threshold Voltage
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC3870-1 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3870E-1 is guaranteed to meet specifications from
0°C to 85°C junction temperature. Specifications over the –40°C to
125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC3870I-1 is guaranteed over the full –40°C to 125°C operating
junction temperature range. Note that the maximum ambient temperature
consistent with these specifications is determined by specific operating
conditions in conjunction with board layout, the related package thermal
impedance and other environmental factors. The junction temperature 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
•
46.9°C/W)
Note 3:
When V
IN
>15V, EXTV
CC
is recommended to reduce IC Temperature.
Note 4:
Output voltage is set and controlled by the master controller in
multiphase operations.
Note 5:
The minimum on-time condition corresponds to an inductor
peak-to-peak ripple current ≥40% of I
MAX
(see Minimum On-Time
Considerations in the Applications Information section).
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