LTC2927C ................................................ 0°C to 70°C
LTC2927I.............................................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
Supply Voltage (V
CC
) ................................. –0.3V to 10V
Input Voltages
ON ......................................................... –0.3V to 10V
TRACK .........................................–0.3V to V
CC
+ 0.3V
Output Voltages
FB,
SDO
................................................. –0.3V to 10V
RAMP RAMPBUF .........................–0.3V to V
CC
+ 0.3V
,
PIN CONFIGURATION
TOP VIEW
TOP VIEW
ON 1
RAMP 2
RAMPBUF 3
TRACK 4
9
8 V
CC
7 SDO
6 FB
5 GND
V
CC
1
SDO 2
FB 3
GND 4
8 ON
7 RAMP
6 RAMPBUF
5 TRACK
DDB PACKAGE
8-LEAD (3mm
×
2mm) PLASTIC DFN
EXPOSED PAD (PIN 9) PCB GND, CONNECTION OPTIONAL
T
JMAX
= 125°C,
θ
JA
= 76°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC2927CDDB#PBF
LTC2927IDDB#PBF
LTC2927CTS8#PBF
LTC2927ITS8#PBF
LEAD BASED FINISH
LTC2927CDDB
LTC2927IDDB
LTC2927CTS8
LTC2927ITS8
TAPE AND REEL
LTC2927CDDB#TRPBF
LTC2927IDDB#TRPBF
LTC2927CTS8#TRPBF
LTC2927ITS8#TRPBF
TAPE AND REEL
LTC2927CDDB#TR
LTC2927IDDB#TR
LTC2927CTS8#TR
LTC2927ITS8#TR
PART MARKING*
LBQH
LBQH
LTBQJ
LTBQJ
PART MARKING*
LBQH
LBQH
LTBQJ
LTBQJ
PACKAGE DESCRIPTION
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
PACKAGE DESCRIPTION
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°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/
2
U
W W
W
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 250°C/W
2927fb
LTC2927
ELECTRICAL CHARACTERISTICS
SYMBOL
V
CC
I
CC
V
CC(UVLO)
ΔV
CC(UVHYST)
V
ON(TH)
ΔV
ON(HYST)
I
ON
I
RAMP
V
RAMPBUF(OL)
V
RAMPBUF(OH)
V
OS
I
ERROR(%)
V
TRACK
I
FB(LEAK)
V
FB(CLAMP)
V
SDO(OL)
PARAMETER
Supply Voltage
Supply Current
Supply Undervoltage Lockout
Supply Undervoltage Lockout Hysteresis
ON Pin Threshold Voltage
ON Pin Hysteresis
ON Pin Input Current
RAMP Pin Input Current
RAMPBUF Output Low Voltage
RAMPBUF Output High Voltage,
V
RAMPBUF(OH)
= V
CC
– V
RAMPBUF
Ramp Buffer Offset,
V
OS
= V
RAMPBUF
– V
RAMP
I
FB
to I
TRACK
Current Mismatch
I
ERROR(%)
= (I
FB
– I
TRACK
)/I
TRACK
TRACK Pin Voltage
FB Pin Leakage Current
FB Pin Clamp Voltage
SDO
Output Low Voltage
V
ON
= 1.2V, V
CC
= 5.5V
0V < V
RAMP
< V
CC
, Ramp On
0V < V
RAMP
< V
CC
, Ramp Off
I
RAMPBUF
= 1mA
I
RAMPBUF
= –1mA
V
RAMP
= V
CC
/2, I
RAMPBUF
= 0mA
I
TRACK
= –10μA
I
TRACK
= –1mA
I
TRACK
= –10μA
I
TRACK
= –1mA
V
FB
= 2V, V
CC
= 5.5V
1μA < I
FB
< 1mA
I
SDO
= 1mA, V
CC
= 2.3V
l
l
l
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. 2.9V < V
CC
< 5.5V unless otherwise noted (Note 2).
CONDITIONS
l
MIN
2.9
0.25
3
2.2
1.210
30
–9
9
l
l
l
l
l
l
TYP
0.56
3.6
2.5
25
1.230
75
0
–10
10
20
45
MAX
5.5
1.2
4.2
2.7
1.250
150
±100
–11
11
100
150
30
±5
±5
0.82
0.82
±100
2.3
0.4
UNITS
V
mA
mA
V
mV
V
mV
nA
μA
μA
mV
mV
mV
%
%
V
V
nA
V
V
I
FB
= 0mA, I
TRACK
= 0mA
I
FB
= –1mA, I
TRACK
= –1mA, I
RAMPBUF
= –1mA
V
CC
Rising
V
ON
Rising
–30
0
0
0
0.77
0.77
1.5
0.800
0.800
±1
2
0.1
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:
All currents into the device pins are positive; all currents out of
device pins are negative. All voltages are referenced to ground unless
otherwise specified.
TYPICAL PERFORMANCE CHARACTERISTICS
I
CC
vs V
CC
750
I
TRACK
= I
FB
= 0mA
I
RAMBUF
= 0mA
4.70
I
CC
vs V
CC
I
TRACK
= I
FB
= –1mA
I
RAMBUF
= –2mA
820
V
TRACK
vs Temperature
700
4.65
V
TRACK
(mV)
2.5
3.0
3.5
4.0 4.5
V
CC
(V)
5.0
5.5
6.0
2927 G02
810
600
I
CC
(mA)
I
CC
(μA)
650
4.60
800
4.55
790
550
4.50
780
500
2.5
3.0
3.5
4.0 4.5
V
CC
(V)
5.0
5.5
6.0
2927 G01
4.45
770
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2927 G03
2927fb
3
LTC2927
TYPICAL PERFOR A CE CHARACTERISTICS
V
ON(TH)
vs Temperature
1.240
1.235
24
1.230
V
ON(TH)
(V)
1.225
1.220
1.215
12
1.210
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2927 G04
V
RAMPBUF(OH)
(mV)
V
RAMPBUF(OL)
(mV)
MAX I
TRACK
vs V
CC
60
V
TRACK
= 0V
5
50
I
TRACK
(mA)
40
3
V
SDO(OL)
(V)
ERROR (%)
30
20
10
2.5
3.0
3.5
4.0 4.5
V
CC
(V)
5.0
PIN FUNCTIONS
TSOT/DFN Packages
V
CC
(Pin 1/Pin 8):
Supply Voltage Input. Operating range
is from 2.9V to 5.5V. An undervoltage lockout asserts
SDO
until V
CC
> 2.5V. V
CC
should be bypassed to GND with a
0.1μF capacitor.
SDO
(Pin 2/Pin 7):
Slave Supply Shutdown Output.
SDO
is an open-drain output that holds the shutdown (RUN/SS)
pin of the slave supply low until the V
CC
pin is pulled above
2.5V, and the ON pin is pulled above 1.23V, or RAMP is
above 200mV.
SDO
is pulled low again when both RAMP
< 200mV and ON < 1.23V. If the slave supply is capable
of operating with an input supply that is lower than the
LTC2927’s minimum operating voltage of 2.9V, the
SDO
pin can be used to hold off the slave supply. Tie the
SDO
pin to GND if unused.
FB (Pin 3/Pin 6):
Feedback Control Output. FB pulls up
on the feedback node of the slave supply. Tracking is
achieved by mirroring the current from TRACK into FB.
A resistive divider connecting RAMPBUF and TRACK will
force the output voltage of the slave supply to track RAMP
.
To prevent damage to the slave supply, the FB pin will not
force the slave’s feedback node above 2.3V. In addition,
the LTC2927 will not actively sink current from this node,
even when it is unpowered.
2927fb
4
U W
5.5
V
RAMPBUF(OL)
vs Temperature
28
26
65
22
20
18
16
14
45
10
–50
60
55
50
70
V
RAMPBUF(OH)
vs Temperature
–25
0
25
50
TEMPERATURE (°C)
75
100
2927 G05
40
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2927 G06
Tracking Cell Error vs I
TRACK
ERROR =
4
V
TRACK
I
•
FB
–1
0.8V
I
TRACK
1.0
V
SDO(OL)
vs V
CC
0.8
0.6
I
SDO
= 5mA
0.4
2
1
0.2
I
SDO
= 10μA
0
1
2
3
V
CC
(V)
4
5
2927 G0
6.0
2927 G07
0
1
2
3
I
TRACK
(mA)
4
5
2927 G0
0.0
LTC2927
PI FU CTIO S
TSOT/DFN Packages
GND (Pin 4/Pin 5):
Device Ground.
TRACK (Pin 5/Pin 4):
Tracking Control Input. A resistive
voltage divider between RAMPBUF and TRACK determines
the tracking profile of the slave supply. TRACK servos to
0.8V, and the current supplied at TRACK is mirrored at FB.
The TRACK pin is capable of supplying at least 1mA when
V
CC
= 2.9V. Under short circuit conditions, the TRACK pin
is capable of supplying up to 70mA. Do not connect to
GND for extended periods. Limit the capacitance at the
TRACK pin to less than 25pF
.
RAMPBUF (Pin 6/Pin 3):
Ramp Buffer Output. Provides
a low impedance buffered version of the signal on the
RAMP pin. This buffered output drives the resistive volt-
age divider that connects to the TRACK pin. Limit the
capacitance at the RAMPBUF pin to less than 100pF Float
.
RAMPBUF if unused.
RAMP (Pin 7/Pin 2):
Ramp Buffer Input. The RAMP pin is
the input to the voltage buffer whose output drives a resis-
tive voltage divider connected to the TRACK pin. Connect
this input to a capacitor to set the ramp voltage generated
from internal 10μA pull-up or pull-down currents. RAMP
can also be connected to an external ramping signal for
tracking. Ground RAMP if unused.
ON (Pin 8/Pin 1):
On Control Input. The voltage level of
the ON pin relative to its 1.23V threshold (with 75mV
hysteresis) controls the tracking direction of the LTC2927.
An active high causes a 10μA pull-up current to flow at
the RAMP pin, which charges an external capacitor. An
active low at the ON pin causes a 10μA pull-down cur-
rent at the RAMP pin to discharge the external capacitor
Problem description:When using a power supply, the customer requires the output ripple to be as small as possible, but does not want to use LDO.
Solution:LC filtering can be added at the back end of t...
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Analogue and Mixed Signal
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