LTC2927 Linear Technology, LTC2927 Datasheet - Page 4

• Manufacturer Part Number: LTC2927
• Description: Single Power Supply Tracking Controller
• Manufacturer: Linear Technology

LTC2927
TYPICAL PERFOR A CE CHARACTERISTICS
PIN FUNCTIONS
V
is from 2.9V to 5.5V. An undervoltage lockout asserts SDO
until V
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
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
4
CC
1.240
1.220
1.215
1.210
1.235
1.230
1.225
60
20
10
(Pin 1/Pin 8): Supply Voltage Input. Operating range
50
40
30
–50
2.5
V
CC
MAX I
V
ON(TH)
TRACK
> 2.5V. V
3.0
–25
TRACK
= 0V
vs Temperature
3.5
TEMPERATURE (°C)
0
vs V
CC
4.0
V
CC
CC
25
should be bypassed to GND with a
(V)
4.5
50
TSOT/DFN Packages
5.0
W
75
5.5
U
2927 G04
2927 G07
100
6.0
CC
pin is pulled above
28
26
24
22
20
18
16
14
12
10
5
1
0
4
3
2
–50
V
Tracking Cell Error vs I
1
ERROR =
RAMPBUF(OL)
–25
V
2
TRACK
0.8V
TEMPERATURE (°C)
0
I
TRACK
vs Temperature
•
I
TRACK
25
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.
I
3
FB
(mA)
–1
50
TRACK
4
75
2927 G0
2927 G05
100
5
1.0
0.8
0.6
0.4
0.2
0.0
70
65
60
55
50
45
40
–50
V
V
0
RAMPBUF(OH)
SDO(OL)
–25
1
www.DataSheet4U.com
vs V
I
TEMPERATURE (°C)
SDO
0
2
CC
= 10μA
I
vs Temperature
SDO
V
CC
25
= 5mA
(V)
3
50
4
75
5
2927 G0
2927fb
2927 G06
100