LTC1703CG#TRPBF Linear Technology, LTC1703CG#TRPBF Datasheet - Page 8

• Manufacturer Part Number: LTC1703CG#TRPBF
• Description: IC REG SW DUAL SYNC VID 28SSOP
• Manufacturer: Linear Technology

Specifications of LTC1703CG#TRPBF

• Applications: Controller, Mobile Intel Pentium® III
• Voltage - Input: 3 ~ 7 V
• Number Of Outputs: 2
• Voltage - Output: 0.9 ~ 2 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
* 01111 and 11111 are defined by Intel to signify “no CPU.” The LTC1703
regulated output voltages as low as 800mV without exter-
nal level shifting amplifiers.
The LTC1703’s synchronous switching logic transitions
automatically into Burst Mode operation, maximizing effi-
ciency with light loads. An onboard overvoltage (OV) fault
flag indicates when an OV fault has occurred. The OV flag
can be set to latch the device off when an OV fault has
occurred, or to automatically resume operation when the
fault is removed.
2-Step Conversion
“2-step” architectures use a primary regulator to convert
the input power source (batteries or AC line voltage) to an
intermediate supply voltage, often 5V. This intermediate
voltage is then converted to the low voltage, high current
supplies required by the system using a secondary regu-
lator— the LTC1703. 2-step conversion eliminates the
need for a single converter that converts a high input
voltage to a very low output voltage, often an awkward
design challenge. It also fits naturally into systems that
continue to use the 5V supply to power portions of their
circuitry, or have excess 5V capacity available as newer
LTC1703
Table 1. VID Inputs and Corresponding Output Voltage for
Channel 1
CODE
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111*
8
will generate the output voltages shown when these codes are selected.
VID4
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
VID3
GND
GND
GND
GND
GND
GND
GND
GND
Float
Float
Float
Float
Float
Float
Float
Float
U
VID2
Float
Float
Float
Float
Float
Float
Float
Float
GND
GND
GND
GND
GND
GND
GND
GND
U
VID1
Float
Float
Float
Float
GND
GND
Float
GND
GND
Float
GND
GND
Float
GND
GND
Float
W
VID0
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
U
V
2.00V
1.95V
1.90V
1.85V
1.80V
1.75V
1.70V
1.65V
1.60V
1.55V
1.50V
1.45V
1.40V
1.35V
1.30V
1.25V
OUT1
CODE
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111*
circuit designs shift the current load to lower voltage
supplies.
Each regulator in a typical 2-step system maintains a
relatively low step-down ratio (5:1 or less), running at high
efficiency while maintaining a reasonable duty cycle. In
contrast, a regulator taking a single step from a high input
voltage to a 1.xV output must run at a very narrow duty
cycle, mandating trade-offs in external component values
while compromising efficiency and transient response.
The efficiency loss can exceed that of using a 2-step
solution (see the 2-Step Efficiency Calculation section and
Figure 10). Further complicating the calculation is the fact
that many systems draw a significant fraction of their total
power off the intermediate 5V supply, bypassing the low
voltage supply. 2-step solutions using the LTC1703 usu-
ally match or exceed the total system efficiency of single-
step solutions, and provide the additional benefits of
improved transient response, reduced PCB area and sim-
plified power trace routing.
2-step regulation can buy advantages in thermal manage-
ment as well. Power dissipation in the LTC1703 portion of
a 2-step circuit is lower than it would be in a typical 1-step
VID4
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
VID3
GND
GND
GND
GND
GND
GND
GND
GND
Float
Float
Float
Float
Float
Float
Float
Float
VID2
GND
GND
GND
GND
Float
Float
Float
Float
GND
GND
GND
GND
Float
Float
Float
Float
VID1
Float
Float
Float
Float
Float
Float
Float
Float
GND
GND
GND
GND
GND
GND
GND
GND
VID0
Float
Float
Float
Float
Float
Float
Float
Float
GND
GND
GND
GND
GND
GND
GND
GND
1.275V
1.250V
1.225V
1.200V
1.175V
1.150V
1.125V
1.100V
1.075V
1.050V
1.025V
1.000V
0.975V
0.950V
0.925V
0.900V
V
OUT1
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