ltc3770 Linear Technology Corporation, ltc3770 Datasheet - Page 7

• Manufacturer Part Number: ltc3770
• Description: Fast No Rsense Step-down Synchronous Controller With Margining, Tracking And Pll
• Manufacturer: Linear Technology Corporation

V
voltage at this pin is ten times the nominal sense voltage
at maximum output current and can be set from 0.5V to 2V
by a resistive divider from INTV
voltage defaults to 50mV when this pin is tied to ground,
200mV when tied to INTV
between 0.5V to ground or 2V to INTV
V
connects the error amplifier input to an external resistive
divider from V
I
Amplifier Compensation Point. The current comparator
threshold increases with this control voltage. The voltage
ranges from 0V to 2.4V with 0.75V corresponding to zero
sense voltage (zero current).
SGND (Pin 4/Pin 7): Signal Ground. All small-signal
components and compensation components should con-
nect to this ground, which in turn connects to PGND at one
point.
MARGIN1 (Pin 5/Pin 8): The MSB Logic Input for the
Margining Function. Together with the MARGIN0 pin
determines whether the IC is in margin high, margin low,
or no margin state. This pin has a 50k internal pull-down
resistor.
TYPICAL PERFOR A CE CHARACTERISTICS
PI FU CTIO S
TH
RNG
FB
U
(Pin 3/Pin 6): Current Control Threshold and Error
(Pin 2/Pin 5): Error Amplifier Feedback Input. This pin
(Pin 1/Pin 4): Sense Voltage Range Input. The
U
OUT
.
160
140
120
100
U
80
60
40
20
0
Current Limit Foldback
0
V
RNG
(UH Package/G Package)
0.1
= 1V
W
CC
. Do not set this voltage
0.2
CC
U
. The nominal sense
V
FB
0.3
(V)
CC
.
0.4
0.5
3770 G21
0.6
MARGIN0 (Pin 6/Pin 9): The LSB Logic Input for the
Margining Function. Together with the MARGIN1 pin
determines whether the IC is in margin high, margin low,
or no margin state. This pin has a 50k internal pull-down
resistor.
I
from this pin to ground to set the one-shot timer current
and thereby set the switching frequency.
V
The voltage at this pin must be greater than 0.5V and less
than 1V.
V
Output. The maximum current sinking limit is 50µA at
this pin. Do not put a filter capacitor larger than 100pF on
this pin.
MPGM (Pin 10/Pin 13): Programmable Margining Input.
A resistor from this pin to ground sets the margining
current. This current, together with the resistor between
the V
voltage offset.
TRACK/SS (Pin 11/Pin 14): Output Voltage Tracking and
Soft Start Input. When the IC is configured to be the master
of two outputs, a capacitor to ground at this pin sets the
ramp rate for the output voltage. When the IC is configured
ON
REFIN
REFOUT
(Pin 7/Pin 10): On-Time Current Input. Tie a resistor
140
120
100
REFOUT
80
60
40
20
0
(Pin 8/Pin 11): Error Amplifier Reference Input.
Ion Current vs V
0
(Pin 9/Pin 12): Buffered Internal 0.6V Reference
R
ON
= 82k
5
and V
10
INPUT VOLTAGE (V)
REFIN
15
IN
20
pins, determines the margining
25
30
3770 G22
35
LTC3770
3770fb
7