LTC2920-1/LTC2920-2
4
292012fa
PI FU CTIO S
UUU
V
CC
(Pin 1/Pin 8): Power Supply Input. All internal circuits
are powered from this pin. V
CC
should be connected to a
low noise power supply voltage between 2.3V and 6V and
should be bypassed with at least a 0.1μF capacitor to the
GND pin in close proximity to the LTC2920. Current
sourced out of the I
M
pins comes from the V
CC
pin. Note
that V
CC
must come up no later than the time the
controlled power supply turns on or damage to the load
may result. See Preventing Potential Power Supply Over-
voltages in the Applications Information section for power
sequencing considerations. In certain applications, it may
be necessary to further isolate V
CC
by adding a resistor in
series with its power source. See V
CC
Power Filtering in the
Applications Information section.
GND (Pin 2/Pin 6): Ground. All internal circuits are re-
turned to the GND pin. Connect this ground pin to the
ground of the power supply(s) being margined. Current
sunk into the I
M
pins of the LTC2920 is returned to ground
through this pin.
R
S1
(Pin 4/Pin 4): I
M1
Current Set Input. The R
S1
pin is
used to set the margining current which is sourced out of
or sunk into the I
M1
pin. The R
S1
pin must be connected to
either V
CC
or ground with an external resistor R
SET
with a
value between 6k and 200k. Connecting R
SET
to ground
sets the current at the I
M1
pin with a multiplier of 1.
Connecting R
SET
to V
CC
sets the current at the I
M1
pin with
a multiplier of 30. If R
SET
is connected to ground, ≈1V will
appear at the R
S1
pin. If R
SET
is connected to V
CC
, ≈(V
CC
–
1V) will appear at the R
S1
pin. In either case, the current
through R
SET
will be ≈1V/R
SET
.
(S5 Package/MS8 Package)
I
M1
(Pin 3/Pin 5): I
M1
Current Output. This pin should be
connected to the power supply feedback pin or voltage
adjust pin. (See the Applications Information section for
further details.) Current is either sourced out of or sunk
into this pin. The direction of the current is controlled by
the IN1 pin. The amount of current flowing into or out of
the I
M1
pin is controlled by the R
S1
pin.
IN1 (Pin 5/Pin 3): I
M1
Control Pin. This pin is a 3-level input
pin which controls the I
M1
pin. If the IN1 pin is pulled above
V
IH
, current is sunk into the I
M1
pin. If the IN1 pin is pulled
below V
IL
, current is sourced from the I
M1
pin. If the IN1
pin is left floating, or held between 1.1V and 1.4V, the I
M1
pin is a high impedance output. Internally, the IN1 pin is
connected to a 1.2V voltage source by an internal ~10k
resistor. The LTC2920 has an internal RC circuit to sup-
press noise entering from this pin.
LTC2920-2 Only
R
S2
(NA/Pin 1): I
M2
Current Set Input. Sets the current for
I
M2
. See R
S1
.
I
M2
(NA/Pin 7): I
M2
Current Output. This pin is the second
margin current output for the LTC2920. See I
M1
.
IN2 (NA/Pin 2): I
M2
Control Pin. This pin controls the
current at the I
M2
pin. See IN1.
