ltc2752lx Linear Technology Corporation, ltc2752lx Datasheet - Page 9

• Manufacturer Part Number: ltc2752lx
• Description: Ltc2752 Dual16-bit Softspan Iout Dacs Features
• Manufacturer: Linear Technology Corporation

pin FuncTions
REFA (Pins 1, 2): Feedback Resistor for the DAC A Refer-
ence Inverting Amplifier, and Reference Input for DAC A.
The 20k feedback resistor is connected internally from
REFA to R
output of the DAC A reference inverting amplifier (see
Typical Applications). Typically –5V; accepts up to ±15V.
Pins 1 and 2 are internally shorted together.
R
erence Amplifier Inverting Resistors. The 20k reference
inverting resistors are connected internally from R
R
Diagram). For normal operation tie R
input of the external reference inverting amplifier (see
Typical Applications).
GE
pin can be used to null gain error or to compensate for
reference errors. The gain change expressed in LSB is
the same for any output range. See System Offset and
Gain Adjustments in the Operation section. Tie to ground
if not used.
R
Inverting Amplifier. The 20k input resistor is connected
internally from R
R
Applications). Either or both of these precision-matched
resistor sets (each set comprising R
may be used to invert positive references to provide the
negative voltages needed by the DACs. Typically 5V; accepts
up to ±15V. Pins 5 and 6 are internally shorted together.
GND (Pins 7, 10, 15, 17, 18, 27, 30): Ground; tie to
ground.
I
Complement Sense and Force Pins. Tie to ground via a
clean, low-impedance path. These pins may be used with
a precision ground buffer amp as a Kelvin sensing pair
(see the Typical Applications section).
CS/LD (Pin 11): Synchronous Chip Select and Load Input
Pin.
SDI (Pin 12): Serial Data Input. Data is clocked in on the
rising edge of the serial clock (SCK) when CS/LD is low.
SCK (Pin 13): Serial Clock Input.
OUT2AS
COMA
COMA
INA
INA
ADJA
to the external positive reference voltage (see Typical
(Pins 5, 6): Input Resistor for External Reference
and from R
(Pin 3): Virtual Ground Point for the DAC A Ref-
, I
(Pin 4): Gain Adjust Pin for DAC A. This control
COMA
OUT2AF
. For normal operation tie this pin to the
INA
(Pins 8, 9): DAC A Current Output
COMA
to R
to REFA, respectively (see Block
COMA
. For normal operation tie
INX
COMA
, R
COMX
to the negative
and R
INA
EFX
to
)
SRO (Pin 14): Serial Readback Output. Data is clocked out
on the falling edge of SCK. Readback data begins clocking
out after the last address bit A0 is clocked in. SRO is an
active output only when the chip is selected (i.e., when
CS/LD is low). Otherwise SRO presents a high impedance
output in order to allow other parts to control the bus.
V
pass with a 0.1μF low ESR ceramic capacitor to ground.
CLR (Pin 19): Asynchronous Clear Input. When this pin is
low, all DAC registers (both code and span) are cleared to
zero. All DAC outputs are cleared to zero volts.
RFLAG (Pin 20): Reset Flag Output. An active low output
is asserted when there is a power-on reset or a clear event.
Returns high when an Update command is executed.
DNC (Pin 21): Do not connect this pin.
M-SPAN (Pin 22): Manual Span Control Pin. M-SPAN is
used in conjunction with pins S2, S1 and S0 (Pins 25, 24
and 23) to configure all DACs for operation in a single,
fixed output range.
To configure the part for manual span use, tie M-SPAN
directly to V
hardware pin strapping of pins S2, S1 and S0 (rather than
through the SPI port); and Write and Update commands
have no effect on the active output span.
To configure the part for SoftSpan use, tie M-SPAN directly
to GND. The output ranges are then individually control-
lable through the SPI port; and pins S2, S1 and S0 have
no effect.
See Manual Span Configuration in the Operation section.
M-SPAN must be connected either directly to GND (SoftSpan
configuration) or to V
S0 (Pin 23): Span Bit 0 Input. In Manual Span mode
(M-SPAN tied to V
to select a single fixed output range for all DACs. These
pins should be tied to either GND or V
unused.
S1 (Pin 24): Span Bit 1 Input. In Manual Span mode (M-SPAN
tied to V
a single fixed output range for all DACs. These pins should
be tied to either GND or V
DD
(Pin 16): Positive Supply Input; 2.7V ≤ V
DD
), pins S0, S1 and S2 are pin-strapped to select
DD
. The DAC output range is then set via
DD
), pins S0, S1 and S2 are pin-strapped
DD
(manual span configuration).
DD
even if they are unused.
DD
LTC2752
even if they are
DD
≤ 5.5V. By-

2752f