ISL21400USB-EVALZ Intersil, ISL21400USB-EVALZ Datasheet - Page 14

• Manufacturer Part Number: ISL21400USB-EVALZ
• Description: EVAL BOARD FOR ISL21400
• Manufacturer: Intersil

Specifications of ISL21400USB-EVALZ

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Applications Information
Power-Up Considerations
The ISL21400 has on-chip EEPROM memory storage for
the DAC and gain settings of the device. These settings
must be recalled correctly on power-up for proper operation.
Normally there are no issues with recall, although it is always
best to provide a smooth, glitch-free power-up waveform on
V
help with power-up as well as V
Noise Performance
The output noise voltage in a 0.1Hz to 10Hz bandwidth is
typically 90µV
bandpass filter made of a 1-pole high-pass filter with a
corner frequency at 0.1Hz and a 2-pole low-pass filter with a
corner frequency at 12.6Hz to create a filter with a 9.9Hz
bandwidth. Load capacitance up to 5000pF can be added
but will result in only marginal improvements in output noise
and transient response. The output stage of the ISL21400 is
not designed to drive heavily capacitive loads. For high
impedance loads, an R-C network can be added to filter high
frequency noise and preserve DC control.
Output Voltage Programming Considerations
Setting and controlling the output voltage of the ISL21400
can be done easily by breaking down the components into
temperature variant and invariant, and setting them
separately. Let’s use Equation 1 to derive separate
Reference Output and Output Temperature Slope equations:
The first term controls the output DC value, and the second
term controls the Temperature slope, where
A
A
V
CC
REF
TS
OUT
=
. Adding a small 0.1µF capacitor at the device V
SIGNAL AT SDA
=
⎛
⎝
FROM THE
=
=
(
----------------------------------
SIGNALS
--------- -
255
2 m
MASTER
SIGNALS FROM
⎧
⎨
⎩
n
{
•
Reference Term
A
A
V
255
V
THE SLAVE
(ranges from 0 to 1)
) 255
•
•
P-P
–
V
V
REF
REF
. The noise measurement is made with a
⎞ (ranges from -1 to +1)
⎠
S
T
A
R
T
•
•
--------- -
255
BYTE WITH R/W = 0
0
A
n
IDENTIFICATION
REF
1
⎫
⎬
⎭
0
+
}
+
1
⎧
⎨
⎩
14
+
A
A A A
Temp Slope Term
{
V
OUT
A
•
V
V
•
TS
0
V
load changes.
TS
•
A
C
K
⎛
⎝
FIGURE 18. RANDOM ADDRESS READ SEQUENCE
•
(
----------------------------------
0 0 0
2 m
A
•
TS
ADDRESS
255
}""
BYTE
) 255
0
–
0
CC
⎞
⎠
⎫
⎬
⎭
will
A
C
K
ISL21400
A
R
S
T
T
BYTE WITH R/W = 1
0
IDENTIFICATION
1
0
1
V
DC OUTPUT CONTROL DISCUSSION
The reference term yields Equation 4 for Reference Output:
Note that the DC term is dependent on the 1.20V reference
voltage, which is constant, the overall gain, A
Reference gain, A
from 0 to 4, the total reference DC output can range from
0.0V to 4.8V. In order to get the 4.8V output, V
greater than 4.8V by the output dropout plus any overhead
for output loading (the specification for V
with V
changes with A
(A
A
TEMP SENSE CONTROL DISCUSSION
Equation 4 yields this expression, Equation 5, for
Temperature Slope:
Since V
base temp slope of the device, K (-2.1mV/°C), and the gain
terms A
portion of V
The product A
Slope can range from -8.4 to +8.4mV/°C, which is
independent of the output DC voltage. The resolution of
Slope control is determined by this range (±8.4mV/°C) and
the gain terms, and will vary from 65.8µV/°C/bit (A
down to 16.2µV/°C/bit (A
At T = T
cause a change in V
V
from T = +25°C, V
programmed Temp Slope.
A A A
V
V
V
OUT
OUT
OUT
OUT
V
= 1, the resolution is 4.7mV/bit.
= 4), the resolution is 4.80/255 or 18.8mV/bit. With
(
(
(DC) control. As temperature increases or decreases,
1
(DC)
CC
TS
TS
V
TS
0
A
C
K
)
)
= 5.5V). The Resolution of V
and A
= +25°C, V
=
=
=
= K(T - T
OUT
A
A
A
FIRST READ
DATA BYTE
V
V
V
V
V
*A
TS
•
•
•
, so that with a 4.80V full scale output
at a specific temperature:
K
V
V
TS
. This gives a formula (Equation 6) for the
REF
OUT
REF
TS
•
0
A
ranges from -4 to 4, so the Temperature
OUT
OUT
), the slope term is dependent on the
•
TS
. Since the product A
•
A
will then change according to the
A
TS
•
, and V
V
(TS) = 0, no changes in A
REF
(
A
C
K
= 1).
T T
–
0
OUT
)
A
C
K
will only vary with the
OUT
LAST READ
DATA BYTE
OUT
(DC) control
V
*A
V
= 5.0V is listed
, and the
CC
REF
March 31, 2011
must be
V
TS
ranges
= 4)
FN8091.3
O
(EQ. 4)
(EQ. 5)
(EQ. 6)
S
T
P
will