EDGE6420 Datasheet, PDF (7/29 Pages) Semtech Corporation – Per-Pin Electronics Companion DAC

Edge6420
HIGH-PERFORMANCE PRODUCTS – ATE
Circuit Description (continued)
DAC Voltage Output Overview
Minimum / Maximum Output Voltages
The output voltage of Group A, B, C, and D DACs is See Table 2 for the minimum and maximum possible
governed by the following equation:
voltages of a voltage output.
VOUT_[A:D] = KG[A:D] * VREF *
R_GAIN_[A:D]
R_MASTER ^*
DATA
8192
+ VOFFSET_[A:D]
Equation 1.
where:
DATA corresponds to the base-10 value of the binary data
loaded into the shift register shown in Figure 2.
DAC Setting
MSB ... LSB
0000H
1FFFH
V_{OUT_[A:D]} (V)
V_{OFFSET_[A:D]}
V_{MAX_[A:D]}
K_G[A:D] is a multiplying factor that is fixed, as follows:
K_GA = 4
K_GC = 8
K_GB = 4
K_GD = 4
Table 2. Minimum/Maximum Output Voltages
where:
V_REF = 2.5V
V_OFFSET[A:D] is defined in equation 2
Offset
and
The offset for each of the voltage DACs is governed by the
following equation:
VMAX_[A:D]
=
KG[A:D] * VREF *
R_GAIN_[A:D]
R_MASTER
* ⁸¹⁹¹
8192
+ VOFFSET_[A:D]
VOFFSET_[A:D] ₌ KOFFSET * VREF *
0.5 – ^{R_OFFSET_[A:D]}
R_MASTER
where:
Equation 2.
Equation 3.
The most negative voltage possible for the Edge6420 is
–3.5V when VEE = –4.5V.
K_OFFSET = 2
Resolution
V_REF = 2.5V
The resolution of the DACs in Groups A, B, C, and D is:
External Resistors
The recommended resistor values for the above equations
are as follows:
V_{RANGE_[A:D]} / 2¹³
where V_{RANGE_[A:D]} is defined in Equation 4.
Range
R_MASTER = 100KΩ (0.1% precision)
The range of the DACs in Groups A, B, C and D is:
R_GAIN_[A:D] = (0.4 to 1.15) * R_MASTER
R_OFFSET_[A:D] = (0.0 to 1.2) * R_MASTER
VRANGE_[A:D]
=
KG[A:D] _* VREF _*
R_GAIN_[A:D]
R_MASTER
*
8191
8192
Equation 4.
 2000 Semtech Corp.
7
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