DTL-30753 Murata Power Solutions, DTL-30753 Datasheet - Page 4

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DTL-30753

Manufacturer Part Number
DTL-30753
Description
Digital to Analog Converters - DAC Digit Programmable Electronic Load
Manufacturer
Murata Power Solutions
Datasheet

Specifications of DTL-30753

Product Category
Digital to Analog Converters - DAC
Conversion Rate
20 KHz
Resolution
12 bit
Initialization
Preparing the DTL3A to accept new digital data is accomplished by applying
logic "1's" to Control Strobe (CS, pin 7), Latch Data (LD, pin 4) and Clock
(CLK, pin 6) with all signals present and stable for a minimum of 1µsec.
During this interval, it does not matter whether or not data is present on the
Serial Data In (SDI, pin 5) line.
Serial Data
Following initialization, the 12-bit digital word representing the desired output
current is applied to the SDI pin. The serial data should appear starting with
the most signifi cant bit (MSB, bit 1, D11) and ending with the least signifi cant
bit (LSB, bit 12, D0). With each data bit present and stable on the SDI line,
the CLK must be toggled through a low-to-high transition to register that bit.
Twelve rising clock edges, at rates up to 500kHz, are required to clock all 12
digital bits into the DTL3A’s input register.
Latching Data and Presenting It to the D/A
After loading the LSB, the serial data word is latched by bringing the Control
Strobe (pin 7) high and then toggling the Latch Data pin (pin 4) through a
high-low-high sequence. Approximately 100µsec later, the output current will
settle to its fi nal desired value.
Software: C Language
The following steps describe a typical timing sequence when using the
DTL3A’s 4 digital inputs and a programming language such as C. Using 4 bits
of a typical 8-bit port, assign BIT_0 to the Control Strobe (CS, pin 7), BIT_1
to Latch Data (LD, pin 4), BIT_2 to Serial Data In (SDI, pin 5), and BIT_3
to the Clock (CLK, pin 6).
1. Initialize with Control Strobe, Latch Data, and Clock high:
2. Bring the Control Strobe low.
3. Apply the MSB (D11) of the serial data word to Serial Data In.
4. Toggle the Clock high-low-high.
5. Apply D10 of the serial data word to Serial Data In.
6. Toggle the Clock high-low-high.
7. Repeat the process for remaining data bits D9 through D0.
8. Drive the Control Strobe high.
9. Toggle the Latch Data input high-low-high.
DTL Series
BIT_0 = 1, BIT_1 = 1, BIT_2 = X (don’t care), BIT_3 = 1
BIT_0 = 0
BIT_2 = 0 or 1
BIT_3 = 1 to 0 to 1
BIT_2 = 0 or 1
BIT_3 = 1 to 0 to 1
BIT_0 = 1
BIT_1 = 1 to 0 to 1.
1 0 0 W A T T , H I G H - V O L T A G E E L E C T R O N I C L O A D S
4
Output Compliance Voltage and the Fault Line
For proper operation, the DTL3A’s output/load voltage must always be
between 2.5 and 200 Volts. The device cannot be used to directly load low-
voltage, e.g. 1.8V or 2.5V, power components or to simulate a true short
circuit (0 Volts). Voltages greater than 200V can damage the device. Voltages
<2.5V will result in insuffi cient biasing of the output current source and
consequently unpredictable or no operation. Accordingly, we have installed
an internal output/load-voltage monitoring circuit. If the output/load voltage
drops below 2.5V and the DTL3A’s output is at risk of becoming disabled,
the Fault line activates.
The Fault line is an optically isolated, active-low function with an open-
collector output (internal 10k pull-up resistor to +5V). Under normal condi-
tions, its output is high (logic "1"). Under fault conditions (V
output drops to a logic "0." There is no output/load-voltage monitoring circuit
for voltages greater than 200V, and operation above 200V can damage the
device.
An "offset supply" can be inserted between the DTL3A’s –Load output (pins
8 and 9) and the power device under test (DUT) to "translate" the DTL3A’s
197.5V output/load voltage range. The offset supply must have adequate
current capabilities and be connected with the polarities indicated in Figure 2
below. Under no circumstances should the voltage across the DTL3A’s output
be allowed to experience a polarity reversal.
If a 5V/20A offset supply is inserted as shown, the range of DUT voltages
will be –2.5 to +195 Volts. Such a confi guration can be used for true short-
circuit testing. A mechanical relay can be used to short the outputs of the
DUT while the offset supply ensures the DTL3A always sees at least 5 Volts
across its outputs.
Thermal Considerations
The DTL3A can reliably handle 100W loads if its case temperature is
maintained at or below +50°C. With no heat sinking or auxiliary cooling, the
device can only handle loads up to 10 Watts. Please refer to the Temperature
Derating Curve for additional information. DATEL’s Electronic Load Applica-
tions Engineers can assist you in developing heat-sink solutions for your
higher-power DTL3A applications. Please contact us for details.
DTL3A
+LOAD
–LOAD
Figure 2. An "Offset Supply" Enables
11
10
9
8
True Short-Circuit Testing
5V
+
DUT
+
OUT
< 2.5V), its
CIRCUIT
SHORT
RELAY

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