DTL4A View Datasheet(PDF) - DATEL Data Acquisition products
Part Name
Description
MFG CO.
'DTL4A' PDF : 5 Pages View PDF
DTL Series
100 WATT, SERIAL-INPUT ELECTRONIC LOADS
Initialization
Preparing the DTL4A 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 significant bit (MSB, bit 1, D11) and ending with the least significant
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 DTL4A’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 final desired value.
Software: C Language
The following steps describe a typical timing sequence when using the
DTL4A’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:
BIT_0 = 1, BIT_1 = 1, BIT_2 = X (don’t care), BIT_3 = 1
2. Bring the Control Strobe low.
BIT_0 = 0
3. Apply the MSB (D11) of the serial data word to Serial Data In.
BIT_2 = 0 or 1
4. Toggle the Clock high-low-high.
BIT_3 = 1 to 0 to 1
5. Apply D10 of the serial data word to Serial Data In.
BIT_2 = 0 or 1
6. Toggle the Clock high-low-high.
BIT_3 = 1 to 0 to 1
7. Repeat the process for remaining data bits D9 through D0.
8. Drive the Control Strobe high.
BIT_0 = 1
9. Toggle the Latch Data input high-low-high.
BIT_1 = 1 to 0 to 1.
Output Compliance Voltage and the Fault Line
For proper operation, the DTL4A’s output/load voltage must
always be between 2.5 and 150 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 150V
can damage the device. Voltages <2.5V will result in insufficient
biasing of the output current source and consequently unpredict-
able 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 DTL4A’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 10kΩ pull-up resistor to +5V).
Under normal conditions, its output is high (logic "1"). Under fault
conditions (VOUT < 2.5V), its output drops to a logic "0." There is
no output/load-voltage monitoring circuit for voltages greater than
150V, and operation above 150V can damage the device.
An "offset supply" can be inserted between the DTL4A’s –Load
output (pins 8 and 9) and the power device under test (DUT)
to "translate" the DTL4A’s 147.5V output/load voltage range. The
offset supply must have adequate current capabilities and be con-
nected with the polarities indicated in Figure 2 below. Under no
circumstances should the voltage across the DTL4A’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 +145 Volts. Such a configuration
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 DTL4A always sees at least 5 Volts across its outputs.
11
+LOAD
10
DTL4A
9
–LOAD
8
5V
–
+
+
DUT
–
SHORT
CIRCUIT
RELAY
Figure 2. An "Offset Supply" Enables
True Short-Circuit Testing
Thermal Considerations
The DTL4A 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 DTL4A applications. Please contact us for details.
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