Topology And Circuit Description; Connectors - Analog Devices ADP1046A User Manual

ADP1046A 100Watt
Evaluation board

TOPOLOGY AND CIRCUIT DESCRIPTION

This evaluation board features the ADP1046A in a DC/DC switching power supply in full bridge topology with synchronous
rectification. Figure 1 shows a block diagram of the main components on the board. The circuit is designed to provide a rated
load of 12V/8A from an input voltage source of 36 to 60VDC. The ADP1046A provides functions such as output voltage
regulation, over current protection, load current sharing with multiple power supplies over the share bus, over temperature
protection, and power supply shutdown.
Please refer to the appendix for the detailed schematic. The primary side consists of the input terminals, full bridge switches
(QA to QD), the current sense transformer (T3) and the main transformer (T2). The ADP1046A (U1, on daughter card) resides
on the secondary side and is powered via the USB 5V via an ADP3303 LDO (U2, on daughter card) present on the same
daughter card. The gate signal for the primary switches comes from the ADP1046A through the iCouplers ADuM5230 (U14,
U15) that provide isolation and power. The output of the iCoupler is connected to a buffer as it can source only 10mA of
current. This buffer (network consisting of Q5 and Q6, Q7 and Q8, Q9 and Q10, Q11 and Q12) is used to drive the full bridge
switches.
The secondary side power stage consists of the synchronous rectifiers (Q2 and Q3) and their respective drivers ADP3624
(U1), output inductor (L1), output capacitor (C4, C7), sense resistor (R17), and OrFET (Q1). Diode (D2) and capacitor (C6)
form a peak detector that drives the OrFET along with the charge pump circuit. Capacitors (C23, C64, C67) provide high
frequency decoupling to lower EMI.
Resistor (R10) converts the current into a voltage. The CS1 fast over current flag is comparator based and trips at 1.2V.
Thermistor (RT1) is placed close to the OrFET on the board allowing over temperature protection functionality to be
implemented.
Also present on the secondary is the current sharing circuitry, flag LEDs (D11-D12), and communications port to the software
through the I2C bus.

CONNECTORS

The connections to the evaluation board are shown below.
There is a 4 pin connector for I2C communication. This allows the software to communicate with the evaluation board through
the USB port of the PC. Instead of using an auxiliary supply, the board uses the 5V input from the USB port, and generates
3.3V using an LDO for the ADP1046A. The synchronous rectifier drivers (ADP3624) are also powered by the 5V USB, but are
powered from the main 12V output after the output is in regulation.
Connectors (J8 and J9) are identical and are connected in parallel to each other to allow multiple boards to be connected to
the same I2C bus in a daisy chain configuration. Each board consumes between 150mA and 250mA depending on the
conditions. Particular care must be taken to not overload the USB 5V rail. Some USB ports, especially those connected at a
hub may shut down if overloaded and cause communication problems. In such cases an external 5V power supply is
recommended to power the board between test point TP44(+) and TP21(-).
Connector Evaluation Board Function
J3
J2 Ground Return for 48V DC Input
J4 12V DC Voltage Output
J5 Ground Return for 12V DC Voltage Output
J8, J9
J10
J1
Table 2 - Evaluation board connectors
Rev. 1.3 | Page 4 of 55
48V DC Input
I2C Connector
Share Bus
Daughter card
PRD1386