Delta-electronics DNM User Manual download pdf (Page 11)

8.2.6 Voltage Tracking

The DNM/DNL family was designed for applications that have output voltage tracking

requirements during power-up and power-down. The devices have a TRACK pin to implement

three types of tracking method: sequential, ratio-metric and simultaneous. TRACK simplifies

the task of supply voltage tracking in a power system by enabling modules to track each

other, or any external voltage, during power-up and power-down.

By connecting multiple modules together, customers can get multiple modules to track their

output voltages to the voltage applied on the TRACK pin.

Detailed Description

Sequential Implementation

Sequential start-up is implemented by connecting the power good signal (PWRGD pin) of PS1

to the TRACK pin of PS2 with a resistor–capacitor (RC) circuit. The power up and down that

waveforms in Figures 4 and 5. In Figure 4, the 5V PS1 supply ramps up first. When supply

reaches its final 5V steady state value, the open collector output of the PWRGD pin releases

to the TRACK pin and the PS2 output voltage rises at the rate of the RC time constant. In

Figure 5, the PWRGD pin pull low by PS1 ENABLE off or the PS1 output voltage is below 90%

of the desired regulated voltage. The TRACK pin is pulled low and the PS2 power down.

Figure 3 shows the circuit diagram of sequential start-up when Vo

PS2

tracks the PWRGD of

PS1.

TRACK

PS1

PS2

PS1

Vin

PWRGD

ENABLE

Figure 3. PS1 and PS2 track output voltage Sequential start-up

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Delta-electronics DNM User Manual Page 11