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7

IRDCiP2001-A

Sequencing Tip

It’s important to have proper sequencing between the control IC and the iP2001 blocks. This assures the soft-start

routine of the IC will properly ramp-up the output voltage during a power-up or restart from shut down event. Figure

7 shows a simple and cost effective way to synchronize the iP2001 blocks with an HIP6311 control IC in a 2 Phase

configuration.

Placing Schottky diodes between the iP2001’s PRDY pin and the IC’s FS/DIS pin creates an interface analogous to an

AND operation. With this configuration, no single iP2001 can enable the IC independently. This configuration also

resolves any differences in timing and logic thresholds between iP2001 devices. The capacitors are used to filter

high frequency noise on the PRDY line. Additionally, the ENABLE pin of the iP2001 blocks can be used as the master

control switch for the system.

During power-up, the PRDY pin is held low until V

forward biased and clamps the FS/DIS pin well below the disable voltage of the HIP6311 IC (typically 1V). Upon

reaching 4.4V, the PRDY pin transitions to a logic-level high state and releases the clamp on the FS/DIS pin. This

enables the IC and allows its soft start routine to begin (see figure 8), assuming the voltage at the IC’s V

greater than its power-on reset threshold.

When the ENABLE pin is held to a logic-level low state (shut down mode), the PRDY pin clamps the FS/DIS pin of the

IC below the disable voltage. After the ENABLE pin transitions to a logic-level high state, the PRDY releases the

clamp on the FS/DIS pin, enabling the IC and allowing its soft start routine to begin (see figure 9).

During power-down, the PRDY pin transitions to a logic-level low state when the V

out threshold of the iP2001 blocks. The FS/DIS pin is then clamped below the disable voltage, disabling the control IC.

Fig. 7 - Sequencing Schematic

51k

VSEN

GND

FS/DIS

FB

COMP

PWM3

ISEN3

ISEN2

PWM2

PWM1

HIP6311

BAT54

BAT54

ENABLE

PRDY1

ENABLE

iP2001

iP2001

PRDY2

Master

Control

0.22µF

0.22µF