FUNCTIONAL DESCRIPTION
FUNCTIONAL TERMINAL DESCRIPTION
operation will be suppressed during startup and shutdown to
ensure that VCORE - VI/O = 0.9 V.
SUPERVISORY FUNCTIONS
Supervisory Circuitry
VB Charge Pump
The supervisory circuitry provides control of the RST line,
an open drain signal, based on system operating conditions
monitored by the 34710. VI/O, VCORE, VB+, and thermal
The high-side MOSFET in the switching regulator (buck
converter) requires a gate drive supply voltage that is biased
higher than the B+ voltage, and this boosted voltage is
provided by the internal charge pump and stored in a
capacitor between the VB pin and the B+ pin. The charge
pump operates directly from the B+ supply, and uses an
shutdown (TSD) detectors in various parts of the chip are
monitored for error conditions. VI/O, VCORE, VB+, and thermal
shutdown have both positive- and negative-going thresholds
for triggering the reset function.
internal oscillator operating at 200 kHz.
The supervisor circuitry also ensures that the regulator
outputs follow a predetermined power-up and power-down
sequence. Specifically, the sequencing ensures that VI/O is
Internal Oscillator
The internal oscillator provides a 200 kHz square wave
signal for charge pump operation and for the buck converter.
never less than 0.9 V below VCORE. This means that VCORE
I/O will be clamped at 0.5 V, and that the VCORE regulator
-
V
34710
Analog Integrated Circuit Device Data
Freescale Semiconductor
10
FREESCALE [ Freescale ]
