FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
SHUTDOWN INPUT (SD)
POWER GOOD OUTPUT SIGNAL (PG)
If this pin is tied to the GND pin, the device will be in
Shutdown Mode. If left unconnected or tied to the VIN pin, the
device will be in Normal Mode. The pin has an internal pull up
of 1.5 MΩ.
This is an active low open drain output that is used to
report the status of the device to a host. This output activates
after a successful power up sequence and stays active as
long as the device is in normal operation and is not
experiencing any faults. This output activates after a 10 ms
delay and must be pulled up by an external resistor to a
supply voltage (e.g., VIN).
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
System Control
& Logic
Internal Bias
Circuits
Oscillator
Control &
Supervisory
Functions
Tracking &
Sequencing
Protection
Functions
Buck Converter
Figure 4. 34713 Block Diagram
down commands. It communicates with the buck converter to
INTERNAL BIAS CIRCUITS
manage the switching operation and protects it against any
faults.
This block contains all circuits that provide the necessary
supply voltages and bias currents for the internal circuitry. It
consists of:
OSCILLATOR
• Internal Voltage Supply Regulator: This regulator
supplies the VDDI voltage that is used to drive the digital/
analog internal circuits. It is equipped with a Power-On-
Reset (POR) circuit that watches for the right regulation
levels. External filtering is needed on the VDDI pin. This
block will turn off during the shutdown mode.
• Internal Bandgap Reference Voltage: This supplies the
reference voltage to some of the internal circuitry.
• Bias Circuit: This block generates the bias currents
necessary to run all of the blocks in the IC.
This block generates the clock cycles necessary to run the
IC digital blocks. It also generates the buck converter
switching frequency. The switching frequency has a default
value of 1.0 MHz and can be programmed by connecting a
resistor divider to the FREQ pin, between VDDI and GND
pins (See Figure 1).
PROTECTION FUNCTIONS
This block contains the following circuits:
• Over Current Limit and Short Circuit Detection: This
block monitors the output of the buck converter for over
current conditions and short circuit events and alerts the
system control for further command.
• Thermal Limit Detection: This block monitors the
temperature of the device for overheating events. If the
temperature rises above the thermal shutdown
SYSTEM CONTROL AND LOGIC
This block is the brain of the IC where the device
processes data and reacts to it. Based on the status of the SD
pin, the system control reacts accordingly and orders the
device into the right status. It also takes inputs from all of the
monitoring/protection circuits and initiates power up or power
34713
Analog Integrated Circuit Device Data
Freescale Semiconductor
10
FREESCALE [ Freescale ]
