KIT33701DWBEVB Freescale Semiconductor, KIT33701DWBEVB Datasheet - Page 19

• Manufacturer Part Number: KIT33701DWBEVB
• Description: KIT FOR 33701 POWER SUPPLY
• Manufacturer: Freescale Semiconductor
• Type: LDO Controllers & Regulatorsr

Specifications of KIT33701DWBEVB

• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 2, Non-Isolated
• Voltage - Input: 2.8 ~ 6V
• Regulator Topology: Buck
• Frequency - Switching: 300kHz
• Board Type: Fully Populated
• Utilized Ic / Part: MC34701
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Output: -
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: 34701

SWITCHING REGULATOR
default, adjustable in the range from 200kHz to 400kHz),
synchronous buck converter driving integrated high side and
low side N-channel power MOSFETs. The switching
regulator output voltage is adjustable by means of an external
resistor divider to provide the required output voltage within
±2.0% accuracy, and is intended to directly power the core of
the microprocessor. The buck controller uses a PWM voltage
mode control topology with feed-forward to achieve excellent
line and load regulation.
which is used to properly bias the switcher’s MOSFET. In
addition, the boost structure has a very low start-up voltage
(Typically 1.6V), hence ensuring very low input voltage
functionality. A typical bootstrap technique is used to provide
voltage necessary to properly enhance the high side
MOSFET gate. When the regulator is supplied only from low
input voltage (e.g., single +3.3V supply rail), the bootstrap
capacitor is charged from the internal boost regulator output
V
the 34701 to operate from very low input voltage and also
comply with the power sequencing requirements of the
supplied microcontroller.
Analog Integrated Circuit Device Data
Freescale Semiconductor
BST
0 V
The switching regulator is a high frequency (300kHz
The 34702 integrated boost regulator provides a 7.75V rail
Figure 12. Boost Regulator Startup (Not To Scale)
through an external diode. This arrangement allows
0.1 A typ.
6.0 V
I pk = 1 A typ.
0.6 A typ.
0.2 A typ.
7.75V
Booster Inductor Current
Booster Output Voltage
regulator has a current limit with retry capability. When an
over-current condition occurs and the switch current reaches
the peak current limit value, the main (high side) switch is
turned off until the inductor current decays to the valley value,
which is one half of the peak current limit. If an over-current
condition exists for 10ms, the buck regulator control circuit
shuts the switcher OFF and the switcher retry timer starts to
time out. When the timer expires after 100ms, the switcher
engages the start-up sequence and runs for 10ms,
repeatedly checking for the over-current condition.
describes the switching regulator over-current condition and
current limit. During the current limited operation (e.g., in
case of short-circuit on the switching regulator output), the
switching regulator operation is not synchronized to the
oscillator frequency.
depicts the current limit with a retry capability feature of the
switcher (respectively LDO).
Figure 14. Switching Converter Over-current Protection
0 A
To avoid destruction of the supplied circuits, the switching
Figure 13. Switching Regulator Current Limit
Fault Timer
t FAULT = 10 ms
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
I pk
0.5 I pk
Cu rrent Limit
Figure 14
(Not To Scale)
Retry Timer
t Ret = 10 0 ms
(respectively
FUNCTIONAL DESCRIPTION
Figure
t FAULT = 10 ms
Figure 13
15)
34701
I p k
0.5 I pk
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