MC33565 Motorola, MC33565 Datasheet - Page 4

• Manufacturer Part Number: MC33565
• Description: 200 mA INTELLIGENT LDO REGULATOR WITH SMART BYPASS CONTROL
• Manufacturer: Motorola

LDO regulator ensures that no significant reverse current will
flow from +3.3 V out back to the +5 V in input when the 5V input
is not powered and the 3.3 V in supply is present.
the 5V input supply. When the 5V supply drops below a given
threshold, the +3.3 V in bypass transistor (an external
P–channel MOSFET) is enabled. The 5V detect logic is
active throughout the entire range of ramp–up from 0 to 5.5V.
Additionally, the Drive out signal is never turned ON or OFF
inappropriately during ramp–up of the +5 V in supply. Also,
+3.3 V out never drops below 3.0V while +5 V in is above the
5V detect minimum threshold.
circuitry and Drive out control circuitry guarantees that the
4
Input Blocking – The internal NPN pass transistor of the
5 Volt Detect – Internal circuitry detects the presence of
Glitch–free Transfer – The design of the 5V detect
Motherboard/
Mainboard
PCI Slot
+5 Vin
+3.3 Vin
LDO
3.3V aux
5V
Detect
Ref &
Figure 2. Application Block Diagram
Figure 1. Functional Block Diagram
FUNCTIONAL DESCRIPTION
+3.3 Vin
Compensation
+5 Vin
V ref
Hysteresis
Gnd
N/C
&
1
2
3
4
MC33565
5V detect
MC33565
+3.3 V out will not exceed the output voltage specification
listed in the table of DC Operating Specifications even with
+5 V in ramping up and down at the extremes of the slew rates
in the table of AC Operating Specifications (provided the
device is used with an MGSF1P02ELT PMOS FET on Drive
out along with a minimum 4.7 F capacitor on the +3.3 V out ).
when external offsets are present on the +5 V in and +3.3 V in
power inputs, the device has been designed to be capable of
operating with either one or both of these inputs rising from or
falling to zero volts, or with offsets of 0.05V to 0.9V as the
inputs ramp up and down.
8
7
6
5
Comp
Driver
Offset Voltage Performance – To ensure performance
+3.3 Vout
Sense in
N/C
Hyst sw
Drive out
Drive out
+3.3 Vout
Sense in
MOTOROLA ANALOG IC DEVICE DATA
4.7 F
External
P–channel
MOSFET
+3.3 Vout
External
4.7 F
cap
PCI NIC/Card
Circuitry