IR3865MTRPBF International Rectifier, IR3865MTRPBF Datasheet - Page 12

• Manufacturer Part Number: IR3865MTRPBF
• Description: IC BUCK SYNC ADJ 10A PQFN
• Manufacturer: International Rectifier
• Series: SupIRBuck™r
• Type: Step-Down (Buck), PWMr

Specifications of IR3865MTRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.5 V ~ 12 V
• Current - Output: 10A
• Frequency - Switching: Up to 750kHz
• Voltage - Input: 3 V ~ 21 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: *
• Package / Case: *
• Primary Input Voltage: 21V
• No. Of Outputs: 1
• Output Voltage: 12V
• Output Current: 10A
• No. Of Pins: 17
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 3 - 168 Hours
• Rohs Compliant: Yes
• Leaded Process Compatible: Yes
• Part Status: Preferred
• Package: PQFN / 4 x 5
• Circuit: Single Output
• Iout (a): 10
• Switch Freq (khz): 0 - 750
• Input Range (v): 3.0 - 21
• Output Range (v): 0.5 - 12
• Ocp Otp Uvlo Pre-bias Soft Start And: Constant On-Time + PGOOD + EN + Temp Comp OCP
• Digital Home Media: Yes
• Mobile Computing: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

CIRCUIT DESCRIPTION
UNDER/OVER VOLTAGE MONITOR
The IR3865 monitors the voltage at the FB node
through a 350ns filter. If the FB voltage is below
the under voltage threshold, UV# is set to LOW
holding PGOOD to be LOW. If the FB voltage is
above the over voltage threshold, OV# is set to
LOW, the shutdown signal (SD) is set to HIGH,
MOSFET gates are turned off, and PGOOD
signal is pulled low. Toggling VCC or EN will
allow the next start up. Figure 21 and 22 show
PGOOD
detected. The over voltage and under voltage
thresholds can be found in the Electrical
Specification section.
2/16/2011 Rev2.3
Figure 21. Under/Over Voltage Monitor
Figure 22. Over Voltage Protection
status
change
* typical filter delay
* typical filter delay
when
UV/OV
is
OVER CURRENT MONITOR
The over current circuitry monitors the output
current during each switching cycle. The voltage
across
monitored for over current and zero crossing. The
minimum lower gate interval allows time to
sample VPHASE.
The over current trip point is programmed with a
resistor from the ISET pin to PHASE pin, as
shown in equation 4.
detected, the MOSFET gates are tri-state and SS
voltage is pulled to 0V. This initiates a new soft
start cycle. If there is a total of four OC events, the
IR3865 will disable switching. Toggling VCC or
EN will allow the next start up.
UNDER VOLTAGE LOCK-OUT
The IR3865 has VCC and EN under voltage lock-
out (UVLO) protection. When either VCC or EN is
below their UVLO threshold, IR3865 is disabled.
IR3865 will restart when both VCC and EN are
above their UVLO thresholds.
OVER TEMPERATURE PROTECTION
When the IR3865 exceeds its over temperature
threshold, the MOSFET gates are tri-state and
PGOOD is pulled low. Switching resumes once
temperature drops below the over temperature
hysteresis level.
Figure 23. Over Current Protection
the
R
lower
SET

R
MOSFET,
DSON
19
When over current is
IR3865MBF


I
A
OC
(4)
VPHASE,
12
is