SI9119DB Vishay, SI9119DB Datasheet - Page 6

• Manufacturer Part Number: SI9119DB
• Description: Pulse Width Modulation (PWM) Controller IC
• Manufacturer: Vishay

Specifications of SI9119DB

• Silicon Manufacturer: Vishay
• Application Sub Type: Switch Mode
• Kit Application Type: Power Management
• Silicon Core Number: SI9119
• Kit Contents: Board
• Input Voltage Primary Min: 10V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Si9120
Vishay Siliconix
DETAILED DESCRIPTION (CONT’D)
Reference Section
The reference section of the Si9120 consists of a temperature
compensated buried zener and trimmable divider network.
The output of the reference section is connected internally to
the non-inverting input of the error amplifier. Nominal reference
output voltage is 4 V. The trimming procedure that is used on
the Si9120 brings the output of the error amplifier (which is
configured for unity gain during trimming) to within "2% of 4 V.
This compensates for input offset voltage in the error amplifier.
The output impedance of the reference section has been
purposely made high so that a low impedance external voltage
source can be used to override the internal voltage source, if
desired, without otherwise altering the performance of the
device.
Error Amplifier
Closed-loop regulation is provided by the error amplifier, which
is intended for use with “around-the-amplifier” compensation.
A MOS differential input stage provides for high input
impedance. The noninverting input to the error amplifier
(V
supply and should be bypassed with a small capacitor to
ground.
Oscillator Section
The oscillator consists of a ring of CMOS inverters, capacitors,
and a capacitor discharge switch. Frequency is set by an
external resistor between the OSC IN and OSC OUT pins.
(See Typical Characteristics for details of resistor value vs.
frequency.) The DISCHARGE pin should be tied to −V
normal internal oscillator operation. A frequency divider in the
logic section limits switch duty cycle to v 50% by locking the
switching frequency to one half of the oscillator frequency.
Vishay Siliconix maintains worldwide manufacturing capability. Products may be manufactured at one of several qualified locations. Reliability data for Silicon Technology and
Package Reliability represent a composite of all qualified locations.
http://www.vishay.com/ppg?70006.
www.vishay.com
6
REF
) is internally connected to the output of the reference
For related documents such as package/tape drawings, part marking, and reliability data, see
IN
for
SHUTDOWN and RESET
SHUTDOWN (pin 12) and RESET (pin 13) are intended for
overriding the output MOSFET switch via external control
logic. The two inputs are fed through a latch preceding the
output switch. Depending on the logic state of RESET.
SHUTDOWN can be either a latched or unlatched input. The
output is off whenever SHUTDOWN is low. By simultaneously
having SHUTDOWN and RESET low, the latch is set and
SHUTDOWN has no effect until RESET goes high. See
Table TABLE 1.
Both pins have internal current source pull-ups and should be
left disconnected when not in use. An added feature of the
current sources is the ability to connect a capacitor and an
open-collector driver to the SHUTDOWN or RESET pins to
provide variable shutdown time.
Output Driver
The push-pull driver output has a typical on-resistance of 20-W
maximum switching times are specified at 75 ns for a 500-pF
load. This is sufficient to directly drive MOSFETs such as the
IRF820, BUZ78 or BUZ80. Larger devices can be driven, but
switching times will be longer, resulting in higher switching
losses.
TABLE 1.
TRUTH TABLE FOR SHUTDOWN AND
RESET PINS
SHUTDOWN
H
H
L
L
RESET
H
H
L
L
Normal Operation
Normal Operation (No Change)
Off (Not Latched)
Off (Latched)
Off (Latched—No Change)
S-42042—Rev. H, 15-Nov-04
Document Number: 70006
OUTPUT