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SI9120DY-T1-E3

P1-P3P4-P6P7-P9P10-P10
Si9120
Vishay Siliconix
www.vishay.com
4
Document Number: 70006
S-42042—Rev. H, 15-Nov-04
TIMING WAVEFORMS
90%
OUTPUT
SENSE
1.5 V −
50%
0
90%
OUTPUT
0 −
0 −
50%
50% 50%
50% 50%
RESET
0 −
t
d
t
r
10 ns
V
CC
V
CC
V
CC
t
SW
t
LW
t
RW
t
f
10 ns
V
CC
V
CC
t
SD
SHUTDOWN
SHUTDOWN
t
r
, t
f
10 ns
50%
0 −0 −
FIGURE 1. FIGURE 2.
FIGURE 3.
TYPICAL CHARACTERISTICS
Output Switching Frequency
vs. Oscillator Resistance
1 M
10 k
100 k
10 k
100 k 1 M
(Hz)f
OUT
r
OSC
− Oscillator Resistance (W)
Si9120
Vishay Siliconix
Document Number: 70006
S-42042—Rev. H, 15-Nov-04
www.vishay.com
5
PIN CONFIGURATIONS AND ORDERING INFORMATION
+V
IN
BIAS
NC*
Dual-In-Line
FB
NC* COMP
SENSE RESET
OUTPUT SHUTDOWN
−V
IN
V
REF
V
CC
DISCHARGE
OSC OUT OSC IN
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
Top View
+V
IN
BIAS
SOIC
FB
COMP
SENSE RESET
OUTPUT SHUTDOWN
−V
IN
V
REF
V
CC
DISCHARGE
OSC OUT OSC IN
1
4
5
6
7
8
16
15
14
13
12
11
10
9
Top View
Note: Pins 2 and 3 are removed
ORDERING INFORMATION
Part Number Temperature Range Package
Si9120DY
Si9120DY-T1 SOIC-16
Si9120DY-T1—E3 −40 to 85_C
Si9120DJ
PDIP 16
Si9120DJ—E3
PDIP-16
DETAILED DESCRIPTION
Pre-Regulator/Start-Up Section
Due to the low quiescent current requirement of the Si9120
control circuitry, bias power can be supplied from the
unregulated input power source, from an external regulated
low-voltage supply, or from an auxiliary “bootstrap” winding on
the output inductor or transformer.
When power is first applied during start-up, +V
IN
(pin 1) will
draw a constant current. The magnitude of this current is
determined by a high-voltage depletion MOSFET which is
connected between +V
IN
and V
CC
(pin 7). This start-up
circuitry provides initial power to the IC by charging an external
bypass capacitance connected to the V
CC
pin. The constant
current is disabled when V
CC
exceeds 8.6 V. If V
CC
is not
forced to exceed the 8.6-V threshold, then V
CC
will be
regulated to a nominal value of 8.6 V by the pre-regulator
circuit.
As the supply voltage rises toward the normal operating
conditions, an internal undervoltage (UV) lockout circuit keeps
the output driver disabled until V
CC
exceeds the undervoltage
lockout threshold (typically 8.1 V). This guarantees that the
control logic will be functioning properly and that sufficient gate
drive voltage is available before the MOSFET turns on. The
design of the IC is such that the undervoltage lockout threshold
will be at least 300 mV less than the pre-regulator turn-off
voltage. Power dissipation can be minimized by providing an
external power source to V
CC
such that the constant current
source is always disabled.
Note: When driving large MOSFETs at high frequency without
a bootstrap V
CC
supply, power dissipation in the pre-regulator
may exceed the power rating of the IC package. For operation
of +V
IN
> 250 V, a 10-kW,
1
/
4
-W resistor should be placed in
series with +V
IN
(Pin 1). For +V
IN
> 380 V, a 15-kW,
1
/
4
-W
resistor is recommended.
BIAS
To properly set the bias for the Si9120, a 390-kW resistor
should be tied from BIAS (pin 16) to −V
IN
(pin 6). This
determines the magnitude of bias current in all of the analog
sections and the pull-up current for the SHUTDOWN and
RESET pins. The current flowing in the bias resistor is
nominally 15 mA.
Si9120
Vishay Siliconix
www.vishay.com
6
Document Number: 70006
S-42042—Rev. H, 15-Nov-04
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
REF
) is internally connected to the output of the reference
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
IN
for
normal internal oscillator operation. A frequency divider in the
logic section limits switch duty cycle to 50% by locking the
switching frequency to one half of the oscillator frequency.
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.
TABLE 1.
TRUTH TABLE FOR SHUTDOWN AND
RESET PINS
SHUTDOWN RESET OUTPUT
H H Normal Operation
H Normal Operation (No Change)
L H Off (Not Latched)
L L Off (Latched)
L Off (Latched—No Change)
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.
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. For related documents such as package/tape drawings, part marking, and reliability data, see
http://www.vishay.com/ppg?70006.
P1-P3P4-P6P7-P9P10-P10

SI9120DY-T1-E3

Mfr. #:
Buy SI9120DY-T1-E3
Manufacturer:
Vishay / Siliconix
Description:
Switching Controllers Univ-Input Swmode Controller
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