APE1596C Format - Advanced Power Electronics Corp

Advanced Power
Electronics Corp.
APE1596C
3A/23V High Efficiency Synchronous Rectified Step-Down DC/DC Converter
FEATURES
DESCRIPTION
The APE1596C is a high efficiency synchronous stepdown DC/DC converter series with 3A continuous output
current supplied. Included on the substrate with the features
listed is a high performance trans-conductance error
amplifier that provides tight voltage regulation and accuracy
under transient conditions. A built-in under voltage lockout
circuit is provided to prevent start-up until the input voltage
reaches to 4.5V. In addition, it features over-current
protection and thermal shutdown. The APE1596C is
available in ESOP-8 package.
Input Voltage Supply Range from 4.5V to 23V
High Efficiency up to 95%
Adjustable Output Voltage from 0.925V to 12V
3A Continuous Output Current
330kHz Constant Frequency Operation
Current Mode Operation
Programmable Soft-start
Over-temperature Protection
Over-current Protection
Input Under Voltage Lockout
10μA Shutdown Current
ESOP-8 Package
RoHS Compliant & Halogen Free
APPLICATION
Data comm. xDSL CPE Graphics Cards
Set-Top-Box, DVD
Servers/Networking
DSP and FPGA Power Supply
Telecomm Equipments
DC-DC Regulator Modules
LCD Monitor and LCD TV
TYPICAL APPLICATION
Input
4.5 to 23V
BS
VIN
Cin
22 uF/25V
X5R
MLCC
Css
10 nF
EN
SS
APE1596C
VSW
COM
P
GND
Cbs
10 nF
L
10 uH
Output
3.3V
R1
26 .1 K
Cup
Option
FB
Cs
Cout
22 uFx2
X5 R
R2
10 K
Cp
Rc
Data and specifications subject to change without notice
1
20131210V1.0
Advanced Power
Electronics Corp.
APE1596C
PACKAGE ORDERING INFORMATION
( Top View )
APE1596 C X
BS
1
Package Type
VIN
2
MP : ESOP-8
SW
3
GND
4
8 SS
EXPOSED
PAD
7 EN
6
COMP
5
FB
ESOP-8
ABSOLUTE MAXIMUM RATINGS (at TA=25°C)
Input Supply Voltage(VIN) --------------------------------- +26V
SW PIN Voltage(VSW ) -------------------------------------- - 1V to 27V
SW PIN Voltage(VSW ) < 10ns----------------------------
- 5V to 30V
EN PIN Voltage(VEN) --------------------------------------- - 0.3 to VIN+0.3V
Other Pins Voltage -----------------------------------------
- 0.3V to +6V
Boost Voltage ------------------------------------------------ Vsw+6V
SW Peak Current -------------------------------------------
4.5A
Power Dissipation(PD)@TA=25oC ----------------------
1.96W
Storage Temperature Range(T ST) ---------------------- -65°C To 150°C
Junction Temperature Range(T j) -----------------------
-40°C To 150°C
Lead Temperature (Soldering 10s) --------------------- 260oC
Thermal Resistance from Junction to Case(Rth JC)
13°C/W
Thermal Resistance from Junction to Ambient(RthJA)
51°C/W
RECOMMENDED OPERATING CONDITIONS
Input Supply Voltage(VIN) --------------------------------- 4.5V to +23V
Operating Temperature -----------------------------------
-30°C To 85°C
Note 1: Stresses beyond above listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only
and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications are not
implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability.
Note 2: Guaranteed by design, not production tested.
Note3: For the measuring condition of Rthja, it is under the natural convection at TA = 25oC and on a four-layer test board with highly effective thermal
conductivity following the JEDEC 51-7 thermal measurement standard. As for the case position of Rthjc, it is on the exposed pad of the package.
ELECTRICAL SPECIFICATIONS
(Recommended Operating Conditions, Unless Otherwise Noted; VIN = 12V; TA = 25 oC)
Parameter
SYM
Supply Voltage
VIN
Shutdown Supply Current
ISD
TEST CONDITION
MIN
TYP
MAX
UNITS
4.5
-
23
V
VEN = 0V
-
10
-
uA
Regulated Feedback Voltage
4.5V≦VIN≦23V
0.9
0.925
0.95
V
Error Amplifier Transconductance
△ICOMP = +10uA
-
700
-
uA/V
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Advanced Power
Electronics Corp.
APE1596C
ELECTRICAL SPECIFICATIONS
Parameter
Current
Sense
Transconductance
SYM
to
TEST CONDITION
MIN
TYP
MAX
UNITS
-
2.2
-
A/V
-
4.3
-
A
-
-
10
uA
-
0.13
-
Ω
COMP
Current Limit
SW Leakage Current
VEN = 0V, VSW = 0V
High Side On Resistance
-
0.1
-
Ω
260
330
400
kHz
VFB=0.7V
-
90
-
%
-
100
-
ns
VIN Rising
3.85
4.1
4.35
V
-
250
-
mV
-
155
-
EN High Level
2.8
-
-
V
EN Low Level
-
-
1.2
V
4.2
Low Side On Resistance
Oscillation Frequency
Maximum Duty Cycle
Minimum On Time
Under Voltage Lockout Threshold
Under Voltage Lockout Threshold
Hysteresis
Thermal Shutdown Threshold
EN Input Current
VEN = 0V
3
Soft-Start Current
VSS=0V
5.3
Soft Start
Css=0.1uF
-
28
o
C
uA
uA
-
ms
o
Note: Fully production test at +25 C. Specifications over the temperature range are guaranteed by design and characterization.
PIN DESCRIPTIONS
PIN SYMBOL
BS
FB
EN
GND
PIN DESCRIPTION
It is required to connect SW and BS by a capacitor, which is able to boost the gate
drive to the internal NMOS above VIN to fully turn it ON.
This is the input to an error amplifier, which drives the PWM controller. It is necessary
to connect this pin to the actual output of power supply to set the DC output voltage.
This input provides an electrical ON/OFF control of the power supply. If the EN pin
is open, it will be pulled to high by the internal circuit.
This is the reference of the ground connection for all components in the power supply.
SW
This is the output of a power MOSFET switch.
VIN
The input voltage for the power supply is connected to this pin.
This pin is connected to an external capacitor, which is between the SS pin and
SS
GND to control soft-start time. This externally connected 0.1μF capacitor is able
to set the soft-start period to 28ms.
COMP
This pin is to compensate the regulation control loop by connecting a series of RC network
from COMP pin to GND pin.
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APE1596C
BLOCK DIAGRAM
Current Sense
Amplifier
EN
VIN
Slope Compensation
Σ
Reference
0.925V
VCS
PWM
Comparator
PWM
Error
Amplifier
FB
BS
UG
M1
PWM/
PSM
Logic
SW
Clock
Oscillator
LG
COMP
SS
M2
GND
FUNCTION PIN DESCRIPTION
The APE1596C is a current mode PWM synchronous step-down converter with a
constant switching frequency. It regulates the input voltage from 4.5V to 23V and a
low output voltage of 0.925V.The supplied load current is up to 3A.
Power Saving Mode
The switching losses resulted from the Miller capacitance of the MOSFET are the
dominant power dissipation parameters at light load. The power saving mode at light
load can minimize the switching loss by reducing the switching frequency. Therefore,
the APE1596C is designed as the power saving mode for high efficiency at light load.
Oscillator Frequency
Slope compensated current mode PWM control provides not only stable switching
and cycle-by-cycle current limit for superior load and line response but also protection
of the internal main switch and synchronous rectifier. The APE1596C switches at a
constant frequency (330 kHz) and regulates the output voltage. The PWM comparator
modulates the power transferred to the load by changing the inductor ’ s peak current
based on the feedback error voltage during each cycle. The main switch is turned on
for a certain period to ramp the inductor ’ s current at each rising edge of the internal
oscillator under normal operation whereas off when the inductor ’ s peak current is
above the error voltage. After the main switch is turned off, the low side MOS will be
turned on immediately and stay on until the next cycle starts.
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APE1596C
Short Circuit Protection
The APE1596C provides short circuit protection. When the output is shorted to
ground, the oscillator ’ s frequency is reduced to prevent the inductor ’ s current from
increasing beyond the NMOS current limit. The NMOS current limit is also reduced to
lower the short circuit current. The frequency and current limit will return to the normal
values once the short circuit condition is removed and the feedback voltage reaches
0.925V.
Maximum Load current
The APE1596C can operate down to 4.5V input voltage; however the maximum
load current decreases at lower input due to large IR voltage drop on the main switch
and low side switch. The slope compensation signal reduces the inductor ’ s peak
current as a function of the duty cycle to prevent sub-harmonic oscillations at duty
cycles greater than 50%.
Enable
The EN pin provides electrical on/off control of the regulator. Once the voltage of
the EN pin exceeds the threshold voltage, the regulator starts operation and the internal
slow start begins to ramp. If the voltage of the EN pin is pulled below the threshold, the
regulator will stop switching and the internal slow start reset. If the EN pin is open, it will
be pulled to high by the internal circuit.
Under Voltage Lockout
The APE1596C incorporates an under voltage lockout circuit to keep the device
disabled when VIN is below the UVLO start threshold. During power-up, the internal
circuit is held inactive until VIN exceeds the UVLO start threshold voltage. Once this
threshold voltage is reached, device start-up begins. The device operates until VIN falls
below the UVLO stop threshold voltage. The typical hysteretic in the UVLO comparator
is 250mV.
Soft-start
The built-in soft-start function is to gradually raise the output voltage after poweron. The soft-start period can be set by the external capacitor, which is between the SS
pin and GND.
CSS
TSS
10nF
100nF
2.8ms
28ms
Boost Capacitor
The BS pin and SW pin can be connected by a 10nF low ESR ceramic capacitor,
providing the gate drive voltage for the high side MOSFET.
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APE1596C
Thermal Shutdown
The APE1596C protects itself from overheating with an internal thermal shutdown
circuit. If the junction temperature exceeds the thermal shutdown threshold, the voltage
reference will be grounded and high side MOSFET turned off.
Compensation
The system stability is controlled through COMP pin. It will present a general
design procedure to ensure a stable and operational circuit. The design in this data
sheet is optimized for particular requirements. Some components may need to be
changed to ensure stability if there are different requirements. First of all, the power
components and their corresponding effects need to be determined. Following are the
compensation components, which are to produce stability.
The compensation steps for the converter are listed below:
(1). Choose an appropriate inductor and output capacitance based on the allowed
output voltage ripple and load transient.
(2). Placing FC as high as possible can respond quickly to the load transient.
Considering the output capacitor’s tolerances and temperature effects, typically place
FC approximately 1/10 of FS for the multi-layer ceramic output capacitor (X5R, X7R).
However, if the type of the output capacitor is the aluminum electrolytic or that largely
variable with the temperature, place FC approximately 1/20 of FS.
(3). Set the compensation RC to zero to cancel the RLOAD COUT pole.
RC =
2π × FC × COUT × VOUT
G M × G CS × VREF
CC =
COUT × R LOAD
RC
GM : error amp transconductance
GCS : current sense transconductance
(4). Determine CP if required. If ZESR (zero occurs by output capacitor ESR) is less than
FC, it should be cancelled with a pole set by capacitor CP connected between CC to
GND.
C P = C OUT ×
R ESR
RC
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APE1596C
APPLICATION INFORMATION
Input Capacitor Selection
It is necessary for the input capacitor to sustain the ripple current produced during
the period of “on” state of the upper MOSFET, so a low ESR is required to minimize the
loss. The RMS value of this ripple can be obtained by the following:
I IN RMS = I OUT
D × (1 − D )
Where D is the duty cycle, linRMS is the input RMS current, and IOUT is the load
current. The equation reaches its maximum value with D = 0.5. The loss of the input
capacitor can be calculated by the following equation:
PCIN = ESR CIN × I IN RMS 2
Where PCIN is the power loss of the input capacitor and ESRCIN is the effective
series resistance of the input capacitance. Due to large dI/dt through the input
capacitor, electrolytic or ceramics should be used. If a tantalum must be used, it must
be surge-protected. Otherwise, capacitor failure could occur.
Output Inductor Selection
The output inductor selection is to meet the requirements of the output voltage
ripple and affects the load transient response. The higher inductance can reduce the
inductor's ripple current and induce the lower output ripple voltage. The ripple voltage
and current can be approximately calculated approximated by the following equations:
∆I =
V in − V out V out
•
FS × L
Vin
∆ Vout = ∆ I × ESR
Although the increase of the inductance reduces the ripple current and voltage, it
contributes to the decrease of the response time for the regulator to load transient as
well. Increasing the switching frequency (Fs) for a given inductor also can reduce the
ripple current and voltage but it will increase the switching loss of the power MOS.
The way to set a proper inductor value is to have the ripple current ( △ I) be
approximately 10%~50% of the maximum output current. Once the value has been
determined, select an inductor capable of carrying the required peak current without
going into saturation. It is also important to have the inductance tolerance specified to
keep the accuracy of the system controlled. Using 20% for the inductance (at room
temperature) is reasonable tolerance able to be met by most manufacturers. For some
types of inductors, especially those with core made of ferrite, the ripple current will
increase abruptly when it saturates, resulting in a larger output ripple voltage.
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APE1596C
Output Capacitors Selection
An output capacitor is required to filter the output and supply the load transient
current. The high capacitor value and low ESR will reduce the output ripple and the
load transient drop. These requirements can be met by a mix of capacitors and careful
layout.
In typical switching regulator design, the ESR of the output capacitor bank
dominates the transient response. The number of output capacitors can be determined
by the following equations:
∆VESR
ESR MAX =
∆I OUT
Number
Of
Capacitors =
ESR CAP
ESR MAX
△VESR = change in output voltage due to ESR
(assigned by the designer)
△IOUT = load transient.
ESRCAP = maximum ESR per capacitor (specified in manufacturer’s data sheet).
ESRMAX = maximum allowable ESR.
High frequency decoupling capacitors should be placed as close to the power pins of
the load as physically possible. For the decoupling requirements, please consult the
capacitor manufacturers for confirmation.
Output Voltage
The output voltage is set using the FB pin and a resistor divider connected to the
output as shown in the following AP Circuit. The output voltage (VOUT) can be
calculated according to the voltage of the FB pin (VFB) and ratio of the feedback
resistors by the following equation, where (VFB) is 0.925V:
VFB = Vout ×
R2
( R1 + R 2 )
Vout = 0 .925 ×
( R1 + R 2 )
R2
Thus the output voltage is:
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APE1596C
External Bootstrap Diode
When VIN <5.5V or Duty Cycle>65% condition, it is strongly recommended to add
an external bootstrap diode (such as IN4148 or BAT54) between an external 5V and
BST pin for efficiency improvement. The external 5V should be lower than 5.5V.
5V
VIN
BS
10nF
APE1596C
SW
This diode is also recommended for high duty cycle operation when Duty
Cycle>65% (Example: VIN=5V & VOUT=3.3V; Duty Cycle=66%) and high output voltage
(VOUT>12V) applications.
Layout Consideration
For proper operation of the converter, some layout rules should be followed. It is
necessary to understand which pin of APE1596C is sensitive and which is insensitive.
Please refer the following for the location where noise comes from on the circuit and
where the clear ground is for the small signal ground.
R2
10K
Input
4.5 to 2 3V
FB
VIN
BS
C bs
1 0 nF
L
1 0 uH
C in
2 2 uF/ 2 5V
EN
APE1596C
SW
R1
2 6 .1 K
Output
3.3 V/3A
SS
Css
GN D
C OM
P
Cp
C out
2 2uF/6 .3 V x 2
C e ra m ic
Cs
Rs
PGN D R e turn
Pa th
1.) First, put the input capacitor (CIN) as close as possible to the VIN pin.
2.) Secondly, place the Cs, Rs, Cp, Css and R2 as close as APE1596C and connect
these analog grounds (Clear AGND) to APE1596C ’ s GND pin. It is recommended to
use a dot short for these AGND pins or connect the GND pin via contact.
3.) The large current loop shown in bold lines in the above figure circuit should be
routed as short and wide as possible and the switch node is a high dv/dt. It easily
couples noise to other traces by the capacitive path. Therefore the sensitive signals like
FB, COMP and AGND should be routed away with this noise source.
4.) The feedback network resistors (R1 & R2) should be routed away from the inductor
and switch node to minimize noise and EMI issue. And the R1 resistor should be
sensed the output capacitor or device loading, not the inductor’s output node.
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APE1596C
PCB Layout Guide
Top Layer
Bottom Layer (Top view)
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APE1596C
APE1596C EVB Schematic
Application 1
C12
NC
R1
R2
10K
U1
APE1596 C
GND
SW
VCC
BST
1
2
Vin
12V
BST
R3
C9
10nF
Vout
L1
SW
C1
22uF
C5
C6
0.1uF 22uF /25V
9
C7
FB
COMP
EN
SS
EP
FB
COMP
EN
SS
C13
NC
R5
NC
C2
22uF
C8
C10
10nF
Vin
R4 100 K
EN
Qty
Ref
Value
Description
Package
2
C1, C2,
22µF
Ceramic Capacitor X5R 16V
1
C6
22uF
Ceramic Capacitor X5R 25V
1206
1
C5
0.1µF
Ceramic Capacitor
0603
1
L1
10uH
1
R4
Inductor, Rated Current 4.5A
WE-part number: 744 771 4100---10uH
100KΩ
Vout=12V
120K Ω
Vout=5V
44.2KΩ
1206
SMD
Resistor, ±1%
0603
Resistor, ±1%
0603
Resistor, ±1%
0603
Ceramic Capacitor
0603
C7 value is adjustable for the ESR of
Cout.
0603
Ceramic Capacitor
0603
Step-Down DC/DC Converter
ESOP-8
Vout=3.3V 26.1KΩ
1
R1
Vout=2.5V 17.4KΩ
Vout=1.8V 9.53KΩ
Vout=1.5V 6.34KΩ
Vout=1.2V 3K Ω
Vout=1V
1
R2
820Ω
10k Ω
Vout=12V
60.4KΩ
Vout=5V
30.9KΩ
Vout=3.3V 21KΩ
1
R3
Vout=2.5V 16KΩ
Vout=1.8V 4.7K Ω
Vout=1.5V 4.7K Ω
Vout=1.2V 3.9K Ω
Vout=1V
3
3.0K Ω
C9, C10, C11 10nF
Vout=12V
18pF
Vout=5V
33pF
Vout=3.3V 47pF
1
C7
Vout=2.5V 68pF
Vout=1.8V 100pF
Vout=1.5V 120pF
Vout=1.2V 150pF
Vout=1V
180pF
Vout=12V
3.3nF
Vout=5V
3.3nF
Vout=3.3V 3.3nF
1
C8
Vout=2.5V 3.3nF
Vout=1.8V 8.2nF
Vout=1.5V 8.2nF
Vout=1.2V 8.2nF
Vout=1V
1
U1
8.2nF
APE1596CMP
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APE1596C
Application 2
C12 NC
R1
R2
10K
U1
APE1596C
R3
C9
0.1uF
9
C7
FB
COMP
EN
SS
EP
FB
COMP
EN
SS
C13
NC
R5
NC
GND
SW
VCC
BST
Vout
L1
SW
1
2
Vin
12V
BST
C5
C6
0.1uF 22uF/25V
C1
10uF
C4
470uF
C8
C10
10nF
Vin
R4
100K
EN
Qty
Ref
Description
Value
Package
1
C6
22µF
Ceramic Capacitor X5R 25V
1
C1
10uF
Ceramic Capacitor X5R 16V
1206
1
C4
470uF
EC470uF/Breakdown Voltage > 2~3 time Vo
6.3x11mm( DIP)
2
C5,C9
0.1µF
Ceramic Capacitor
0603
1206
Inductor, Rated Current 4.5A
1
L1
10uH
WE-part number: 744 771 4100---10uH
SMD
1
R4
100K Ω
Resistor, ±1%
0603
Resistor, ±1%
0603
Vout=12V
120K Ω
Vout=5V
44.2K Ω
Vout=3.3V 26.1K Ω
Vout=2.5V 17.4K Ω
Vout=1.8V 9.53K Ω
Vout=1.5V 6.34K Ω
Vout=1.2V 3KΩ
1
R1
Vout=1V
1
R2
10k Ω
820Ω
Vout=12V
250K Ω
Vout=5V
120K Ω
Vout=3.3V 75K Ω
Vout=2.5V 59K Ω
Vout=1.8V 47K Ω
Vout=1.5V 33K Ω
Vout=1.2V 27K Ω
1
R3
Vout=1V
2
C10, C11
10nF
22K Ω
Vout=12V
470pF
Vout=5V
470pF
Resistor, ±1%
0603
Ceramic Capacitor
0603
C7 value is adjustable for the ESR of Cout.
0603
Vout=3.3V 470pF
Vout=2.5V 470pF
Vout=1.8V 470pF
Vout=1.5V 470pF
Vout=1.2V 470pF
1
C7
Vout=1V
470pF
Vout=12V
4.7nF
4.7nF
Vout=5V
Vout=3.3V 4.7nF
Vout=2.5V 4.7nF
Vout=1.8V 4.7nF
Vout=1.5V 4.7nF
1
C8
Vout=1.2V 4.7nF
4.7nF
Vout=1V
Ceramic Capacitor
0603
1
U1
APE1596CMP
Step-Down DC/DC Converter
ESOP-8
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APE1596C
TYPICAL PERFORMANCE CHARACTERISTICS
VIN=12V, VOUT=3.3V, Io=0.5A
VIN=12V, VOUT=3.3V, Io=0.5A
VIN=12V, VOUT=3.3V, 0.5A
VIN=12V, VOUT=3.3V
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APE1596C
TYPICAL PERFORMANCE CHARACTERISTICS
Load Transient Response
VIN=12V, VOUT=3.3V, IOUT=0.5A~1A
VO(Ac)
(50mV/Div)
Load Transient Response
VIN=12V, VOUT=3.3V, IOUT=1.5A~3A
VO(Ac)
(200mV/Div)
Io
(0.5A/Div)
Io
(2A/Div)
Time: (200uS/Div)
Power On
VIN=12V, VOUT=3.3V, IOUT=No Load
Time: (200uS/Div)
Power Off
VIN=12V, VOUT=3.3V, IOUT=No Load
VIN
(5V/Div)
VIN
(5V/Div)
VO
(2V/Div)
VO
(2V/Div)
Sw
(10V/Div
Sw
(10V/Div
IL
(2A/Div)
IL
(2A/Div)
Time: (2mS/Div)
Power On
VIN=12V, VOUT=3.3V, IOUT=3A
Time: (200mS/Div)
Power Off
VIN=12V, VOUT=3.3V, IOUT=3A
VIN
(5V/Div)
VIN
(5V/Div)
VO
(2V/Div)
VO
(2V/Div)
Sw
(10V/Div
IL
(2A/Div)
Sw
(10V/Div
IL
(2A/Div)
Time: (2mS/Div)
Time: (200mS/Div)
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APE1596C
TYPICAL PERFORMANCE CHARACTERISTICS
Steady State Waveforms
VIN=12V, VOUT=3.3V, IOUT=10mA
Steady State Waveforms
VIN=12V, VOUT=3.3V, IOUT=3A
VIN
(500mV/Div)
VIN
(500mV/Div
)
Vo(AC)
(20mV/Div)
Vo(AC)
(20mV/Div)
Sw
(10V/Div
)
Sw
(10V/Div
)
IL
(2A/Div)
IL
(200mA/Div)
Time: (10uS/Div)
Time: (4uS/Div)
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APE1596C
MARKING INFORMATION
ESOP-8
Part Number
Package Code
1596CMP
YWWSSS
Date Code (YWWSSS)
Y:Last Digit Of The Year
WW:Week
SSS:Sequence
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