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LM3488, LM3488-Q1
SNVS089N – JULY 2000 – REVISED DECEMBER 2014
LM3488/-Q1 High-Efficiency, Low-Side, N-Channel Controller for Switching Regulators
1 Features
3 Description
•
The LM3488 is a versatile low-side N-FET highperformance controller for switching regulators. This
device is suitable for use in topologies requiring lowside FET, such as boost, flyback, or SEPIC.
Moreover, the LM3488 can be operated at extremely
high switching frequency to reduce the overall
solution size. The switching frequency of LM3488 can
be adjusted to any value from 100 kHz to 1 MHz by
using a single external resistor or by synchronizing it
to an external clock. Current mode control provides
superior bandwidth and transient response, besides
cycle-by-cycle current limiting. Output current can be
programmed with a single external resistor.
1
•
•
•
•
•
•
•
•
LM3488-Q1 is AEC-Q100 Qualified and
Manufactured on an Automotive-Grade Flow
8-Lead VSSOP Package
Internal Push-Pull Driver With 1-A Peak Current
Capability
Current Limit and Thermal Shutdown
Frequency Compensation Optimized With a
Capacitor and a Resistor
Internal Soft-Start
Current Mode Operation
Undervoltage Lockout With Hysteresis
Key Specifications:
– Wide Supply Voltage Range of 2.97 V to 40 V
– 100-kHz to 1-MHz Adjustable and
Synchronizable Clock Frequency
– ±1.5% (Overtemperature) Internal Reference
– 5-µA Shutdown Current (Overtemperature)
•
•
Device Information(1)
PART NUMBER
2 Applications
•
•
The LM3488 has built-in features such as thermal
shutdown, short-circuit protection, and overvoltage
protection. Power-saving shutdown mode reduces the
total supply current to 5 µA and allows power supply
sequencing. Internal soft-start limits the inrush current
at start-up.
LM3488
Distributed Power Systems
Notebook, PDA, Digital Camera, and other
Portable Applications
Offline Power Supplies
Set-Top Boxes
LM3488-Q1
PACKAGE
BODY SIZE (NOM)
VSSOP (8)
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Typical SEPIC Converter
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM3488, LM3488-Q1
SNVS089N – JULY 2000 – REVISED DECEMBER 2014
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
6.1
6.2
6.3
6.4
6.5
6.6
6.7
3
4
4
4
4
4
7
Absolute Maximum Ratings .....................................
Handling Ratings : LM3488.......................................
Handling Ratings: LM3488-Q1..................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 11
7.1 Overview ................................................................. 11
7.2 Functional Block Diagram ....................................... 12
7.3 Feature Description................................................. 12
7.4 Device Functional Modes........................................ 16
8
Application and Implementation ........................ 17
8.1 Application Information............................................ 17
8.2 Typical Applications ................................................ 17
9 Power Supply Recommendations...................... 28
10 Layout................................................................... 28
10.1 Layout Guidelines ................................................. 28
10.2 Layout Example .................................................... 29
11 Device and Documentation Support ................. 29
11.1
11.2
11.3
11.4
Related Links ........................................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
29
30
30
30
12 Mechanical, Packaging, and Orderable
Information ........................................................... 30
4 Revision History
Changes from Revision M (March 2013) to Revision N
•
Page
Added Pin Configuration and Functions section, Handling Rating table, Feature Description section, Device
Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout
section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information
section ................................................................................................................................................................................... 1
Changes from Revision L (March 2013) to Revision M
•
2
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 29
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5 Pin Configuration and Functions
8-Pin DGK
VSSOP Package
Top View
Pin Functions
PIN
TYPE
DESCRIPTION
NAME
NO.
ISEN
1
I
Current sense input pin. Voltage generated across an external sense resistor is fed into this pin.
COMP
2
A
Compensation pin. A resistor, capacitor combination connected to this pin provides compensation for the
control loop.
FB
3
I
Feedback pin. The output voltage should be adjusted using a resistor divider to provide 1.26 V at this pin.
AGND
4
P
Analog ground pin.
PGND
5
P
Power ground pin.
DR
6
O
Drive pin of the IC. The gate of the external MOSFET should be connected to this pin.
FA/SYNC/S
D
7
A
Frequency adjust, synchronization, and Shutdown pin. A resistor connected to this pin sets the oscillator
frequency. An external clock signal at this pin will synchronize the controller to the frequency of the clock.
A high level on this pin for ≥ 30 µs will turn the device off. The device will then draw less than 10µA from
the supply.
VIN
8
P
Power supply input pin.
6 Specifications
6.1 Absolute Maximum Ratings
(1)
MIN
MAX
UNIT
45
V
–0.4 < VFB
VFB < 7
V
–0.4 < VFA/SYNC/SD
VFA/SYNC/SD < 7
V
1
A
Input voltage
FB pin voltage
FA/SYNC/SD pin voltage
Peak driver output current (< 10 µs)
Power dissipation
Internally Limited
Junction temperature
Lead temperature
Vapor Phase (60 s)
Infared (15 s)
−0.4 ≤ VDR
DR pin voltage
ILIM pin voltage
(1)
150
°C
215
°C
260
°C
VDR ≤ 8
V
600
mV
Absolute Maximum Ratings are limits beyond which damage to the device may occur. Recommended Operating Conditions are
conditions under which operation of the device is intended to be functional. For specifications and test conditions, see the Electrical
Characteristics.
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6.2 Handling Ratings : LM3488
Tstg
V(ESD)
(1)
(2)
MIN
MAX
UNIT
–65
150
°C
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all
pins (1)
–2000
2000
Charged device model (CDM), per JEDEC specification
JESD22-C101, all pins (2)
–750
750
Storage temperature range
Electrostatic discharge
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Handling Ratings: LM3488-Q1
MIN
Tstg
Storage temperature range
(1)
Electrostatic discharge
Charged device model (CDM), per
AEC Q100-011
UNIT
°C
–65
150
–2000
2000
Corner pins (1, 4, 5,
and 8)
–750
750
Other pins
–750
750
Human body model (HBM), per AEC Q100-002 (1)
V(ESD)
MAX
V
AEC Q100-002 indicates HBM stressing is done in accordance with the ANSI/ESDA/JEDEC JS-001 specification.
6.4 Recommended Operating Conditions
Supply Voltage
Junction Temperature Range
MIN
MAX
2.97 ≤ VIN
VIN ≤ 40
V
−40 ≤ TJ
TJ ≤ 125
°C
100 ≤ FSW
Switching Frequency
UNIT
FSW ≤ 1 kHz/MH
z
6.5 Thermal Information
LM3488,
LM3488-Q1
THERMAL METRIC (1)
UNIT
DGK
8 PINS
RθJA
Junction-to-ambient thermal resistance
160
RθJC(top)
Junction-to-case (top) thermal resistance
50
RθJB
Junction-to-board thermal resistance
77
ψJT
Junction-to-top characterization parameter
4.7
ψJB
Junction-to-board characterization parameter
76
(1)
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
6.6 Electrical Characteristics
Unless otherwise specified, VIN = 12 V, RFA = 40 kΩ, TJ = 25°C
PARAMETER
VFB
TEST CONDITIONS
Feedback Voltage
MIN
TYP
MAX
VCOMP = 1.4 V, 2.97 ≤ VIN ≤ 40 V
1.2507
1.26
1.2753
VCOMP = 1.4 V, 2.97 ≤ VIN ≤ 40 V,
−40°C ≤ TJ ≤ 125°C
1.24
UNIT
V
1.28
ΔVLINE
Feedback Voltage Line Regulation
2.97 ≤ VIN ≤ 40 V
0.001
%/V
ΔVLOAD
Output Voltage Load Regulation
IEAO Source/Sink
±0.5
%/V
(max)
VUVLO
Input Undervoltage Lock-out
2.85
V
VUV(HYS)
Input Undervoltage Lock-out Hysteresis
−40°C ≤ TJ ≤ 125°C
2.97
170
−40°C ≤ TJ ≤ 125°C
4
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130
mV
210
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Electrical Characteristics (continued)
Unless otherwise specified, VIN = 12 V, RFA = 40 kΩ, TJ = 25°C
PARAMETER
Fnom
TEST CONDITIONS
Nominal Switching Frequency
RFA = 40 KΩ
RFA = 40 KΩ, −40°C ≤ TJ ≤ 125°C
Maximum Duty Cycle (2)
Tmin (on)
Minimum On Time
IQ
400
360
4.5
Ω
VIN
V
VIN ≥ 7.2 V
7.2
100%
325
Supply Current (switching)
Quiescent Current in Shutdown Mode
See
(3)
See
(3)
230
Current Sense Threshold Voltage
VSC
Short-Circuit Current Limit Sense Voltage
VSL
Internal Compensation Ramp Voltage
2.7
, −40°C ≤ TJ ≤ 125°C
5
VSL ratio
VSL/VSENSE
VOVP
Output Overvoltage Protection (with
respect to feedback voltage) (5)
135
VIN = 5 V, −40°C ≤ TJ ≤ 125°C
125
VIN = 5 V
0.30
0.49
0.70
32
50
78
VCOMP = 1.4 V, −40°C ≤ TJ ≤
125°C
25
VCOMP = 1.4 V, IEAO = 100 µA
(Source/Sink)
600
VCOMP = 1.4 V, IEAO = 100 µA
(Source/Sink), −40°C ≤ TJ ≤ 125°C
365
(1)
(2)
(3)
(4)
(5)
mV
132
VCOMP = 1.4 V
Gm
mV
85
60
VCOMP = 1.4 V, IEAO = 100 µA
(Source/Sink)
Error Amplifier Output Current (Source/
Sink)
mV
415
52
20
IEAO
mV
92
VCOMP = 1.4 V, −40°C ≤ TJ ≤
125°C
Error Amplifier Voltage Gain
180
190
250
VIN = 5 V
VCOMP = 1.4 V
AVOL
156
343
VOVP(HYS) Output Over-Voltage Protection
Hysteresis (5)
Error Ampifier Transconductance
µA
7
VIN = 5 V
VIN = 5 V, −40°C ≤ TJ ≤ 125°C
mA
3.0
VFA/SYNC/SD = 5 V (4), VIN = 5 V
VIN = 5 V, −40°C ≤ TJ ≤ 125°C
nsec
550
VFA/SYNC/SD = 5 V (4), VIN = 5 V,
−40°C ≤ TJ ≤ 125°C
VSENSE
kHz
430
VIN < 7.2 V
−40°C ≤ TJ ≤ 125°C
ISUPPLY
UNIT
IDR = 0.2A
RDS2 (ON) Driver Switch On Resistance (bottom)
Dmax
MAX
Ω
IDR = 0.2A, VIN= 5 V
Maximum Drive Voltage Swing (1)
TYP
16
RDS1 (ON) Driver Switch On Resistance (top)
VDR (max)
MIN
mV
110
800
1000
µmho
1265
38
VCOMP = 1.4 V, IEAO = 100 µA
(Source/Sink), −40°C ≤ TJ ≤ 125°C
26
Source, VCOMP = 1.4 V, VFB = 0 V
80
Source, VCOMP = 1.4 V, VFB = 0 V,
−40°C ≤ TJ ≤ 125°C
50
Sink, VCOMP = 1.4 V, VFB = 1.4 V
−100
Sink, VCOMP = 1.4 V, VFB = 1.4 V,
−40°C ≤ TJ ≤ 125°C
−85
V/V
44
110
140
µA
180
−140
−180
µA
−185
The voltage on the drive pin, VDR is equal to the input voltage when input voltage is less than 7.2 V. VDR is equal to 7.2 V when the
input voltage is greater than or equal to 7.2 V.
The limits for the maximum duty cycle can not be specified since the part does not permit less than 100% maximum duty cycle
operation.
For this test, the FA/SYNC/SD Pin is pulled to ground using a 40K resistor .
For this test, the FA/SYNC/SD Pin is pulled to 5 V using a 40K resistor.
The over-voltage protection is specified with respect to the feedback voltage. This is because the over-voltage protection tracks the
feedback voltage. The over-voltage thresold can be calculated by adding the feedback voltage, VFB to the over-voltage protection
specification.
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Electrical Characteristics (continued)
Unless otherwise specified, VIN = 12 V, RFA = 40 kΩ, TJ = 25°C
PARAMETER
VEAO
TEST CONDITIONS
Error Amplifier Output Voltage Swing
MIN
Upper Limit: VFB = 0 V, COMP Pin
= Floating
TYP
MAX
2.2
Upper Limit: VFB = 0 V, COMP Pin
= Floating, −40°C ≤ TJ ≤ 125°C
1.8
Lower Limit: VFB = 1.4 V
V
2.4
0.56
Lower Limit: VFB = 1.4 V, −40°C ≤
TJ ≤ 125°C
UNIT
0.2
V
1.0
TSS
Internal Soft-Start Delay
VFB = 1.2 V, VCOMP = Floating
4
ms
Tr
Drive Pin Rise Time
Cgs = 3000 pf, VDR = 0 to 3 V
25
ns
Tf
Drive Pin Fall Time
Cgs = 3000 pf, VDR = 0 to 3 V
25
ns
VSD
Shutdown and Synchronization signal
threshold (6)
Output = High
1.27
V
Output = High, −40°C ≤ TJ ≤ 125°C
1.4
Output = Low
0.65
V
VSD = 5 V
−1
µA
VSD = 0 V
+1
Output = Low, −40°C ≤ TJ ≤ 125°C
ISD
Shutdown Pin Current
IFB
Feedback Pin Current
TSD
Thermal Shutdown
Tsh
Thermal Shutdown Hysteresis
(6)
6
0.3
15
nA
165
°C
10
°C
The FA/SYNC/SD pin should be pulled to VIN through a resistor to turn the regulator off.
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6.7 Typical Characteristics
Unless otherwise specified, VIN = 12V, TJ = 25°C.
Figure 1. IQ vs Temperature & Input Voltage
Figure 2. ISupply vs Input Voltage (Non-Switching)
Figure 3. ISupply vs VIN
Figure 4. Switching Frequency vs RFA
Figure 5. Frequency vs Temperature
Figure 6. Drive Voltage vs Input Voltage
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Typical Characteristics (continued)
Unless otherwise specified, VIN = 12V, TJ = 25°C.
8
Figure 7. Current Sense Threshold vs Input Voltage
Figure 8. COMP Pin Voltage vs Load Current
Figure 9. Efficiency vs Load Current (3.3 V In and 12 V Out)
Figure 10. Efficiency vs Load Current (5 V In and 12 V Out)
Figure 11. Efficiency vs Load Current (9 V In and 12 V Out)
Figure 12. Efficiency vs Load Current (3.3 V In and 5 V Out)
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Typical Characteristics (continued)
Unless otherwise specified, VIN = 12V, TJ = 25°C.
Figure 13. Error Amplifier Gain
Figure 14. Error Amplifier Phase
Figure 15. COMP Pin Source Current vs Temperature
Figure 16. Short Circuit Protection vs Input Voltage
Figure 17. Compensation Ramp vs Compensation Resistor
Figure 18. Shutdown Threshold Hysteresis vs Temperature
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Typical Characteristics (continued)
Unless otherwise specified, VIN = 12V, TJ = 25°C.
Figure 19. Current Sense Voltage vs Duty Cycle
10
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7 Detailed Description
7.1 Overview
The LM3488 uses a fixed frequency, Pulse Width Modulated (PWM), current mode control architecture. In a
typical application circuit, the peak current through the external MOSFET is sensed through an external sense
resistor. The voltage across this resistor is fed into the ISEN pin. This voltage is then level shifted and fed into the
positive input of the PWM comparator. The output voltage is also sensed through an external feedback resistor
divider network and fed into the error amplifier negative input (feedback pin, FB). The output of the error amplifier
(COMP pin) is added to the slope compensation ramp and fed into the negative input of the PWM comparator.
At the start of any switching cycle, the oscillator sets the RS latch using the SET/Blank-out and switch logic
blocks. This forces a high signal on the DR pin (gate of the external MOSFET) and the external MOSFET turns
on. When the voltage on the positive input of the PWM comparator exceeds the negative input, the RS latch is
reset and the external MOSFET turns off.
The voltage sensed across the sense resistor generally contains spurious noise spikes, as shown in Figure 20.
These spikes can force the PWM comparator to reset the RS latch prematurely. To prevent these spikes from
resetting the latch, a blank-out circuit inside the IC prevents the PWM comparator from resetting the latch for a
short duration after the latch is set. This duration is about 150ns and is called the blank-out time.
Under extremely light load or no-load conditions, the energy delivered to the output capacitor when the external
MOSFET is on during the blank-out time is more than what is delivered to the load. An over-voltage comparator
inside the LM3488 prevents the output voltage from rising under these conditions. The over-voltage comparator
senses the feedback (FB pin) voltage and resets the RS latch under these conditions. The latch remains in reset
state till the output decays to the nominal value.
Figure 20. Basic Operation of the PWM Comparator
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7.2 Functional Block Diagram
7.3 Feature Description
7.3.1 Slope Compensation Ramp
The LM3488 uses a current mode control scheme. The main advantages of current mode control are inherent
cycle-by-cycle current limit for the switch, and simpler control loop characteristics. It is also easy to parallel power
stages using current mode control since as current sharing is automatic.
Current mode control has an inherent instability for duty cycles greater than 50%, as shown in Figure 21. In
Figure 21, a small increase in the load current causes the switch current to increase by ΔIO. The effect of this
load change, ΔI1, is :
(1)
From the above equation, when D > 0.5, ΔI1 will be greater than ΔIO. In other words, the disturbance is divergent.
So a very small perturbation in the load will cause the disturbance to increase.
To prevent the sub-harmonic oscillations, a compensation ramp is added to the control signal, as shown in
Figure 22.
12
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Feature Description (continued)
With the compensation ramp,
(2)
Figure 21. Sub-Harmonic Oscillation for D>0.5
Figure 22. Compensation Ramp Avoids Sub-Harmonic Oscillation
The compensation ramp has been added internally in LM3488. The slope of this compensation ramp has been
selected to satisfy most of the applications. The slope of the internal compensation ramp depends on the
frequency. This slope can be calculated using the formula:
MC = VSL.FS Volts/second
(3)
In the above equation, VSL is the amplitude of the internal compensation ramp. Limits for VSL have been specified
in the electrical characteristics.
In order to provide the user additional flexibility, a patented scheme has been implemented inside the IC to
increase the slope of the compensation ramp externally, if the need arises. Adding a single external resistor,
RSL(as shown in Figure 23) increases the slope of the compensation ramp, MC by :
.
.
40x10-6 RSL FS Amps
'MC =
second
RSEN
(4)
-6
In this equation, ΔVSL is equal to 40.10 RSL. Hence,
(5)
ΔVSL versus RSL has been plotted in Figure 24 for different frequencies.
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Feature Description (continued)
Figure 23. Increasing the Slope of the Compensation Ramp
Figure 24. ΔVSL vs RSL
7.3.2 Frequency Adjust/Synchronization/Shutdown
The switching frequency of LM3488 can be adjusted between 100kHz and 1MHz using a single external resistor.
This resistor must be connected between FA/SYNC/SD pin and ground, as shown in Figure 25. See Typical
Characteristics to determine the value of the resistor required for a desired switching frequency.
The LM3488 can be synchronized to an external clock. The external clock must be connected to the
FA/SYNC/SD pin through a resistor, RSYNC as shown in Figure 26. The value of this resistor is dependent on the
off time of the synchronization pulse, TOFF(SYNC). Table 1 shows the range of resistors to be used for a given
TOFF(SYNC).
Table 1. Recommended Series Resistance for
Synchronization
TOFF(SYNC) (µs)
14
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RSYNC range (kΩ)
1
5 to 13
2
20 to 40
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Table 1. Recommended Series Resistance for
Synchronization (continued)
TOFF(SYNC) (µs)
RSYNC range (kΩ)
3
40 to 65
4
55 to 90
5
70 to 110
6
85 to 140
7
100 to 160
8
120 to 190
9
135 to 215
10
150 to 240
It is also necessary to have the width of the synchronization pulse wider than the duty cycle of the converter
(when DR pin is high and the switching point is low). It is also necessary to have the synchronization pulse width
≥ 300nsecs.
The FA/SYNC/SD pin also functions as a shutdown pin. If a high signal (see Electrical Characteristics for
definition of high signal) appears on the FA/SYNC/SD pin, the LM3488 stops switching and goes into a low
current mode. The total supply current of the IC reduces to less than 10µA under these conditions.
Figure 27 and Figure 28 show implementation of shutdown function when operating in Frequency adjust mode
and synchronization mode respectively. In frequency adjust mode, connecting the FA/SYNC/SD pin to ground
forces the clock to run at a certain frequency. Pulling this pin high shuts down the IC. In frequency adjust or
synchronization mode, a high signal for more than 30µs shuts down the IC.
Figure 29 shows implementation of both frequency adjust with RFA resistor and frequency synchronization with
RSYNC. The switching frequency is defined by RFA when a synchronization signal is not applied. When sync is
applied it overrides the RFA setting.
Figure 25. Frequency Adjust
Figure 26. Frequency Synchronization
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Figure 27. Shutdown Operation in Frequency Adjust Mode
Figure 28. Shutdown Operation in Synchronization Mode
RSYNC
CSYNC
FA/SYNC/SD
270 pF
LM3488
RFA
Figure 29. Frequency Adjust or Frequency Synchronization
7.3.3 Short-Circuit Protection
When the voltage across the sense resistor (measured on ISEN Pin) exceeds 350mV, short-circuit current limit
gets activated. A comparator inside LM3488 reduces the switching frequency by a factor of 5 and maintains this
condition till the short is removed.
7.4 Device Functional Modes
The device is set to run as soon as the input voltage crosses above the UVLO set point and at a frequency set
according to the FA/SYNC/SD pin pull-down resistor or to run at a frequency set by the waveform applied to the
FA/SYNC/SD pin.
If the FA/SYNC/SD pin is pulled high, the LM3488 enters shut-down mode.
If the voltage at the ISEN pin exceeds Vsc, the device enters short-circuit protection mode.
16
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LM3488 may be operated in either continuous or discontinuous conduction mode. The following applications
are designed for continuous conduction operation. This mode of operation has higher efficiency and lower EMI
characteristics than the discontinuous mode.
8.2 Typical Applications
8.2.1 Boost Converter
VIN = 3.3V (±10%)
+
CIN
100 PF, 6.3V
L
10 PH
ISEN
VIN
CC 22 nF
COMP
RC
4.7k
D MBRD340
RFA
20k
FA/SD/SYNC
FB
+ COUT
40k
LM3488
100 PF, 10V
x2
Q1
IRF7807
DR
RF1
AGND
VOUT = 5V, 2A
60k
RF2
PGND
CSN
0.01 PF
RSN
0.025:
Figure 30. Typical High Efficiency Step-Up (Boost) Converter
The most common topology for LM3488 is the boost or step-up topology. The boost converter converts a low
input voltage into a higher output voltage. The basic configuration for a boost regulator is shown in Figure 31. In
continuous conduction mode (when the inductor current never reaches zero at steady state), the boost regulator
operates in two cycles. In the first cycle of operation, MOSFET Q is turned on and energy is stored in the
inductor. During this cycle, diode D is reverse biased and load current is supplied by the output capacitor, COUT.
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Typical Applications (continued)
Figure 31. Simplified Boost Converter Diagram
(a) First cycle of operation
(b) Second cycle of operation
In the second cycle, MOSFET Q is off and the diode is forward biased. The energy stored in the inductor is
transferred to the load and output capacitor. The ratio of these two cycles determines the output voltage. The
output voltage is defined as:
(6)
(ignoring the drop across the MOSFET and the diode), or
where
•
•
•
D is the duty cycle of the switch
VD is the forward voltage drop of the diode
VQ is the drop across the MOSFET when it is on
(7)
8.2.1.1 Design Requirements
To calculate component values for a Boost converter, the power supply parameters shown in Table 2 should be
known. The design shown in Figure 30 is the result of starting with example values shown in Table 2.
Table 2. Boost Design Parameters
18
DESIGN PARAMETER
EXAMPLE VALUE
Input voltage range
3V to 3.6V
Output voltage
5V
Maximum current
2A
Operating frequency
350kHz
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8.2.1.2 Detailed Design Procedure
8.2.1.2.1 Power Inductor Selection
The inductor is one of the two energy storage elements in a boost converter. Figure 32 shows how the inductor
current varies during a switching cycle. The current through an inductor is quantified as:
(8)
IL (A)
VIN
L
VIN VOUT
L
'iL
IL_AVG
t (s)
D*Ts
Ts
(a)
ID (A)
VIN - V OUT
L
ID_AVG
=IOUT_AVG
t (s)
D*Ts
Ts
(b)
ISW (A)
VIN
L
ISW_AVG
t (s)
D*Ts
Ts
(C)
Figure 32. A. Inductor Current B. Diode Current C. Switch Current
If VL(t) is constant, diL(t)/dt must be constant. Hence, for a given input voltage and output voltage, the current in
the inductor changes at a constant rate.
The important quantities in determining a proper inductance value are IL (the average inductor current) and ΔiL
(the inductor current ripple). If ΔiL is larger than IL, the inductor current will drop to zero for a portion of the cycle
and the converter will operate in discontinuous conduction mode. If ΔiL is smaller than IL, the inductor current will
stay above zero and the converter will operate in continuous conduction mode. All the analysis in this datasheet
assumes operation in continuous conduction mode. To operate in continuous conduction mode, the following
conditions must be met:
IL > ΔiL
(9)
(10)
(11)
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Choose the minimum IOUT to determine the minimum L. A common choice is to set ΔiL to 30% of IL. Choosing an
appropriate core size for the inductor involves calculating the average and peak currents expected through the
inductor. In a boost converter,
(12)
and IL_peak = IL(max) + ΔiL(max),
where
'iL = DVIN
2fSL
(13)
A core size with ratings higher than these values should be chosen. If the core is not properly rated, saturation
will dramatically reduce overall efficiency.
The LM3488 can be set to switch at very high frequencies. When the switching frequency is high, the converter
can be operated with very small inductor values. With a small inductor value, the peak inductor current can be
extremely higher than the output currents, especially under light load conditions.
The LM3488 senses the peak current through the switch. The peak current through the switch is the same as the
peak current calculated above.
8.2.1.2.2 Programming the Output Voltage
The output voltage can be programmed using a resistor divider between the output and the feedback pins, as
shown in Figure 33. The resistors are selected such that the voltage at the feedback pin is 1.26V. RF1 and RF2
can be selected using the equation,
RF1
VOUT = 1.26 1+
RF2
(14)
(
(
A 100-pF capacitor may be connected between the feedback and ground pins to reduce noise.
VIN
L
D
DR
VOUT
COUT
Q
LM3488
ISEN
FB
Rfb1
RSEN
Rfb2
Figure 33. Adjusting the Output Voltage
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8.2.1.2.3 Setting the Current Limit
The maximum amount of current that can be delivered to the load is set by the sense resistor, RSEN. Current limit
occurs when the voltage that is generated across the sense resistor equals the current sense threshold voltage,
VSENSE. When this threshold is reached, the switch will be turned off until the next cycle. Limits for VSENSE are
specified in Electrical Characteristics. VSENSE represents the maximum value of the internal control signal VCS.
This control signal, however, is not a constant value and changes over the course of a period as a result of the
internal compensation ramp (see Figure 20). Therefore the current limit threshold will also change. The actual
current limit threshold is a function of the sense voltage (VSENSE) and the internal compensation ramp:
RSEN x ISWLIMIT = VCSMAX = VSENSE - (D x VSL)
where
•
RSEN =
ISWLIMIT is the peak switch current limit, defined by the equation below. As duty cycle increases, the control
voltage is reduced as VSL ramps up. Since current limit threshold varies with duty cycle, the following equation
should be used to select RSEN and set the desired current limit threshold:
(15)
VSENSE - (D x VSL)
ISWLIMIT
(16)
The numerator of the above equation is VCS, and ISWLIMIT is calculated as:
ISWLIMIT =
(D x VIN)
IOUT
+
(1-D) (2 x fS x L)
(17)
To avoid false triggering, the current limit value should have some margin above the maximum operating value,
typically 120%. Values for both VSENSE and VSL are specified in Electrical Characteristics. However, calculating
with the limits of these two specs could result in an unrealistically wide current limit or RSEN range. Therefore, the
following equation is recommended, using the VSL ratio value given in Electrical Characteristics:
VSENSE - (D x VSENSE x VSLratio)
RSEN =
ISWLIMIT
(18)
RSEN is part of the current mode control loop and has some influence on control loop stability. Therefore, once
the current limit threshold is set, loop stability must be verified. To verify stability, use the following equation:
2 x VSL x fS x L
RSEN <
Vo - (2 x VIN)
(19)
If the selected RSEN is greater than this value, additional slope compensation must be added to ensure stability,
as described in Current Limit with External Slope Compensation.
8.2.1.2.4 Current Limit with External Slope Compensation
RSL is used to add additional slope compensation when required. It is not necessary in most designs and RSL
should be no larger than necessary. Select RSL according to the following equation:
RSEN x (Vo - 2VIN)
- VSL
2 x fS x L
RSL >
40 PA
where
•
RSEN is the selected value based on current limit. With RSL installed, the control signal includes additional
external slope to stabilize the loop, which will also have an effect on the current limit threshold. Therefore, the
current limit threshold must be re-verified, as illustrated in the equations below :
(20)
VCS = VSENSE – (D x (VSL + ΔVSL))
where
• ΔVSL is the additional slope compensation generated and calculated as:
ΔVSL = 40 µA x RSL
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(22)
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This changes the equation for current limit (or RSEN) to:
VSENSE - (D x(VSL + 'VSL))
ISWLIMIT =
RSEN
(23)
The RSEN and RSL values may have to be calculated iteratively in order to achieve both the desired current limit
and stable operation. In some designs RSL can also help to filter noise on the ISEN pin.
If the inductor is selected such that ripple current is the recommended 30% value, and the current limit threshold
is 120% of the maximum peak, a simpler method can be used to determine RSEN. The equation below will
provide optimum stability without RSL, provided that the above 2 conditions are met:
VSENSE
RSEN =
Vo - Vi
xD
ISWLIMIT +
L x fS
(24)
8.2.1.2.5 Power Diode Selection
Observation of the boost converter circuit shows that the average current through the diode is the average load
current, and the peak current through the diode is the peak current through the inductor. The diode should be
rated to handle more than its peak current. The peak diode current can be calculated using the formula:
ID(Peak) = IOUT/ (1−D) + ΔIL
(25)
In the above equation, IOUT is the output current and ΔIL has been defined in Figure 32.
The peak reverse voltage for boost converter is equal to the regulator output voltage. The diode must be capable
of handling this voltage. To improve efficiency, a low forward drop schottky diode is recommended.
8.2.1.2.6 Power MOSFET Selection
The drive pin of LM3488 must be connected to the gate of an external MOSFET. In a boost topology, the drain of
the external N-Channel MOSFET is connected to the inductor and the source is connected to the ground. The
drive pin (DR) voltage depends on the input voltage (see the Typical Characteristics section). In most
applications, a logic level MOSFET can be used. For very low input voltages, a sub-logic level MOSFET should
be used.
The selected MOSFET directly controls the efficiency. The critical parameters for selection of a MOSFET are:
1. Minimum threshold voltage, VTH(MIN)
2. On-resistance, RDS(ON)
3. Total gate charge, Qg
4. Reverse transfer capacitance, CRSS
5. Maximum drain to source voltage, VDS(MAX)
The off-state voltage of the MOSFET is approximately equal to the output voltage. VDS(MAX) of the MOSFET must
be greater than the output voltage. The power losses in the MOSFET can be categorized into conduction losses
and ac switching or transition losses. RDS(ON) is needed to estimate the conduction losses. The conduction loss,
PCOND, is the I2R loss across the MOSFET. The maximum conduction loss is given by:
where
•
DMAX is the maximum duty cycle.
(26)
(27)
The turn-on and turn-off transitions of a MOSFET require times of tens of nano-seconds. CRSS and Qg are
needed to estimate the large instantaneous power loss that occurs during these transitions.
The amount of gate current required to turn the MOSFET on can be calculated using the formula:
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IG = Qg.FS
(28)
The required gate drive power to turn the MOSFET on is equal to the switching frequency times the energy
required to deliver the charge to bring the gate charge voltage to VDR (see the Electrical Characteristics table and
the Typical Characteristics section for the drive voltage specification).
PDrive = FS.Qg.VDR
(29)
8.2.1.2.7 Input Capacitor Selection
Due to the presence of an inductor at the input of a boost converter, the input current waveform is continuous
and triangular, as shown in Figure 32. The inductor ensures that the input capacitor sees fairly low ripple
currents. However, as the input capacitor gets smaller, the input ripple goes up. The rms current in the input
capacitor is given by:
(30)
The input capacitor should be capable of handling the rms current. Although the input capacitor is not as critical
in a boost application, low values can cause impedance interactions. Therefore a good quality capacitor should
be chosen in the range of 10 µF to 20 µF. If a value lower than 10µF is used, then problems with impedance
interactions or switching noise can affect the LM3488. To improve performance, especially with VIN below 8 volts,
it is recommended to use a 20Ω resistor at the input to provide a RC filter. The resistor is placed in series with
the VIN pin with only a bypass capacitor attached to the VIN pin directly (see Figure 34). A 0.1-µF or 1-µF ceramic
capacitor is necessary in this configuration. The bulk input capacitor and inductor will connect on the other side
of the resistor with the input power supply.
RIN
VIN
CBYPASS
CIN
VIN
LM3488
Figure 34. Reducing IC Input Noise
8.2.1.2.8 Output Capacitor Selection
The output capacitor in a boost converter provides all the output current when the inductor is charging. As a
result it sees very large ripple currents. The output capacitor should be capable of handling the maximum rms
current. The rms current in the output capacitor is:
(31)
Where
(32)
and D, the duty cycle is equal to (VOUT − VIN)/VOUT.
The ESR and ESL of the output capacitor directly control the output ripple. Use capacitors with low ESR and ESL
at the output for high efficiency and low ripple voltage. Surface Mount tantalums, surface mount polymer
electrolytic and polymer tantalum, Sanyo- OSCON, or multi-layer ceramic capacitors are recommended at the
output.
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8.2.1.3 Application Curve
Figure 35. Typical Startup Waveform (horizontal scale: 10ms/DIV)
8.2.2 Designing SEPIC Using LM3488
Since the LM3488 controls a low-side N-Channel MOSFET, it can also be used in SEPIC (Single Ended Primary
Inductance Converter) applications. An example of SEPIC using LM3488 is shown in Figure 36. As shown in
Figure 36, the output voltage can be higher or lower than the input voltage. The SEPIC uses two inductors to
step-up or step-down the input voltage. The inductors L1 and L2 can be two discrete inductors or two windings of
a coupled transformer since equal voltages are applied across the inductor throughout the switching cycle. Using
two discrete inductors allows use of catalog magnetics, as opposed to a custom transformer. The input ripple can
be reduced along with size by using the coupled windings of transformer for L1 and L2.
Figure 36. Typical SEPIC Converter
Due to the presence of the inductor L1 at the input, the SEPIC inherits all the benefits of a boost converter. One
main advantage of SEPIC over boost converter is the inherent input to output isolation. The capacitor CS isolates
the input from the output and provides protection against shorted or malfunctioning load. Hence, the A SEPIC is
useful for replacing boost circuits when true shutdown is required. This means that the output voltage falls to 0V
when the switch is turned off. In a boost converter, the output can only fall to the input voltage minus a diode
drop.
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The duty cycle of a SEPIC is given by:
(33)
In the above equation, VQ is the on-state voltage of the MOSFET, Q, and VDIODE is the forward voltage drop of
the diode.
8.2.2.1 Design Requirements
To calculate component values for a SEPIC converter, the power supply parameters shown in Table 3 should be
known. The design shown in Figure 36 is the result of starting with example values shown in Table 3
Table 3. SEPIC Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Input voltage range
3 V to 24 V
Output voltage
5V
Maximum current
1A
Operating frequency
350 kHz
Max peak to peak output ripple
200 mV
8.2.2.2 Detailed Design Procedure
8.2.2.2.1 Power MOSFET Selection
As in boost converter, the parameters governing the selection of the MOSFET are the minimum threshold
voltage, VTH(MIN), the on-resistance, RDS(ON), the total gate charge, Qg, the reverse transfer capacitance, CRSS,
and the maximum drain to source voltage, VDS(MAX). The peak switch voltage in a SEPIC is given by:
VSW(PEAK) = VIN + VOUT + VDIODE
(34)
The selected MOSFET should satisfy the condition:
VDS(MAX) > VSW(PEAK)
(35)
The peak switch current is given by:
(36)
The rms current through the switch is given by:
(37)
8.2.2.2.2 Power Diode Selection
The Power diode must be selected to handle the peak current and the peak reverse voltage. In a SEPIC, the
diode peak current is the same as the switch peak current. The off-state voltage or peak reverse voltage of the
diode is VIN + VOUT. Similar to the boost converter, the average diode current is equal to the output current.
Schottky diodes are recommended.
8.2.2.2.3 Selection Of Inductors L1 and L2
Proper selection of the inductors L1 and L2 to maintain constant current mode requires calculations of the
following parameters.
Average current in the inductors:
(38)
(39)
IL2AVE = IOUT
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Peak to peak ripple current, to calculate core loss if necessary:
(40)
(41)
maintains the condition IL > ΔiL/2 to ensure constant current mode.
(VIN - VQ)(1-D)
L1 >
2IOUTfS
L2 >
(42)
(VIN - VQ)D
2IOUTfS
(43)
Peak current in the inductor, to ensure the inductor does not saturate:
(44)
(45)
IL1PK must be lower than the maximum current rating set by the current sense resistor.
The value of L1 can be increased above the minimum recommended to reduce input ripple and output ripple.
However, once DIL1 is less than 20% of IL1AVE, the benefit to output ripple is minimal.
By increasing the value of L2 above the minimum recommended, ΔIL2 can be reduced, which in turn will reduce
the output ripple voltage:
'VOUT =
(
IOUT
1-D
+
'IL2
2
)
ESR
where
•
ESR is the effective series resistance of the output capacitor.
(46)
If L1 and L2 are wound on the same core, then L1 = L2 = L. All the equations above will hold true if the
inductance is replaced by 2L. A good choice for transformer with equal turns is Coiltronics CTX series Octopack.
8.2.2.2.4 Sense Resistor Selection
The peak current through the switch, ISW(PEAK) can be adjusted using the current sense resistor, RSEN, to provide
a certain output current. Resistor RSEN can be selected using the formula:
VSENSE - D(VSL + 'VSL)
RSEN =
ISWPEAK
(47)
8.2.2.2.5 SEPIC Capacitor Selection
The selection of SEPIC capacitor, CS, depends on the rms current. The rms current of the SEPIC capacitor is
given by:
(48)
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The SEPIC capacitor must be rated for a large ACrms current relative to the output power. This property makes
the SEPIC much better suited to lower power applications where the rms current through the capacitor is
relatively small (relative to capacitor technology). The voltage rating of the SEPIC capacitor must be greater than
the maximum input voltage. Tantalum capacitors are the best choice for SMT, having high rms current ratings
relative to size. Ceramic capacitors could be used, but the low C values will tend to cause larger changes in
voltage across the capacitor due to the large currents. High C value ceramics are expensive. Electrolytics work
well for through hole applications where the size required to meet the rms current rating can be accommodated.
There is an energy balance between CS and L1, which can be used to determine the value of the capacitor. The
basic energy balance equation is:
(49)
Where
(50)
is the ripple voltage across the SEPIC capacitor, and
(51)
is the ripple current through the inductor L1. The energy balance equation can be solved to provide a minimum
value for CS:
(52)
8.2.2.2.6 Input Capacitor Selection
Similar to a boost converter, the SEPIC has an inductor at the input. Hence, the input current waveform is
continuous and triangular. The inductor ensures that the input capacitor sees fairly low ripple currents. However,
as the input capacitor gets smaller, the input ripple goes up. The rms current in the input capacitor is given by:
(53)
The input capacitor should be capable of handling the rms current. Although the input capacitor is not as critical
in a boost application, low values can cause impedance interactions. Therefore a good quality capacitor should
be chosen in the range of 10µF to 20µF. If a value lower than 10µF is used, then problems with impedance
interactions or switching noise can affect the LM3488. To improve performance, especially with VIN below 8 volts,
it is recommended to use a 20Ω resistor at the input to provide a RC filter. The resistor is placed in series with
the VIN pin with only a bypass capacitor attached to the VIN pin directly (see Figure 34). A 0.1µF or 1µF ceramic
capacitor is necessary in this configuration. The bulk input capacitor and inductor will connect on the other side
of the resistor with the input power supply.
8.2.2.2.7 Output Capacitor Selection
The ESR and ESL of the output capacitor directly control the output ripple. Use low capacitors with low ESR and
ESL at the output for high efficiency and low ripple voltage. Surface mount tantalums, surface mount polymer
electrolytic and polymer tantalum, Sanyo- OSCON, or multi-layer ceramic capacitors are recommended at the
output.
The output capacitor of the SEPIC sees very large ripple currents (similar to the output capacitor of a boost
converter. The rms current through the output capacitor is given by:
IRMS =
2
ISWPK2 - ISWPK ('IL1 + 'IL2)+ ('IL1 + 'IL2) (1-D) - IOUT2
3
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The ESR and ESL of the output capacitor directly control the output ripple. Use low capacitors with low ESR and
ESL at the output for high efficiency and low ripple voltage. Surface mount tantalums, surface mount polymer
electrolytic and polymer tantalum, Sanyo- OSCON, or multi-layer ceramic capacitors are recommended at the
output for low ripple.
9 Power Supply Recommendations
The LM3488 is designed to operate from various DC power supply including a car battery. If so, VIN input should
be protected from reversal voltage and voltage dump over 48 Volts. The impedance of the input supply rail
should be low enough that the input current transient does not cause drop below VIN UVLO level. If the input
supply is connected by using long wires, additional bulk capacitance may be required in addition to normal input
capacitor.
10 Layout
10.1 Layout Guidelines
Good board layout is critical for switching controllers such as the LM3488. First the ground plane area must be
sufficient for thermal dissipation purposes and second, appropriate guidelines must be followed to reduce the
effects of switching noise. Switch mode converters are very fast switching devices. In such devices, the rapid
increase of input current combined with the parasitic trace inductance generates unwanted Ldi/dt noise spikes.
The magnitude of this noise tends to increase as the output current increases. This parasitic spike noise may
turn into electromagnetic interference (EMI), and can also cause problems in device performance. Therefore,
care must be taken in layout to minimize the effect of this switching noise. The current sensing circuit in current
mode devices can be easily effected by switching noise. This noise can cause duty cycle jitter which leads to
increased spectral noise. The most important layout rule is to keep the AC current loops as small as possible.
Figure 37 shows the current flow of a boost converter. The top schematic shows a dotted line which represents
the current flow during onstate and the middle schematic shows the current flow during off-state. The bottom
schematic shows the currents we refer to as AC currents. They are the most critical ones since current is
changing in very short time periods. The dotted lined traces of the bottom schematic are the once to make as
short as possible.
Figure 37. Current Flow in a Boost Application
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Layout Guidelines (continued)
The PGND and AGND pins have to be connected to the same ground very close to the IC. To avoid ground loop
currents attach all the grounds of the system only at one point. A ceramic input capacitor should be connected as
close as possible to the Vin pin and grounded close to the GND pin. For a layout example please see AN-1204
LM378/LM3488 Evaluation Board (SNVA656A). For more information about layout in switch mode power
supplies please refer to AN-1229 SIMPLE SWITCHER® PCB Layout Guidelines (SNVA054c).
10.2 Layout Example
Output
Capacitors
Input
Capacitors
Output Diode
Current sense
trace changes
layers to allow
continuous
ground plane
Power FET
Sense Resistor
Output Inductor
Current
Sense Filter
Gate Resistor
To DR Pin
Compensation
To Input
VIN
Chip Power Filter
FA/SYNC/SD
DR
Set Frequency
PGND
ISEN
COMP
FB
AGND
Shutdown
LM3488
Set Output
Voltage
Tune Performance
To Output
Figure 38. Example Layout of a Boost Application using LM3488
11 Device and Documentation Support
11.1 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 4. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
LM3488
Click here
Click here
Click here
Click here
Click here
LM3488-Q1
Click here
Click here
Click here
Click here
Click here
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11.2 Trademarks
All trademarks are the property of their respective owners.
11.3 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.4 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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Product Folder Links: LM3488 LM3488-Q1
PACKAGE OPTION ADDENDUM
www.ti.com
8-Oct-2015
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
TBD
Call TI
Call TI
Op Temp (°C)
Device Marking
(4/5)
LM3488MM
ACTIVE
VSSOP
DGK
8
1000
S21B
LM3488MM/NOPB
ACTIVE
VSSOP
DGK
8
1000
Green (RoHS CU NIPDAUAG | CU SN Level-1-260C-UNLIM
& no Sb/Br)
-40 to 125
S21B
LM3488MMX/NOPB
ACTIVE
VSSOP
DGK
8
3500
Green (RoHS CU NIPDAUAG | CU SN Level-1-260C-UNLIM
& no Sb/Br)
-40 to 125
S21B
LM3488QMM/NOPB
ACTIVE
VSSOP
DGK
8
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
SSKB
LM3488QMMX/NOPB
ACTIVE
VSSOP
DGK
8
3500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
SSKB
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
8-Oct-2015
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
2-Sep-2015
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
LM3488MM
VSSOP
DGK
8
1000
178.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM3488MM/NOPB
VSSOP
DGK
8
1000
178.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM3488MMX/NOPB
VSSOP
DGK
8
3500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM3488QMM/NOPB
VSSOP
DGK
8
1000
178.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM3488QMMX/NOPB
VSSOP
DGK
8
3500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
2-Sep-2015
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM3488MM
VSSOP
DGK
8
1000
210.0
185.0
35.0
LM3488MM/NOPB
VSSOP
DGK
8
1000
210.0
185.0
35.0
LM3488MMX/NOPB
VSSOP
DGK
8
3500
367.0
367.0
35.0
LM3488QMM/NOPB
VSSOP
DGK
8
1000
210.0
185.0
35.0
LM3488QMMX/NOPB
VSSOP
DGK
8
3500
367.0
367.0
35.0
Pack Materials-Page 2
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