ENPIRION EN5336QI 3a voltage mode synchronous buck pwm dc-dc converter with integrated inductor external feedback output voltage programming Datasheet

EN5336QI
3A Voltage Mode Synchronous Buck PWM
DC-DC Converter with Integrated Inductor
External Feedback Output Voltage Programming
Description
Features
The EN5336QI is a Power System on Silicon DCDC converter. It is specifically designed to meet
the precise voltage and fast transient
requirements of present and future highperformance, low-power processor, DSP, FPGA,
memory boards and system level applications in
a distributed power architecture. Advanced circuit
techniques, ultra high switching frequency, and
very advanced, high-density, integrated circuit
and proprietary inductor technology deliver highquality, ultra compact, non-isolated DC-DC
conversion. Operating this converter requires
only small value input and output ceramic
capacitors, a soft-start capacitor and a resistor
divider for voltage feedback to set the output
voltage to the desired value.
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The Enpirion solution significantly helps in
system design and productivity by offering greatly
simplified
board
design,
layout
and
manufacturing requirements. In addition, a
reduction in the number of vendors required for
the complete power solution helps to enable an
overall system cost savings.
Applications
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All Enpirion products are RoHS compliant and
lead-free manufacturing environment compatible.
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Typical Application Circuit
VIN
PVIN
POK
VOUT
Point of load regulation for low-power
processors, network processors, DSPs,
FPGAs, and ASICs
Notebook computers, servers, workstations
Broadband, networking, LAN/WAN, optical
Low voltage, distributed power architectures
with 2.5V, 3.3V or 5V rails
DSL, STB, DVR, DTV, iPC
Ripple sensitive applications
VOUT
Ordering Information
AVIN
22µF
XOV
SS
15 nF
Integrated INDUCTOR, MOSFETS, Controller
Footprint 1/3rd that of competing solutions.
Minimum external components.
Up to 10W continuous output power.
5MHz operating frequency.
High efficiency, up to 93%.
VOUT accuracy 3% over line, load and temp.
Wide input voltage range of 2.375V to 5.5V.
External resistor divider for voltage feedback
and output voltage selection.
Output enable pin and Power OK signal.
Programmable soft-start time.
Programmable over-current protection.
Thermal shutdown, short circuit, and UVLO
RoHS compliant, MSL level 3, 260C reflow.
47µF
XFB
AGND
PGND
Part Number
EN5336QI-T
EN5336QI-E
Temp Rating
(°C)
Package
-40 to +85
44-pin QFN T&R
QFN Evaluation Board
Figure 1. Simple Layout.
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EN5336QI
Rev 1.2 October 2008
Pin Configuration
Below is a top view diagram of the EN5336QI package.
NOTE: NC pins are not to be electrically connected to each other or to any external signal, ground, or
voltage. However, they must be soldered to the PCB. Failure to follow this guideline may result in
part malfunction or damage.
Figure 2. Pin-out diagram, top view.
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EN5336QI
Rev 1.2 October 2008
Pin Descriptions
PIN
NAME
1-3
NC
4-6
NC(SW)
7
NC
8-14
VOUT
15
NC(SW)
16
NC
17-20
PGND
21-24
PVIN
25-26
NC
27
ROCP
28
AVIN
29
30-31
32
33
34
AGND
NC
XFB
XOV
NC
35
POK
36
NC
37
SS
38
39
EAIN
EAOUT
40
COMP
41
ENABLE
42-44
NC
FUNCTION
NO CONNECT – Do not electrically connect these pins to each other or to
PCB.
No Connect. These pins are internally connected to the switch node of the
internal MOSFETs. NC(SW) pins are not to be electrically connected to any
external signal, ground, or voltage.
No connect – Do not electrically connect these pins to each other or to PCB.
Regulated converter output. Connect these pins to the load and place output
capacitor from these pins the PGND pins 17-18
No Connect. These pins are internally connected to the switch node of the
internal MOSFETs. NC(SW) pins are not to be electrically connected to any
external signal, ground, or voltage.
No connect – Do not electrically connect these pins to each other or to PCB.
Output power ground. Connect these pins to the ground electrode of the
output filter capacitors. Refer to layout guideline section.
Input power supply. Connect to input power supply. Decouple with input
capacitor to PGND (pins 19-20).
No connect – Do not electrically connect these pins to each other or to PCB.
Optional Over Current Protection adjust pin. Place ROCP resistor between
this pin and AGND (pin 40) to increase the over current trip point by 50%.
Analog voltage input for the controller circuits. Connect this pin to the input
power supply.
Analog ground for the controller circuits.
No connect – Do not electrically connect these pins to each other or to PCB.
Voltage Feedback pin for external voltage divider network.
Optional Over-Voltage Programming Feedback pin.
No connect – Do not electrically connect these pins to each other or to PCB.
Power OK is an open drain transistor for power system state indication. POK
is a logic high when VOUT is with -10% to +20% of VOUT nominal.
No connect – Do not electrically connect these pins to each other or to PCB.
Soft-Start node. The soft-start capacitor is connected between this pin and
AGND. The value of this resistor determines the startup timing.
Optional Error Amplifier input. Allows for customization of the control loop.
Optional Error Amplifier output. Allows for customization of the control loop.
Optional Error Amplifier Buffer output. Allows for customization of the control
loop.
Input Enable. Applying a logic high, enables the output and initiates a softstart. Applying a logic low disables the output.
No connect – Do not electrically connect these pins to each other or to PCB.
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EN5336QI
Rev 1.2 October 2008
Block Diagram
POK
PVIN
power
Good
Logic
UVLO
Thermal Limit
ROCP
Current Limit
XOV
Over
Voltage
VOUT
Over Voltage
P-Drive
VOUT
(-)
N-Drive
PWM
Comp
(+)
PGND
Compensation
Network
Sawtooth
Generator
Voltage
Selector
(-)
Error
Amp
(+)
ENABLE
SS
XFB
Reference
Voltage
selector
Soft Start
Bandgap
Reference
COMP
EAIN
EAOUT
Figure 3. System block diagram.
Absolute Maximum Ratings
CAUTION: Absolute Maximum ratings are stress ratings only. Functional operation beyond
recommended operating conditions is not implied. Stress beyond Absolute maximum ratings may
cause permanent damage to the device. Exposure to absolute maximum rated conditions for
extended periods may affect device reliability.
Maximum Electrical Ratings
Min
Voltages on: VIN, VOUT
Voltages on XFB
Voltages on: ENABLE
Max
-0.3V
-0.3V
-0.3V
7.0V
2.5V
VIN + 0.3V
-40°C
-65°C
+85°C
+150°C
+260°C
Maximum Thermal Ratings
Ambient operating range
Storage Temperature Range
Reflow Peak Body Temperature MSL3 (10 Sec)
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EN5336QI
Rev 1.2 October 2008
Recommended Operating Conditions
PARAMETER
Input Voltage Range
EN5336QI Operating Ambient Temperature
EN5336QI Operating Ambient Temperature
Operating Junction Temperature
SYMBOL
VIN
TA
TA
TJ
MIN
2.375
0
-40
-40
MAX
5.5
+70
+85
+125
UNITS
V
°C
°C
°C
Thermal Characteristics
SYMBOL
PARAMETER
TYP
UNITS
Thermal Shutdown
TSD
150
°C
Thermal Shutdown Hysteresis
TSDH
15
°C
Thermal Resistance: Junction to Case (0 LFM) (Note 1)
3
°C/W
θJC
Thermal Resistance: Junction to Ambient (0 LFM)
25
°C/W
θJA
Note 1: Based on a four-layer board and proper thermal design in line with JEDEC EIJ/JESD 51 Standards.
Electrical Characteristics
NOTE: VIN=5.5V over operating temperature range unless otherwise noted. Typical values are at TA =
25°C.
PARAMETER
Operating Input
Voltage
Feedback Pin Voltage
Drop out voltage
Shut-Down Supply
Current
Switching Frequency
SYMBOL
TEST CONDITIONS
VIN
VFB
VIN - VOUT
IS
MIN
TYP
2.375
MAX
UNITS
5.5
V
600
V
mV
0.75
Drop out voltage at full load
ENABLE=0V
FOSC
100
µA
5
MHz
VOUT
Output Voltage
Regulation
VOUT
Over line, load and temperature
-3.0
3.0
%
Maximum Continuous Output Current
Over Current Trip
Piont
IOCP
4.5
A
Enable Operation
Disable Threshold
VDISABLE
Enable Threshold
VENABLE
Enable Pin Current
IENABLE
Max voltage to ensure the converter is
disabled
2.375V ≤ VIN ≤ 5.5V
5.5V < VIN
VIN = 5.5V
0.8
1.8
2.0
V
V
µA
50
Voltage Select Operation
VSX Logic Low
Threshold
VSX-Low
Threshold voltage for Logic Low
VSX Logic High
Threshold
VSX-High
Threshold voltage for Logic High
(internally pulled high; can be left
floating to achieve logic high)
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1.8
0.8
V
VIN
V
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EN5336QI
Rev 1.2 October 2008
PARAMETER
SYMBOL
VSX Pin Current
IVSX
TEST CONDITIONS
(VIN = 5.5V)
VSx = GND
VSx = VIN
VSx = Open
MIN
TYP
MAX
50
0
0
UNITS
µA
Power OK Operation
POK low voltage
Max POK Voltage
VPOK
VPOK
IPOK = 4mA (sink current)
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0.4
VIN
6
V
V
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EN5336QI
Rev 1.2 October 2008
Typical Performance Characteristics
VIN=5.0V
VIN=3.3V
95
90
Efficiency (%)
80
V OUT = 1.8V
75
V OUT = 1.5V
70
V OUT = 1.2V
65
Efficiency (%)
V OUT = 2.5V
85
90
VOUT = 2.5V
85
VOUT = 1.8V
80
VOUT = 1.5V
75
VOUT = 1.2V
70
VOUT = 0.8V
65
60
60
55
55
50
50
0.1
95
V OUT = 3.3V
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
2.1
2.3
2.5
2.7
2.9
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9
Lo a d C urre nt ( A )
Lo a d C urre nt ( A )
Efficiency versus Load, VIN = 5.0V
Efficiency versus Load, VIN = 3.3V
Load transient, 0 – 3A, VIN/VOUT = 5.5V/1.2V
Load transient, 0 – 3A, VIN/VOUT = 5.5V/3.3V
Start-up waveform, VIN/VOUT = 5.5V/1.2V
Shut-down waveform, VIN/VOUT = 5.5V/1.2V
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EN5336QI
Rev 1.2 October 2008
Theory of Operation
voltage:
Synchronous Buck Converter
Ra1 =
The EN5336QI is a synchronous, pin
programmable power supply with integrated
power MOSFET switches and integrated
inductor. The nominal input voltage range is 2.45.0V. The output can be set to any voltage
between 0.75V and VIN – 600mV. The feedback
control loop is a type III voltage-mode and the
part uses a low-noise PWM topology. Up to 3A of
output current can be drawn from this converter.
The 5MHz operating frequency enables the use
of small-size output capacitors.
The power supply has the following protection
features:
• Over-current protection (to protect the IC
from excessive load current)
• Thermal shutdown with hysteresis
• Over-voltage protection
• Under-voltage lockout circuit to disable the
converter output when the input voltage is
less than approximately 2.2V
(Vout − 0.75V ) * Rb1
0.75V
If over-voltage protection is desired, use the
following equation to set the resistor Ra2 for the
desired OVP trip-point:
Ra 2 =
(OVPtrip − 0.90V ) * Rb 2
0.90V
By design, if both resistor dividers are the same,
the OV trip-point will be 20% above the nominal
output voltage.
VIN
PVIN
22µF
POK
VOUT
VOUT
AVIN
Ra2
Ra1
XOV
SS
CSS
47µF
XFB
AGND
Rb2
PGND
Rb1
Figure 4. VOUT and OVP resistor divider networks.
Additional features include:
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Soft-start circuit, limiting the in-rush
current when the converter is powered up
Power good circuit indicating whether the
output voltage is within 90% - 120% of the
programmed voltage
Output Voltage Programming
The EN5336QI output voltage is programmed
using a simple resistor divider network. Figure 4
shows the resistor divider configuration.
The EN5336QI output voltage and over voltage
thresholds are determined by the voltages
presented at the XFB and XOV pins respectively.
These voltages are set by way of resistor dividers
between VOUT and AGND with the midpoint going
to XFB and XOV.
NOTE: if no OVP divider is present, there will be
no over-voltage protection and POK will remain
“high” as long as VOUT remains above 90% of the
nominal VOUT setting.
Input Capacitor Selection
The EN5336QI requires about 20uF of input
capacitance.
Low-cost,
low-ESR
ceramic
capacitors should be used as input capacitors for
this converter. The dielectric must be X5R or
X7R rated. In some applications, lower value
capacitors are needed in parallel with the larger,
capacitors in order to provide high frequency
decoupling. It is recommended to use 10V rated
MLCC capacitors. Table 2 lists some
recommended part numbers for input capacitors.
It is recommended that Rb1 and Rb2 resistor
values be ~2kΩ. Use the following equation to
set the resistor Ra1 for the desired output
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EN5336QI
Rev 1.2 October 2008
Table 2. Recommended input capacitors.
Description
10uF, 10V, 10%
X7R, 1206
(2 capacitors needed)
22uF, 10V, 10%
X5R, 1210
(1 capacitor needed)
MFG
P/N
Murata
GRM31CR71A106KA01L
Taiyo Yuden
Murata
LMK316B7106KL-T
GRM32ER71A226KE20L
Taiyo Yuden
LMK325B7226KM-T
Output Capacitor Selection
The EN5336QI has been optimized for use with
approximately 50µF of output capacitance. Low
ESR ceramic capacitors are required with X5R or
X7R rated dielectric formulation.
Y5V or
equivalent dielectric formulations must not be
used as these lose capacitance with frequency,
temperature and bias voltage.
Output ripple voltage is determined by the
aggregate output capacitor impedance. Output
impedance, denoted as Z, is comprised of
effective series resistance, ESR, and effective
series inductance, ESL:
Z = ESR + ESL.
Placing output capacitors in parallel reduces the
impedance and will hence result in lower ripple
voltage.
1
Z Total
=
1
1
1
+
+ ... +
Z1 Z 2
Zn
Typical ripple versus capacitance is given below:
Output Capacitor
Configuration
1 x 47 uF
3 x 22 uF
Typical Output Ripple (mVp-p)
(as measured on EN5336QI
Evaluation Board)
30
15
Table 3. Recommended output capacitors.
Description
MFG
P/N
22uF, 6.3V, 10%
X5R, 1206
(3 capacitors needed)
47uF, 10V, 10%
X5R, 1210
47uF, 6.3V, 10%
X5R, 1210
(1 capacitor needed)
Murata
GRM31CR60J226KE19L
Taiyo Yuden
JMK316BJ226KL-T
Murata
GRM32ER61A476KE20L
AVX
12106D476KAT2
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Enable Operation
The ENABLE pin provides a means to shut down
the device, or enable normal operation. A logic
high will enable the converter into normal
operation. When the ENABLE pin is asserted,
the device will undergo a normal soft start. A
logic low will disable the converter and cause it to
shut down. When Enable goes low, circuitry
internal to the device continue to operate to
ensure the output voltage is gradually returned to
zero and the circuits turn off subsequently. A
short low going pulse on Enable is ignored.
Soft-Start Operation
Soft start is a method to reduce in-rush current
when the device is enabled. The output voltage
is ramped up slowly upon start-up. The output
rise time is controlled by choice of a soft-start
capacitor, which is placed between the SS pin
(pin 37) and the AGND pin (pin 29).
Rise Time: TR = Css* 75KΩ
During start-up of the converter, the reference
voltage to the error amplifier is gradually
increased from zero to its final level by an
internal current source of typically 10uA. Typical
soft-start rise time is 1mS to 3mS. The rise time
is measured from the time when AVIN > VUVLO
and the Enable signal crosses its logic high
threshold. Typical SS capacitor values are in the
range of 15nF to 50 nF.
Power-up Sequencing
The sequencing of AVIN, PVIN and ENABLE
should meet the following requirements:
1. ENABLE should not be asserted before PVIN.
2. PVIN should not be applied before AVIN.
Note that tying AVIN, PVIN and ENABLE
together and brought up at the same time does
meet these requirements.
POK Operation
The POK signal is an open drain signal from the
converter indicating the output voltage is within
the specified range. The POK signal will be a
logic high when the output voltage is above 90%
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EN5336QI
Rev 1.2 October 2008
of VOUT and below the user programmed OVP
trip-point. If the output voltage goes outside of
this range, the POK signal will be a logic low until
the output voltage has returned to within this
range. In the event of an over-voltage condition
the POK signal will go low and will remain in this
condition until the output voltage has dropped to
95% of the programmed output voltage before
returning to the high state.
NOTE: If no over voltage protection is used, POK
will remain “high” as long as VOUT remains above
90% of the nominal VOUT setting.
stops, the lower N-MOSFET is turned on and the
POK signal goes low. When the output voltage
drops below 95% of the programmed output
voltage, normal PWM operation resumes and
POK returns to its high state.
Thermal Overload Protection
Thermal shutdown will disable operation once
the Junction temperature exceeds approximately
150ºC. Once the junction temperature drops by
approx 25ºC, the converter will re-start with a
normal soft-start.
Over-Current Protection
Input Under-voltage Lock-out
The current limit function is achieved by sensing
the current flowing through the sense PMOSFET. When the sensed current exceeds the
current limit, both NFET and PFET switches are
turned off. If the over-current condition is
removed, the over-current protection circuit will
enable the PWM operation. This circuit is
designed to provide high noise immunity.
Circuitry is provided to ensure that when the
input voltage is below the specified voltage
range, the converter will not start-up. Circuits for
hysteresis, input de-glitch and output leading
edge blanking are included to ensure high noise
immunity and prevent false tripping.
The nominal over current trip point is set to 4.5A.
It is possible to increase the over-current set
point by about 50% by connecting a 7.5kΩ
resistor between ROCP (pin 27) and GND. The
typical voltage at the ROCP pin is 0.75V.
In some cases, such as the start-up of FPGA
devices, it is desirable to blank the over-current
protection feature. In order to disable overcurrent protection, the ROCP pin should be tied
to any voltage between 2.5V and PVIN.
Over-Voltage Protection
Compensation
The EN5336QI is internally compensated
through the use of a type 3 compensation
network and is optimized for use with about 50uF
of output capacitance and will provide excellent
loop bandwidth and transient performance for
most applications. (See the section on Capacitor
Selection for details on recommended capacitor
types.) Voltage mode operation provides high
noise immunity at light load.
In some cases modifications to the compensation
may be required. For more information, contact
Enpirion Applications Engineering support.
When the output voltage exceeds 120% of the
programmed output voltage, the PWM operation
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EN5336QI
Rev 1.2 October 2008
Design Considerations for Lead-Frame Based Modules
Exposed Metal on Bottom of Package
Lead frame offers many advantages in thermal performance, in reduced electrical lead resistance,
and in overall foot print. However, they do require some special considerations.
In the assembly process lead frame construction requires that, for mechanical support, some of the
lead-frame cantilevers be exposed at the point where wire-bond or internal passives are attached.
This results in several small pads being exposed on the bottom of the package.
Only the large thermal pad and the perimeter pads are to be mechanically or electrically connected to
the PC board. The PCB top layer under the EN5336QI should be clear of any metal except for the
large thermal pad. The “grayed-out” area in Figure 5 represents the area that should be clear of any
metal (traces, vias, or planes), on the top layer of the PCB. Figure 6 shows the recommended PCB
footprint for this device.
Figure 5. Lead-Frame exposed metal. Grey area highlights exposed metal that is not to be mechanically or
electrically connected to the PCB.
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EN5336QI
Rev 1.2 October 2008
Figure 6. Recommended PCB footprint.
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EN5336QI
Rev 1.2 October 2008
Package Dimensions
Figure 7. Package dimensions.
Contact Information
Enpirion, Inc.
685 Route 202/206
Suite 305
Bridgewater, NJ 08807
Phone: 908-575-7550
Fax: 908-575-0775
Enpirion reserves the right to make changes in circuit design and/or specifications at any time without notice. Information furnished by Enpirion is
believed to be accurate and reliable. Enpirion assumes no responsibility for its use or for infringement of patents or other third party rights, which may
result from its use. Enpirion products are not authorized for use in nuclear control systems, as critical components in life support systems or equipment
used in hazardous environment without the express written authority from Enpirion.
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