INTERSIL EL7535IY

EL7535
®
Data Sheet
August 16, 2005
FN7003.2
Monolithic 350mA Step-Down Regulator
Features
The EL7535 is a synchronous, integrated FET 350mA stepdown regulator in a MSOP10 package. The regulator is
internally compensated, which makes it possible to use just
five tiny external components to form a complete DC/DC
converter. The regulator operates with an input voltage
range from 2.5V to 6V, which accommodates supplies of
3.3V, 5V, or a Li-Ion battery source. The output can be
externally set from 0.8V to VIN with a resistive divider.
• Extremely small 350mA DC/DC converter
The EL7535 features PWM mode control. The operating
frequency is typically 1.4MHz. Additional features include
<1µA shut-down current, short-circuit protection, and overtemperature protection.
The EL7535 is available in the 10-pin MSOP package and is
specified for operation over the full -40°C to +85°C
temperature range.
Ordering Information
PART NUMBER
(BRAND)
• Max height 1.1mm MSOP10 package
• Possibly uses only five tiny external components with fixed
output
• Power-On-Reset output (POR)
• Internally-compensated voltage mode controller
• Up to 94% efficiency
• <1µA shut-down current
• Overcurrent and over-temperature protection
• Pb-Free plus anneal available (RoHS compliant)
Applications
• PDA and pocket PC computers
• Bar code readers
PACKAGE
TAPE &
REEL
PKG.
DWG. #
EL7535IY
(a)
10-Pin MSOP
-
MDP0043
EL7535IY-T7
(a)
10-Pin MSOP
7”
MDP0043
• Small form factor (SFP) modules
EL7535IY-T13
(a)
10-Pin MSOP
13”
MDP0043
Pinout and Typical Application Diagram
EL7535IYZ
(BAACA) (Note)
10-Pin MSOP
(Pb-free)
-
MDP0043
EL7535IYZ-T7
(BAACA) (Note)
10-Pin MSOP
(Pb-free)
7”
MDP0043
EL7535IYZ-T13
(BAACA) (Note)
10-Pin MSOP
(Pb-free)
13”
MDP0043
NOTE: Intersil Pb-free plus anneal products employ special Pb-free
material sets; molding compounds/die attach materials and 100%
matte tin plate termination finish, which are RoHS compliant and
compatible with both SnPb and Pb-free soldering operations. Intersil
Pb-free products are MSL classified at Pb-free peak reflow
temperatures that meet or exceed the Pb-free requirements of
IPC/JEDEC J STD-020.
• Cellular phones
• Portable test equipment
• Li-Ion battery powered devices
EL7535
(10-PIN MSOP)
TOP VIEW
C1
10µF
VO (1.8V@350mA)
C2
10µF
1.8µH
L1
1 SGND
FB 10
2 PGND
VO 9
3 LX
R1*
100kΩ
R2*
124kΩ
POR 8
4 VIN
EN 7
5 VDD
RSI 6
POR
EN
VIN (2.5V-6V)
R4
100kΩ
R5
100kΩ
RSI
R6
100kΩ
* FOR VARIABLE OUTPUT VOLTAGE: VO = 0.8V * (1 + R2 / R1)
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2004, 2005. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
EL7535
Absolute Maximum Ratings (TA = 25°C)
VIN, VDD, POR to SGND . . . . . . . . . . . . . . . . . . . . . . -0.3V to +6.5V
LX to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to (VIN + +0.3V)
RSI, EN, VO, FB to SGND . . . . . . . . . . . . . . . -0.3V to (VIN + +0.3V)
PGND to SGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +0.3V
Peak Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500mA
Operating Ambient Temperature . . . . . . . . . . . . . . . .-40°C to +85°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +145°C
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typ values are for information purposes only. Unless otherwise noted, all tests are
at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
Electrical Specifications
PARAMETER
VDD = VIN = VEN = 3.3V, C1 = C2 = 10µF, L = 1.8µH, VO = 1.8V, unless otherwise specified.
DESCRIPTION
CONDITIONS
MIN
TYP
MAX
UNIT
790
800
810
mV
250
nA
2.5
6
V
DC CHARACTERISTICS
VFB
Feedback Input Voltage
IFB
Feedback Input Current
VIN, VDD
Input Voltage
VIN,OFF
Minimum Voltage for Shutdown
VIN falling
2
2.2
V
VIN,ON
Maximum Voltage for Startup
VIN rising
2.2
2.4
V
IDD
Supply Current
PWM, VIN = VDD = 5V
400
500
µA
EN = 0, VIN = VDD = 5V
0.1
1
µA
PMOS FET Resistance
VDD = 5V, wafer test only
70
100
mΩ
RDS(ON)-NMOS NMOS FET Resistance
VDD = 5V, wafer test only
45
75
mΩ
RDS(ON)-PMOS
ILMAX
Current Limit
TOT,OFF
Over-temperature Threshold
TOT,ON
1.5
A
T rising
145
°C
Over-temperature Hysteresis
T falling
130
°C
IEN, IRSI
EN, RSI Current
VEN, VRSI = 0V and 3.3V
VEN1, VRSI1
EN, RSI Rising Threshold
VDD = 3.3V
VEN2, VRSI2
EN, RSI Falling Threshold
VDD = 3.3V
VPOR
Minimum VFB for POR, WRT Targeted
VFB Value
VFB rising
POR Voltage Drop
ISINK = 5mA
VOLPOR
VFB falling
-1
1
µA
2.4
V
0.8
V
95
%
86
%
35
70
mV
1.4
1.55
MHz
25
50
ns
AC CHARACTERISTICS
FPWM
PWM Switching Frequency
tRSI
Minimum RSI Pulse Width
tSS
Soft-start Time
tPOR
Power On Reset Delay Time
1.25
Guaranteed by design
650
2
80
100
µs
120
ms
FN7003.2
August 16, 2005
EL7535
Pin Descriptions
PIN NUMBER
PIN NAME
PIN FUNCTION
1
SGND
Negative supply for the controller stage
2
PGND
Negative supply for the power stage
3
LX
Inductor drive pin; high current digital output with average voltage equal to the regulator output voltage
4
VIN
Positive supply for the power stage
5
VDD
Power supply for the controller stage
6
RSI
Resets POR timer
7
EN
Enable
8
POR
9
VO
Output voltage sense
10
FB
Voltage feedback input; connected to an external resistor divider between VO and SGND for variable
output
Power on reset open drain output
Timing Diagram
VO
MIN
25ns
RSI
100ms
100ms
POR
3
FN7003.2
August 16, 2005
EL7535
Block Diagram
VDD
VO
+
-
10pF
124K
FB
CURRENT
LIMIT
5M
+
PWM
COMPENSATION
100K
CLOCK
1.4MHz
VIN
+
PWM
COMPARATOR
P-DRIVER
LX
CONTROL
LOGIC
RAMP
GENERATOR
1.8µ
1.8V
350mA
EN
EN
SOFTSTART
10µF
10µF
N-DRIVER
5V
+
–
BANDGAP
REFERENCE
UNDERVOLTAGE
LOCKOUT
PGND
100K
TEMPERATURE
SENSE
SGND
POR
PG
POR
RSI
4
FN7003.2
August 16, 2005
EL7535
Typical Performance Curves
100
100
VIN=5V
VIN=3.3V
VO=3.3V
95
90
EFFICIENCY (%)
90
EFFICIENCY (%)
VO=2.5V
95
85
80
VO=2.5V
VO=1.8V
75
VO=1.2V
70
85
VO=1.8V
80
75
VO=1V
70
65
65
60
60
100
0
300
200
400
100
0
200
IO (mA)
JEDEC JESD51-7 HIGH EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD
1 1.087W
θ
M
JA
=
0.8
SO
11
0.6
5°
P8
C/
/1
0
W
0.4
0.2
0
0
25
75 85 100
50
400
FIGURE 2. EFFICIENCY
0.7
POWER DISSIPATION (W)
1.2
300
IO (mA)
FIGURE 1. EFFICIENCY
POWER DISSIPATION (W)
VO=1.2V
125
150
AMBIENT TEMPERATURE (°C)
JEDEC JESD51-3 LOW EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD
0.6
607mW
θ
0.5
M
JA
=
0.4
SO
P8
/1
0
6°
C/
W
20
0.3
0.2
0.1
0
0
25
50
75 85 100
125
150
AMBIENT TEMPERATURE (°C)
FIGURE 3. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
FIGURE 4. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
Waveforms
All waveforms are taken at VIN=3.3V, VO=1.8V, IO=350mA with component values shown on page 1, unless otherwise noted
VIN
(2V/DIV)
VIN
(1V/DIV)
VO
(2V/DIV)
IIN
(0.2A/DIV)
POR
(2V/DIV)
VO
(1V/DIV)
0.5ms/DIV
FIGURE 5. START-UP 1
5
50ms/DIV
FIGURE 6. START-UP 2
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August 16, 2005
EL7535
Waveforms
(Continued)
All waveforms are taken at VIN=3.3V, VO=1.8V, IO=350mA with component values shown on page 1, unless otherwise noted
VIN
(2V/DIV)
VO
(2V/DIV)
350mA
100mA
IO
RSI
(2V/DIV)
∆VO
20mV/DIV
POR
(2V/DIV)
0.2ms/DIV
50ms/DIV
FIGURE 8. TRANSIENT RESPONSE
FIGURE 7. POR FUNCTION
∆VIN
100mV/DIV
0.5A/DIV
iL
VLX
2V/DIV
∆VO
10mV/DIV
1µs/DIV
FIGURE 9. STEADY-STATE
Applications Information
Product Description
The EL7535 is a synchronous, integrated FET 350mA stepdown regulator which operates from an input of 2.5V to 6V.
The output voltage is user-adjustable with a pair of external
resistors.
The internally-compensated controller makes it possible to
use only two ceramic capacitors and one inductor to form a
complete, very small footprint 350mA DC/DC converter.
PWM Operation
In the PWM mode, the P channel MOSFET and N channel
MOSFET always operate complementary. When the
PMOSFET is on and the NMOSFET off, the inductor current
increases linearly. The input energy is transferred to the
output and also stored in the inductor. When the P channel
MOSFET is off and the N channel MOSFET on, the inductor
6
current decreases linearly, and energy is transferred from
the inductor to the output. Hence, the average current
through the inductor is the output current. Since the inductor
and the output capacitor act as a low pass filter, the duty
cycle ratio is approximately equal to VO divided by VIN.
The output LC filter has a second order effect. To maintain
the stability of the converter, the overall controller must be
compensated. This is done with the fixed internally
compensated error amplifier and the PWM compensator.
Because the compensations are fixed, the values of input
and output capacitors are 10µF to 22µF ceramic. The
inductor is nominally 1.8µH, though 1.5µA to 2.2µH can be
used.
Start-Up and Shut-Down
When the EN pin is tied to VIN, and VIN reaches
approximately 2.4V, the regulator begins to switch. The
FN7003.2
August 16, 2005
EL7535
output voltage is gradually increased to ensure proper softstart operation.
When the EN pin is connected to a logic low, the EL7535 is
in the shut-down mode. All the control circuitry and both
MOSFETs are off, and VOUT falls to zero. In this mode, the
total input current is less than 1µA.
When the EN reaches logic HI, the regulator repeats the
start-up procedure, including the soft-start function.
RSI/POR Function
When powering up, the open-collector Power-On-Reset
output holds low for about 100ms after VO reaches the
preset voltage. When the active-HI reset signal RSI is
issued, POR goes to low immediately and holds for the
same period of time after RSI comes back to LOW. The
output voltage is unaffected. (Please refer to the timing
diagram). When the function is not used, connect RSI to
ground and leave open the pull-up resister R4 at POR pin.
The POR output also serves as a 100ms delayed Power
Good signal when the pull-up resister R4 is installed. The
RSI pin needs to be directly (or indirectly through a resister
R6) connected to Ground for this to function properly.
Output Voltage Selection
Users can set the output voltage of the converter with a
resister divider, which can be chosen based on the following
formula:
R 

V O = 0.8 ×  1 + ------2-
R 1

The inductor must be able to handle IO for the RMS load
current, and to assure that the inductor is reliable, it must
handle the 1.5A surge current that can occur during a
current limit condition.
Current Limit and Short-Circuit Protection
The current limit is set at about 1.5A for the PMOS. When a
short-circuit occurs in the load, the preset current limit
restricts the amount of current available to the output, which
causes the output voltage to drop below the preset voltage.
In the meantime, the excessive current heats up the
regulator until it reaches the thermal shut-down point.
Thermal Shut-Down
Once the junction reaches about 145°C, the regulator shuts
down. Both the P channel and the N channel MOSFETs turn
off. The output voltage will drop to zero. With the output
MOSFETs turned off, the regulator will soon cool down.
Once the junction temperature drops to about 130°C, the
regulator will restart again in the same manner as EN pin
connects to logic HI.
Thermal Performance
The EL7535 is in a fused-lead MSOP10 package. Compared
with regular MSOP10 package, the fused-lead package
provides lower thermal resistance. The θJA is 100°C/W on a
4-layer board and 125°C/W on 2-layer board. Maximizing the
copper area around the pins will further improve the thermal
performance.
Layout Considerations
Component Selection
Because of the fixed internal compensation, the component
choice is relatively narrow. For a regulator with fixed output
voltage, only two capacitors and one inductor are required.
We recommend 10µF to 22µF multi-layer ceramic capacitors
with X5R or X7R rating for both the input and output
capacitors, and 1.5µH to 2.2µH inductance for the inductor.
The RMS current present at the input capacitor is decided by
the following formula:
V IN × ( V IN - V O )
I INRMS = ------------------------------------------------- × I O
V IN
This is about half of the output current IO for all the VO. This
input capacitor must be able to handle this current.
The inductor peak-to-peak ripple current is given as:
The layout is very important for the converter to function
properly. The following PC layout guidelines should be
followed:
• Separate the Power Ground ( ) and Signal Ground ( );
connect them only at one point right at the pins
• Place the input capacitor as close to VIN and PGND pins
as possible
• Make the following PC traces as small as possible:
- from LX pin to L
- from CO to PGND
• If used, connect the trace from the FB pin to R1 and R2 as
close as possible
• Maximize the copper area around the PGND pin
• Place several via holes under the chip to additional ground
plane to improve heat dissipation
The demo board is a good example of layout based on this
outline. Please refer to the EL7535 Application Brief.
( V IN - V O ) × V O
∆I IL = ------------------------------------------L × V IN × f S
• L is the inductance
• fS the switching frequency (nominally 1.4MHz)
7
FN7003.2
August 16, 2005
EL7535
Package Outline Drawing
NOTE: The package drawing shown here may not be the latest version. To check the latest revision, please refer to the Intersil
website at <http://www.intersil.com/design/packages/index.asp>
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
8
FN7003.2
August 16, 2005