AMS AS1335 Datasheet
Annonce
Annonce
austriamicrosystems AG is now ams AG
The technical content of this austriamicrosystems datasheet is still valid.
Contact information:
Headquarters:
ams AG
Tobelbaderstrasse 30
8141 Unterpremstaetten, Austria
Tel: +43 (0) 3136 500 0 e-Mail: [email protected]
Please visit our website at
www.ams.com
D a ta s h e e t
A S 1 3 3 5
1 . 5 A , 1 . 5 M H z , S y n c h r o n o u s D C / D C St e p - D o w n C o n v e r t e r
1 General Description
The AS1335 is a high-efficiency, constant-frequency synchronous buck converter available in a fixed or an adjustable output voltage version. The wide input voltage range (2.6V to 5.25V), the high output current (up to
1.5A) and minimal external component requirements make the AS1335 perfect for any single Li-Ion batterypowered application.
Typical supply current with no load is 400µA and decreases to
≤
1µA in shutdown mode. The highly efficient duty cycle (100%) provides low dropout operation, prolonging battery life in portable systems.
The device also offers a power-ok signal with a 215ms delay, which can be reseted or delayed further via the
RSI pin.
An internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. The internally fixed switching frequency (1.5MHz) allows for the use of small surface mount external components.
The AS1335 is available in a 10-pin TDFN 3x3mm package.
2 Key Features
! High Efficiency: Up to 96%
!
Output Current: 1.5A
! Input Voltage Range: 2.6V to 5.25V
!
Output Voltage Range: 0.6V to V
IN
! Constant Frequency Operation: 1.5MHz
!
No Schottky Diode Required
! Power OK with 215ms delay
!
Low Dropout Operation: 100% Duty Cycle
! Low Quiescent Supply Current: 400µA
!
!
still valid
! Thermal Protection
!
10-pin TDFN 3x3mm Package
ams
3 Applications
tion with low power-consumption requirements.
Figure 1. AS1335 - Typical Application Diagram
V
IN
2.6V to 5.25V
VIN
C
IN
22µF
NC
Technical
AS1335
GND
SW
PGND
GND
2.2µH
FB
RSI
C
OUT
22µF
V
OUT
1.0V, 1.5A
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AS1335
Datasheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
VIN 1 10 SW
NC 2 9 PGND
Pin Descriptions
Table 1. Pin Descriptions
Pin
Number
1
2
3
4
5
6
Pin Name
VIN
NC
EN
POK
GND
RSI
AS1335
EN 3 8 GND
POK
GND
4
5
11
7 FB
6 RSI
Positive Supply Voltage
ceramic capacitor.
Not Connected.
Description AG still
≥
22µF
Enable Input
. Driving this pin above 1.4V enables the device. Driving this pin below 0.3V puts the device in shutdown mode. In shutdown mode all functions are disabled, drawing
≤
1µA supply current.
Note:
This pin should not be left floating.
not used.
ams
Ω
pull-up resistor to V
OUT
or pin VIN for logic levels. Leave this pin unconnected if the Power-OK feature is
LOW Signal: Out of regulation
Analog Ground.
content
Reset Input for POK.
This input resets the 215ms timer of the POK signal.
As long as RSI is low the POK signal will work as described above.
A high input to RSI will reset the 215ms POK timer and delay the signal as long as RSI
valid
stays high. A RSI low-to-high transition restarts the 215ms counter as long as the output voltage is within regulation.
7 FB
Note:
Do not leave this pin floating.
Feedback Pin
. Feedback input to the gm error amplifier. Connect a resistor divider tap to this pin. The output can be adjusted from 0.6V to 5.25V by V
OUT
= 0.6V[1+(R1/R2)].
If the fixed output voltage version is used, connect this pin to V
OUT
.
Analog Ground.
GND and PGND should only have one point connection.
8 GND
9
10
11
PGND
Power-Ground.
Connect all power grounds to this pin.
Switch Node Connection to Inductor.
This pin connects to the drains of the internal main
Technical
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AS1335
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in
may cause permanent damage to the device. These are stress ratings only,
device reliability.
Table 2. Absolute Maximum Ratings
Parameter Min Max Units Comments
VIN to GND -0.3
6 V
SW to GND
EN, FB to GND
P-Channel Switch Source Current (DC)
N-Channel Switch Source Current (DC)
Peak SW Sink and Source Current
Thermal Resistance
Θ
JA
Latch-Up
Electrostatic Discharge
Operating Temperature Range
Storage Temperature Range
Junction Temperature
Package Body Temperature
-0.3
V
IN
+ 0.3
-0.3
-100
-40
-65
2
V
IN
1.5
1.5
3
36.7
100
+85
+150
125
V
V
A
A
A
valid
ºC/W mA kV
AG
on PCB
ºC
still
The reflow peak soldering temperature (body
+260
ams
ºC temperature) specified is in accordance with
IPC/JEDEC J-STD-020D “Moisture/Reflow
Sensitivity Classification for Non-Hermetic
Solid State Surface Mount Devices”.
The lead finish for Pb-free leaded packages is matte tin (100% Sn).
content
Technical
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AS1335
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
V
IN
= EN = 3.6V, V
OUT
= V
IN
-0.5V, T
AMB
= -40°C to +85°C, typ. values @ T
AMB
= +25ºC (unless otherwise specified).
Table 3. Electrical Characteristics
Symbol Parameter
V
IN
Input Range
V
POK t
DELAY
Power Good Low
Voltage Threshold
Conditions
Rising
Falling
Rising
Falling
Min Typ
2.6
Max Units
I
Q
Quiescent Supply
Current
1
300 400 µA
Normal Operation; V
FB
= 0.5V or V
OUT
=
90% of regulated output voltage,
I
LOAD
= 0 A
I
OUT
I
SHDN
Regulation
V
OUT
V
FB
I
FB
Δ
V
LNR
Δ
V
LOADREG
Output Current RMS
Shutdown Current
Regulated Output
DC-DC Switches
Voltage
Regulated Feedback
Voltage
2,3
Feedback Current
3
Reference Voltage
Line Regulation
Output Voltage
Load Regulation
V
IN
I
PK
Peak Current
R
PFET
P-Channel FET R
DS(ON)
R
NFET
N-Channel R
DS(ON)
I
LSW
SW
Shutdown Mode; V
EN
= 0V,
V
IN
= 4.2V
fixed V
OUT
0.975
adjustable V
OUT
0.6
T
AMB
+25°C
T
AMB
= -40°C to +85°C
V
IN
AG
I
LOAD
= 0A to 1.5A
ams
I
I
LSW
LSW
V
EN
= 0V, V
SW
= 0V or 5V,
V
IN
= 5V
OUT
= 90% of
0.5850
-30
-1
1.5
0.1
1.0
0.6
100
100
2.4
0.4
0.35
1
1.025
V
IN
-
0.5V
V
+30 nA mA
A
Ω
Ω
A
µA
V
V
valid
mV
0.01 +1 µA
Enable
1.4
V
IH
V
IL
Logic Input Threshold
I
EN
EN Leakage Current
Power-OK Output
Input High
Input Low
V
IN
= 3.6V, V
EN
= 0V to 3.6V
-1 0.01
0.4
+1
V
µA
89.5
85
92
88
94.5
91
108.2
110.7
113.2
104 107 110
150 215 275
%
V
OUT
%
V
OUT ms POK Delay Time
POK Output Voltage
Low
V
OL
I
SINK
= 1mA, V
FB
= 0.7V
0.3
V www.austriamicrosystems.com/DC-DC_Step-Down/AS1335 Revision 1.03
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AS1335
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
Table 3. Electrical Characteristics
Symbol Parameter
I
POK
POK Output Leakage
Current
Oscillator
Conditions
V
POK
= V
IN
= 3.6V
Min Typ
0.01
Max Units
1 µA f
OSC
Oscillator Frequency 1.2 1.5
1.8 MHz
V
FB
= 0.6V or V
OUT
= 100% of regulated output voltage
Thermal Shutdown
Thermal Shutdown 150 °C
Thermal Shutdown
Hysteresis cent Current is measured while the DC-DC Converter is not switching.
25
1. The dynamic supply current is higher due to the gate charge delivered at the switching frequency. The Quies-
2. The device is tested in a proprietary test mode where V
FB
is connected to the output of the DC/DC converter.
°C
valid
3. Only valid for the adjustable version;
Note:
SQC (Statistical Quality Control) methods.
AG still
Technical
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AS1335
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
7 Typical Operating Characteristics
V
OUT
= 1.0V,
I
OUT
= 100mA,
T
AMB
= +25°C (unless otherwise specified).
Figure 3. Efficiency vs. Output Current, V
OUT
= 1.0V
100
90
80
Figure 4. Efficiency vs. Output Current, V
OUT
= 1.5V
100
90
80
70 70
60 60
50
40
50
40
30 30
20
10
Vin = 5.5V
Vin = 4.0V
Vin = 3.5V
Vin = 3.0V
Vin = 2.5V
20
10
Vi n = 5.5V
Vi n = 5.0V
Vi n = 4.0V
Vi n = 3.6V
Vi n = 2.6V
0
0
10 100 1000
Output Current (mA)
10000
Figure 5. Efficiency vs. Output Current, V
OUT
= 2.5V
100
90
80
70
60
50
40
30
20
10
0
100
90
10
AG
100 1000
Output Current (mA)
OUT
10000
= 3.0V
80
70
ams
Vi n = 5.5V
Vi n = 5.0V
Vi n = 4.0V
Vi n = 3.6V
60
50
40
content
10
0
Vi n = 5.5V
Vi n = 5.0V
Vi n = 4.0V
Vi n = 3.6V
10 100 1000
Output Current (mA)
10000 10 100 1000
Output Current (mA)
10000
valid
Figure 7. Efficiency vs. Output Current, V
OUT
= 3.5V
100
90
80
70
10
0
60
50
40
30
20
10
Technical
Vi n = 5.5V
Vi n = 5.0V
Vi n = 4.5V
Vi n = 4.0V
100 1000
Output Current (mA)
10000 www.austriamicrosystems.com/DC-DC_Step-Down/AS1335
Figure 8. Efficiency vs. Input Voltage, V
OUT
= 1.0V
100
90
80
70
60
50
40
2.5
Revision 1.03
Iout = 100mA
Iout = 300mA
Iout = 700mA
Iout = 1000mA
Iout = 1500mA
3.5
4.5
Input Voltage (V)
5.5
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AS1335
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
Figure 9. Efficiency vs. Input Voltage, V
OUT
= 3.5V
100
90
80
Figure 10. Load Regulation, V
OUT
= 1.0V
1.05
1.03
1.01
70
60
50
2.6
1.45
1.4
1.35
1.3
10
3
Iout = 400mA
Iout = 600mA
Iout = 800mA
Iout = 950mA
3.4
3.8
4.2
Input Voltage (V)
4.6
5
0.99
0.97
0.95
Figure 12. Line Regulation, V
1.02
0.98
10
AG
Vin = 5.5V
Vin = 5.0V
Vin = 4.5V
Vin = 3.5V
Vin = 2.5V
100
OUT
1000
Output Current (mA)
still
10000
valid
Figure 11. Load Regulation, V
OUT
= 1.5V
1.7
1.65
1.6
1.55
1.5
Vi n = 5.5V
Vi n = 5.0V
Vi n = 3.6V
100
0.96
1000
Output Current (mA)
ams
10000
0.94
4
Input Voltage (V)
4.5
Iout = 100mA
Iout = 300mA
Iout = 700mA
Iout = 1000mA
Iout = 1500mA
5 5.5
Figure 13. Load Step 40mA to 500mA; V
IN
= 4V Figure 14. Load Step 40mA to 1A; V
IN
= 4V
Technical
100µs/Div www.austriamicrosystems.com/DC-DC_Step-Down/AS1335 Revision 1.03
100µs/Div
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AS1335
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
Figure 15. Shutdown Response; V
IN
= 3.4V Figure 16. Startup Response; V
IN
= 3.4V
200µs/Div
Figure 17. Line Transient Response;
V
IN
= 3.5V to 4.5V, I
OUT
= 500mA
AG
20µs/Div
still valid
100µs/Div
Technical
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AS1335
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS1335 is a high-efficiency buck converter that uses a constant-frequency current-mode architecture. The device contains two internal MOSFET switches and is available with a user-adjustable output voltage.
Figure 18. AS1335 - Block Diagram
–
Ramp
Compensator
OSC
ICOMP
VIN
+
OSCN
FB
Frequency
Shift
0.6V
+
Error
Amp
–
–
AS1335
Main
still
SW
valid
EN
0.6V
Reference
0.6V +
Δ
V
OVL
0.6V -
Δ
V
OVL
OVDET
+
–
+
Digital
Logic
AG
Anti-
Shoot
Through
+
IRCMP
RSI
Shutdown
Main Control Loop
Power-OK
Compare
Logic
ams
–
content
GND
POK
PK
) at which ICOMP resets the RS latch, is controlled by the error amplifier. When I
LOAD
increases, V
FB
decreases slightly relative to the internal 0.6V reference, causing the error amplifier’s output voltage to increase until the average inductor current matches the new load current.
When the top MOSFET is off, the bottom MOSFET is turned on until the inductor current starts to reverse as indicated by the current reversal comparator (IRCMP), or the next clock cycle begins. The over-voltage detection comparator
(OVDET) guards against transient overshoots >7.8% by turning the main switch off and keeping it off until the transient is removed.
Technical
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AS1335
Datasheet - D e t a i l e d D e s c r i p t i o n
Short-Circuit Protection
This frequency reduction ensures that the inductor current has more time to decay, thus preventing runaway conditions. f
OSC
will progressively increase to 1.5MHz when V
OUT
> 0V or V
FB
> 0V.
Dropout Operation
The AS1335 is working with a low input-to-output voltage difference by operating at 100% duty cycle. In this state, the
PMOS is always on. This is particularly useful in battery-powered applications with a 3.3V output.
The AS1335 allows the output to follow the input battery voltage as it drops below the regulation voltage. The quiescent current in this state rises minimally to only 400µA (max), which aids in extending battery life. This dropout (100% duty-cycle) operation achieves long battery life by taking full advantage of the entire battery range.
The input voltage requires maintaining regulation and is a function of the output voltage and the load. The difference fore a function of the on-resistance of the internal PMOS (R proportional to the load current.
DS(ON)PMOS
valid
Note:
At low V
IN
values, the R
DS(ON)
of the P-channel switch increases
(see Electrical Characteristics on page 4)
.
Therefore, power dissipation should be taken in consideration.
Shutdown
Connecting EN to GND or logic low places the AS1335 in shutdown mode and reduces the supply current to 0.1µA. In mal operation connect EN to V
IN
or logic high.
AG
Note:
Pin EN should not be left floating.
Power-OK Functionality
The AS1335’s power-ok circuitry offers a 215ms delayed power-ok signal. As long as the output voltage is outside of
The output of the power-ok signal is delayed by 215ms.
RSI Signal
content
Thermal Shutdown
ams
Due to its high-efficiency design, the AS1335 will not dissipate much heat in most applications. However, in applications where the AS1335 is running at high ambient temperature, uses a low supply voltage, and runs with high duty cycles (such as in dropout) the heat dissipated may exceed the maximum junction temperature of the device.
As soon as the junction temperature reaches approximately 150ºC the AS1335 goes in thermal shutdown. In this mode the internal PMOS & NMOS switch are turned off. The device will power up again, as soon as the temperature falls below +125°C again.
Technical
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AS1335
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
The AS1335 is perfect for mobile communications equipment, LED matrix displays, bar-graph displays, instrumentpanel meters, dot matrix displays, set-top boxes, white goods, professional audio equipment, medical equipment, industrial controllers to name a few applications.
Adjustable Output Voltage
For the fixed output voltage (V
OUT
=1.0V) connect pin FB to V
OUT
. For the adjustable output voltage version connect a voltage divider to pin FB
.
The voltage divider from V
OUT
to GND programs the output voltage from 0.6V to 5.25V via pin FB as:
V
OUT
= 0.6V(1 + (R
1
/R
2
)) (EQ 1)
valid
Figure 19. AS1335 - Step-Down Converter, Single Li-Ion to 1.0V / 1.5A fixed Output
V
IN
2.7V to 4.2V
C
IN
22µF
100k
Ω
VIN
NC
EN
AS1335-100
SW
AG
FB
2.2µH
C
OUT
100µF
POK
GND
ams
RSI
content
2.2µH
V
IN
3.35V to 5.25V
C
OUT
100µF
C
IN
22µF
VIN
SW
NC
PGND
AS1335-AD
100k
Ω
EN
GND
FB
POK
RSI
GND
Technical
680k
Ω
V
OUT
3.3V
150k
Ω www.austriamicrosystems.com/DC-DC_Step-Down/AS1335 Revision 1.03
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AS1335
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
External Component Selection
Inductor Selection
For most applications the value of the external inductor should be in the range of 2.2µH to 4.7µH as the inductor value has a direct effect on the ripple current. The selected inductor must be rated for its DC resistance and saturation current. The inductor ripple current (
Δ
I
L
) decreases with higher inductance and increases with higher V
IN
or V
OUT
.
In
the maximum inductor current in PWM mode under static load conditions is calculated. The saturation current of the inductor should be rated higher than the maximum inductor current as calculated with
sients.
Δ
I
L
=
V
OUT
×
1 –
V
-------------
V
-----------------------
L
×
f
I
LMAX
=
I
OUTMAX
+
Δ
I
--------
2 f = Switching Frequency (1.5 MHz typical)
L = Inductor Value
I
Lmax
= Maximum Inductor current
Δ
I
L =
Peak to Peak inductor ripple current
The recommended starting point for setting ripple current is
Δ
AG
I
L
= 600mA (40% of 1.5A).
still
(EQ 3)
The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. Thus, a 1.8A rated inductor should be sufficient for most applications (1.5A + 300mA).
Note: ams
Accepting larger values of ripple current allows the use of low inductance values, but results in higher output voltage ripple, greater core losses, and lower output current capability.
The total losses of the coil have a strong impact on the efficiency of the DC/DC conversion and consist of both the losses in the DC resistance and the following frequency-dependent components:
1. The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies).
2. Additional losses in the conductor from the skin effect (current displacement at high frequencies).
3. Magnetic field losses of the neighboring windings (proximity effect).
4. Radiation losses
.
Output Capacitor Selection
The advanced fast-response voltage mode control scheme of the AS1335 allows the use of tiny ceramic capacitors.
Because of their lowest output voltage ripple low ESR ceramic capacitors are recommended. X7R or X5R dielectric output capacitor are recommended.
At high load currents, the device operates in PWM mode and the RMS ripple current is calculated as:
Technical
RMSC
OUT
=
V
OUT
×
1 –
V
-------------
V
-----------------------
L
×
f
×
2
×
3
(EQ 4)
While operating in PWM mode the overall output voltage ripple is the sum of the voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charging and discharging the output capacitor: www.austriamicrosystems.com/DC-DC_Step-Down/AS1335 Revision 1.03
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AS1335
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
(EQ 5)
Δ
V
OUT
=
V
OUT
×
1 –
V
-------------
V
L
×
f
×
⎛
⎝
8
×
C
1
OUT
×
f
+
ESR
⎞
⎠
Higher value, low cost ceramic capacitors are available in very small case sizes, and their high ripple current, high voltage rating, and low ESR make them ideal for switching regulator applications. Because the AS1335 control loop is not dependant on the output capacitor ESR for stable operation, ceramic capacitors can be used to achieve very low output ripple and accommodate small circuit size.
At light loads, the converter operates in powersave mode and the output voltage ripple is in direct relation to the output capacitor and inductor value used. Larger output capacitor and inductor values minimize the voltage ripple in powersave mode and tighten DC output accuracy in powersave mode.
Input Capacitor Selection
In continuous mode, the source current of the PMOS is a square wave of the duty cycle V
OUT
/V
IN
. To prevent large
valid
voltage transients while minimizing the interference with other circuits caused by high input voltage spikes, a low ESR input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given as:
I
RMS
=
I
MAX
×
V
OUT
× (
----------------------------------------------------------
V
V
IN
IN
–
V
OUT
AG
)
still
(EQ 6)
where the maximum average output current I
MAX
equals the peak current minus half the peak-to-peak ripple current,
I
MAX
= I
LIM
-
Δ
I
L
/2
This formula has a maximum at V
IN
= 2V
OUT
where I
RMS
= I
OUT
/2. This simple worst-case condition is commonly used for design because even significant deviations only provide negligible affects.
The input capacitor can be increased without any limit for better input voltage filtering. Take care when using small exceeding the maximum ratings.
ams
IN
step on the input, can induce ringing at the VIN pin. This ringing can then couple to the output and be mistaken as loop instability, or could even damage the part by
Ceramic Input and Output Capacitors
When choosing ceramic capacitors for C
IN
and C
OUT
content
These dielectrics have the best temperature and voltage characteristics for a given value and size. Y5V and Z5U dielectric capacitors, aside from their wide variation in capacitance over temperature, become resistive at high frequencies and therefore should not be used.
Table 4. Recommended External Components
Name
C
OUT
C
IN
, C
OUT
Part Number Value Rating
T520B107M006ATE040 100µF 6.3V
Type
Tantal
Size
B
(3.5x2.8x1.9mm)
Manufacturer
Kemet www.kemet.com
X5R 0805
Murata www.murata.com
35m
Ω
6.8x6.0x2.4mm
Coilcraft www.coilcraft.com
50m
Ω
6.8x6.0x2.4mm
L
GRM21BR60J226ME39
MOS6020-222ML
MOS6020-472ML
22µF
2.2µH
4.7µH
6.3V
3.26A
1.82A
that either a higher input capacity or a capacitance with a higher rated voltage is used.
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AS1335
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
Efficiency
The efficiency of a switching regulator is equivalent to:
Efficiency = (P
OUT
/P
IN
)x100% (EQ 7)
For optimum design, an analysis of the AS1335 is needed to determine efficiency limitations and to determine design changes for improved efficiency. Efficiency can be expressed as:
Where:
ciency calculation:
Efficiency = 100% – (L
1
+ L
2
+ L
3
+ ...)
L
1
, L
2
, L
3
, etc. are the individual losses as a percentage of input power.
(EQ 8)
valid
Input Voltage Quiescent Current Losses
The V
IN
current is the DC supply current given in the electrical characteristics which excludes MOSFET driver and control currents. V
IN
current results in a small (<0.1%) loss that increases with V
IN
, even at no load. The V
IN
quiescent current loss dominates the efficiency loss at very low load currents.
I²R Losses
AG still
tances of the internal switches (R
SW)
and the external inductor (R
L
). In continuous mode, the average output current flowing through inductor L is split between the internal switches. Therefore, the series resistance looking into the SW pin is a function of both NMOS & PMOS R
DS(ON)
as well as the the duty cycle (DC) and can be calculated as follows:
The R
DS(ON) losses calculate as follows:
Switching Losses
R
SW
= (R
DS(ON)PMOS
)(DC) + (R
DS(ON)NMOS
)(1 – DC)
I²R losses = I
OUT
Electrical Characteristics on page 4
(EQ 9)
. Thus, to obtain I²R
(EQ 10)
The switching current is the sum of the control currents and the MOSFET driver. The MOSFET driver current results from switching the gate capacitance of the power MOSFETs. If a MOSFET gate is switched from low to high to low again, a packet of charge dQ moves from V
IN
to ground. The resulting dQ/dt is a current out of V
IN
that is typically much larger than the DC bias current. In continuous mode:
I
GC
= f(Q
PMOS
+ Q
NMOS
) (EQ 11)
Where:
Q
PMOS
and Q
NMOS
are the gate charges of the internal MOSFET switches.
The losses of the gate charges are proportional to V
IN
and thus their effects will be more visible at higher supply voltages.
Other Losses
Technical
IN
has adequate charge storage and very low ESR at the given switching frequency, the internal battery and fuse resistance losses can be minimized. C
IN
and C
OUT
ESR dissipative losses and inductor core losses generally account for less than 2% total additional loss.
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AS1335
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
Checking Transient Response
The main loop response can be evaluated by examining the load transient response. Switching regulators normally take several cycles to respond to a step in load current. When a load step occurs, V
OUT
immediately shifts by an amount equivalent to:
V
DROP
=
Δ
I
LOAD
x ESR (EQ 12)
Where:
ESR is the effective series resistance of C
OUT
.
Δ
I
LOAD
also begins to charge or discharge C
OUT
, which generates a feedback error signal. The regulator loop then acts to return V
OUT
to its steady-state value. During this recovery time V
OUT
can be monitored for overshoot or ringing that
!
!
!
! would indicate a stability problem.
Layout Considerations
The AS1335 requires proper layout and design techniques for optimum performance.
!
The power traces (GND, SW, and VIN) should be kept as short, direct, and wide as is practical.
the internal power MOSFETs.
Switching node SW should be kept far away from the sensitive FB node.
The negative plates of C
valid
Pin FB should be connected directly to the Output Voltage.
The positive plate of C
IN
should be connected as close to VIN as is practical since C
IN
provides the AC current to
still
recommended.
IN
and C
OUT
AG
Technical
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15 - 18
AS1335
Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s
10 Package Drawings and Markings
The device is available in an 10-pin TDFN 3x3mm package.
Figure 21. 10-pin TDFN 3x3mm Package
D
SEE
DETAIL B
B
D2
D2/2
L
PIN 1 INDEX AREA
(D/2 xE/2)
Symbol
A
A1
A3
L1
L2 aaa bbb ccc ddd eee ggg
PIN 1 INDEX AREA
(D/2 xE/2)
DETAIL B
Min
0.70
0.00
0.03
aaa C 2x
TOP VIEW e
N N-1
(ND-1) X e e
BTM VIEW
Terminal Tip ccc C
0.08 C
AG
SIDE VIEW
ODD TERMINAL SIDE
Typ
0.75
0.02
0.20 REF
Datum A or B
Max
0.80
0.05
0.15
0.13
ams
1, 2
1, 2
1, 2
1, 2
1, 2
Symbol Min
D BSC
E BSC
θ
K
0º
0.20
3.00
3.00
0.40
Typ
0.15
0.10
0.18
0.10
0.05
0.08
0.10
1, 2
1, 2
1, 2
1, 2 b e
N
ND
0.25
0.50
10
5 b ddd bbb C A B
PLANE
Max
2.70
1.75
0.50
14º
0.30
K
C
Notes
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2
1, 2, 5
1, 2
1, 2, 5
valid
Notes:
1.
Figure 21 is shown for illustration only.
2. All dimensions are in millimeters; angles in degrees.
3. Dimensioning and tolerancing conform to
ASME Y14.5 M-1994
.
Technical
JEDEC 95-1, SPP-012
. Details of terminal #1 identifier are optional, but must be located within the zone indicated. The terminal #1 identifier may be either a mold or marked feature.
6. Dimension b applies to metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip.
7. ND refers to the maximum number of terminals on side D.
8. Unilateral coplanarity zone applies to the exposed heat sink slug as well as the terminals.
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AS1335
Datasheet - O r d e r i n g I n f o r m a t i o n
11 Ordering Information
The device is available as the following standard versions.
Table 5. Ordering Information
Ordering Code Marking
AS1335-BTDT-100
AS1335-BTDT-AD
ASSI
ASSC
Description Delivery Form
1.5A, 1.5MHz, Synchronous DC/DC Step-Down
Converter, fixed V
OUT
= 1.0V
Tape and Reel
1.5A, 1.5MHz, Synchronous DC/DC Step-Down
Converter, user-adjustable Output Voltage
Tape and Reel
Package
10-pin TDFN
3x3mm
10-pin TDFN
3x3mm
Note:
All products are RoHS compliant and Pb-free.
Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect
For further information and requests, please contact us mailto:[email protected]
or find your local distributor at http://www.austriamicrosystems.com/distributor
AG still valid
Technical
www.austriamicrosystems.com/DC-DC_Step-Down/AS1335 Revision 1.03
17 - 18
AS1335
Datasheet
Copyrights
Copyright © 1997-2009, austriamicrosystems AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe.
Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner.
All products and companies mentioned are trademarks or registered trademarks of their respective companies.
Disclaimer
Devices sold by austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. austriamicrosystems AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. austriamicrosystems AG reserves the right to change specifications and prices at any time and without notice.
Therefore, prior to designing this product into a system, it is necessary to check with austriamicrosystems AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by
valid
austriamicrosystems AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location.
The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However, austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not limited to austriamicrosystems AG rendering of technical or other services.
AG still
Contact Information
Headquarters austriamicrosystems AG
Tobelbaderstrasse 30
A-8141 Unterpremstaetten, Austria
Technical
For Sales Offices, Distributors and Representatives, please visit: http://www.austriamicrosystems.com/contact www.austriamicrosystems.com/DC-DC_Step-Down/AS1335 Revision 1.03
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