Datasheet
AS1335
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 volt-
age 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 battery-
powered application.
Typical supply current with no load is 400µA and
decreases to
≤1µA
in shutdown mode. The highly effi-
cient 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 pack-
age.
2 Key Features
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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
Shutdown Mode Supply Current:
≤1µA
Current Mode Operation for Excellent Line/Load
Transient Response
Thermal Protection
10-pin TDFN 3x3mm Package
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3 Applications
The device is ideal for mobile communication devices,
laptops and PDAs, ultra-low-power systems, threshold
detectors/discriminators, telemetry and remote systems,
medical instruments, or any other space-limited applica-
tion with low power-consumption requirements.
Figure 1. AS1335 - Typical Application Diagram
V
IN
2.6V to 5.25V
C
IN
22µF
VIN
NC
SW
2.2µH
C
OUT
22µF
V
OUT
1.0V, 1.5A
PGND
AS1335
EN
POK
GND
GND
FB
RSI
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AS1335
Datasheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
VIN 1
NC 2
EN 3
POK 4
GND 5
11
10 SW
9 PGND
AS1335
8 GND
7 FB
6 RSI
Pin Descriptions
Table 1. Pin Descriptions
Pin
Number
1
2
Pin Name
VIN
NC
Description
Positive Supply Voltage.
This pin must be closely decoupled to PGND with a
≥
22µF
ceramic capacitor.
Not Connected.
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.
Power-OK Output.
Open-drain output with 215ms delay. Connect a 100kΩ pull-up resistor
to V
OUT
or pin VIN for logic levels. Leave this pin unconnected if the Power-OK feature is
not used.
LOW Signal: Out of regulation
HIGH signal: Within Regulation (after 215ms delay)
Analog Ground.
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
stays high. A RSI low-to-high transition restarts the 215ms counter as long as the output
voltage is within regulation.
Note:
Do not leave this pin floating.
7
8
9
10
11
FB
GND
PGND
SW
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.
Power-Ground.
Connect all power grounds to this pin.
Switch Node Connection to Inductor.
This pin connects to the drains of the internal main
and synchronous power MOSFET switches.
Exposed Pad.
The exposed pad must be connected to PGND. Ensure a good connection
to the PCB to achieve optimal thermal performance.
3
EN
4
POK
5
GND
6
RSI
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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
Table 2
may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in
Electrical Character-
istics on page 4
is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Table 2. Absolute Maximum Ratings
Parameter
VIN to GND
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
-40
-65
-100
2
+85
+150
125
Min
-0.3
-0.3
-0.3
Max
6
V
IN
+ 0.3
V
IN
1.5
1.5
3
36.7
100
Units
V
V
V
A
A
A
ºC/W
mA
kV
ºC
ºC
ºC
The reflow peak soldering temperature (body
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).
on PCB
@85°C, JEDEC 78
HBM MIL-Std. 883E 3015.7
methods
Comments
Package Body Temperature
+260
ºC
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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
V
IN
I
Q
I
OUT
I
SHDN
Regulation
V
OUT
Regulated Output
Voltage
Regulated Feedback
2,3
Voltage
Feedback Current
Line Regulation
Output Voltage
Load Regulation
3
Parameter
Input Voltage Range
Quiescent Supply
1
Current
Output Current RMS
Shutdown Current
Conditions
Min
2.6
Typ
Max
5.25
Units
V
µA
A
Normal Operation; V
FB
= 0.5V or V
OUT
=
90% of regulated output voltage,
I
LOAD
= 0 A
300
1.5
400
Shutdown Mode; V
EN
= 0V,
V
IN
= 4.2V
0.1
1
µA
fixed V
OUT
adjustable V
OUT
T
AMB
= +25°C
T
AMB
= -40°C to +85°C
0.975
0.6
0.5880
0.5850
-30
1.0
1.025
V
IN
-
0.5V
V
V
V
nA
mV
mA
V
FB
I
FB
ΔV
LNR
ΔV
LOADREG
0.6
0.6
0.6120
0.6150
+30
Reference Voltage
V
IN
= 2.6V to 5.25V
I
LOAD
= 0A to 1.5A
100
100
DC-DC Switches
I
PK
R
PFET
R
NFET
I
LSW
Enable
V
IH
V
IL
I
EN
Logic Input Threshold
EN Leakage Current
Input High
Input Low
V
IN
= 3.6V, V
EN
= 0V to 3.6V
-1
0.01
1.4
0.4
+1
V
µA
Peak Inductor Current
P-Channel FET R
DS(ON)
N-Channel FET R
DS(ON)
SW Leakage
V
IN
= 3V, V
FB
= 0.5V or V
OUT
= 90% of
regulated output voltage,
Duty Cycle < 35%
I
LSW
= 100mA
I
LSW
= -100mA
V
EN
= 0V, V
SW
= 0V or 5V,
V
IN
= 5V
-1
2.4
0.4
0.35
0.01
+1
A
Ω
Ω
µA
Power-OK Output
Power Good Low
Voltage Threshold
V
POK
Power Good High
Voltage Threshold
t
DELAY
V
OL
POK Delay Time
POK Output Voltage
Low
I
SINK
= 1mA, V
FB
= 0.7V
Rising
Falling
Rising
Falling
89.5
85
108.2
104
150
92
88
110.7
107
215
94.5
91
113.2
110
275
0.3
%
V
OUT
%
V
OUT
ms
V
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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
I
POK
Oscillator
f
OSC
Oscillator Frequency
V
FB
= 0.6V or V
OUT
= 100% of regulated
output voltage
1.2
1.5
1.8
MHz
Parameter
POK Output Leakage
Current
Conditions
V
POK
= V
IN
= 3.6V
Min
Typ
0.01
Max
1
Units
µA
Thermal Shutdown
Thermal Shutdown
Thermal Shutdown
Hysteresis
150
25
°C
°C
1. The dynamic supply current is higher due to the gate charge delivered at the switching frequency. The Quies-
cent Current is measured while the DC-DC Converter is not switching.
2. The device is tested in a proprietary test mode where V
FB
is connected to the output of the DC/DC converter.
3. Only valid for the adjustable version;
Note:
All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or
SQC (Statistical Quality Control) methods.
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