ams AS1310-BTDT-18 Ultra low quiescent current, hysteretic dc-dc step-up converter Datasheet

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Datasheet
AS1310
U l t r a L o w Q u i e s c e n t C u r r e n t , H y s te r e t i c D C - D C S t e p - U p C o n v e r t e r
1 General Description
2 Key Features
Fixed output voltage range: 1.8V to 3.3V
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Input voltage range: 0.7V to 3.6V
The AS1310 is an ultra low IQ hysteretic step-up DC-DC converter
optimized for light loads (60mA), where it achieves efficiencies of up
to 92%.
Output current: 60mA @ VIN=0.9V, VOUT=1.8V
AS1310 operates from a 0.7V to 3.6V supply and supports output
voltages between 1.8V and 3.3V. Besides the available AS1310
standard variants any variant with output voltages in 50mV steps are
available. See Ordering Information on page 18 for more information.
Quiescent current: 1µA (typ.)
Up to 92% efficiency
If the input voltage exceeds the output voltage the device is in a
feed-through mode and the input is directly connected to the output
voltage.
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Shutdown current: < 100nA
Output disconnect in shutdown
Feedthrough mode when VIN > VOUT
Adjustable low battery detection
In order to save power the AS1310 features a shutdown mode,
where it draws less than 100nA. During shutdown mode the battery
is disconnected from the output.
TDFN (2x2) 8-pin package
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In light load operation, the device enters a sleep mode when most of
the internal operating blocks are turned off in order to save power.
This mode is active approximately 50µs after a current pulse
provided that the output is in regulation.
No external diode or transistor required
Over temperature protection
3 Applications
The AS1310 also offers adjustable low battery detection. If the
battery voltage decreases below the threshold defined by two
external resistors on pin LBI, the LBO output is pulled to logic low.
The AS1310 is an ideal solution for single and dual cell powered
devices as blood glucose meters, remote controls, hearing aids,
wireless mouse or any light-load application.
The AS1310 is available in a TDFN (2x2) 8-pin package.
Figure 1. AS1310 Typical Application Diagram
R1
LX
R2
On
Off
1
LBI
LBO
AS1310
R3
VOUT
1.8V to 3.3V
4
VOUT
C2
22µF
5
7
REF
EN
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Low Battery Detect
6
VIN
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C1
22µF
3
8
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VIN
0.7V to 3.6V
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L1
6.8µH
2
CREF
100nF
GND
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AS1310
Datasheet - P i n A s s i g n m e n t s
4 Pin Assignments
1
8
VIN
GND
2
7
EN
6
LBO
5
REF
AS1310
3
VOUT
4
Exposed pad
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LX
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LBI
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Figure 2. Pin Assignments (Top View)
4.1 Pin Descriptions
Table 1. Pin Descriptions
Pin Number
Pin Name
Description
1
LBI
Low Battery Comparator Input. 0.6V Threshold. May not be left floating. If connected to GND, LBO is
working as Power Output OK.
2
GND
Ground
3
LX
4
VOUT
5
REF
Reference Pin. Connect a 100nF ceramic capacitor to this pin.
6
LBO
Low Battery Comparator Output. Open-drain output.
7
EN
Enable Pin. Logic controlled shutdown input.
1 = Normal operation;
0 = Shutdown; shutdown current <100nA.
VIN
Battery Voltage Input. Decouple VIN with a 22µF ceramic capacitor as close as possible to VIN and
GND.
NC
Exposed Pad. This pad is not connected internally. Can be left floating or connect to GND to achieve an
optimal thermal performance.
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Output Voltage. Decouple VOUT with a ceramic capacitor as close as possible to VOUT and GND.
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8
External Inductor Connector.
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AS1310
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 Characteristics on page 4 is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
Table 2. Absolute Maximum Ratings
Min
Max
Units
Electrical Parameters
Comments
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Parameter
-0.3
+5
V
LX, REF to GND
-0.3
VOUT + 0.3
V
Input Current (latch-up immunity)
-100
100
mA
Norm: JEDEC 78
±2
kV
Norm: MIL 883 E method 3015
58
ºC/W
Electrostatic Discharge
Electrostatic Discharge HBM
Temperature Ranges and Storage Conditions
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Thermal Resistance θJA
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VIN, VOUT, EN, LBI, LBO to GND
Junction Temperature
Storage Temperature Range
-55
Package Body Temperature
Humidity non-condensing
5
ºC
+125
ºC
+260
ºC
85
%
1
The reflow peak soldering temperature (body
temperature) specified is in accordance with IPC/
JEDEC J-STD-020“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).
Represents a maximum floor life time of unlimited
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Moisture Sensitive Level
+125
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AS1310
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
All limits are guaranteed. The parameters with Min and Max values are guaranteed by production tests or SQC (Statistical Quality Control)
methods.
VIN = 1.5V, C1 = C2 = 22µF, CREF = 100nF, Typical values are at TAMB = +25ºC (unless otherwise specified). All limits are guaranteed. The
parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality Control) methods.
Symbol
Parameter
Conditions
Min
TAMB
Operating Temperature Range
-40
Input Voltage Range
0.7
Typ
Input
Minimum Startup Voltage
ILOAD = 1mA, TAMB = +25°C
0.7
Regulation
Output Voltage Range
1.8
Output Voltage Tolerance
VOUT Lockout Threshold
Operating Current
3.6
V
0.8
V
3.3
V
1
+2
%
ILOAD = 10mA
-3
+3
%
Rising Edge
1.55
1.75
V
100
nA
1.2
µA
100
nA
Quiescent Current VOUT
VOUT = 1.02xVON, REF = 0.99xVON,
No load, TAMB = +25°C
Shutdown Current
TAMB = +25ºC
NMOS
RON
0.8
VOUT = 3V
PMOS
1.65
1
0.35
Ω
0.5
Ω
3.6
4.2
4.8
µs
Peak Current Limit
320
400
480
mA
Zero Crossing Current
5
20
35
mA
Enable, Reference
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NMOS maximum On-time
IPEAK
EN Input Voltage High
VENL
EN Input Voltage Low
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VENH
0.7
V
0.1
V
EN Input Bias Current
EN = 3.6V, TAMB = +25°C
100
nA
REF Input Bias Current
REF = 0.99xVOUTNOM, TAMB = +25°C
100
nA
0.63
V
ch
IREF
°C
-2
VOUT = 1.02xVOUTNOM,
REF = 0.99xVOUTNOM, TAMB = +25°C
Switches
IEN
+85
ILOAD = 10 mA, TAMB = +25°C
Quiescent Current VIN
IQ
ISHDN
Units
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VOUT
Max
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VIN
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Table 3. Electrical Characteristics
Low Battery & Power-OK
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VLBI
LBI Threshold
Falling Edge
0.57
LBI Hysteresis
0.6
25
ILBI
LBI Leakage Current
VLBO
LBO Voltage Low
ILBO = 1mA
ILBO
LBO Leakage Current
LBO = 3.6V, TAMB = +25°C
Power-OK Threshold
LBI = 0V, Falling Edge
2
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LBI = 3.6V, TAMB = +25°C
Revision 1.8
20
90
92.5
mV
100
nA
100
mV
100
nA
95
%
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AS1310
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
Conditions
Thermal Shutdown
10°C Hysteresis
Min
Typ
Max
Units
Thermal Protection
150
°C
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1. The regulator is in startup mode until this voltage is reached. Caution: Do not apply full load current until the device output > 1.75V
2. LBO goes low in startup mode as well as during normal operation if:
- The voltage at the LBI pin is below LBI threshold.
- The voltage at the LBI pin is below 0.1V and VOUT is below 92.5% of its nominal value.
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AS1310
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
TAMB = +25°C, unless otherwise specified.
Figure 3. Efficiency vs. Output Current; VOUT = 1.8V
80
75
75
70
65
60
55
50
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80
70
65
60
55
50
Vin = 0.9V
Vin = 0.9V
Vin = 1.2V
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Vin = 1.2V
45
45
Vin = 1.5V
40
0.01
L1: XPL7030-682M
85
Efficiency (%)
Efficiency (%)
90
L1: XPL2010-682M
85
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90
Figure 4. Efficiency vs. Output Current; VOUT = 1.8V
0.1
1
10
100
Vin = 1.5V
40
0.01
1000
0.1
Output Current (mA)
Figure 5. Efficiency vs. Output Current; VOUT = 3.0V
95
Efficiency (%)
100
L1: XPL2010-682M
90
75
70
65
60
Vin = 1.2V
Vin = 1.8V
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0.1
1
10
100
75
70
65
60
Vin = 0.9V
Vin = 1.2V
Vin = 1.5V
Vin = 1.8V
45
Vin = 2.4V
40
0.01
85
80
55
50
Vin = 1.5V
45
40
0.01
1000
Vin = 2.4V
0.1
Output Current (mA)
100
1000
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180
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160
Output Current (mA) .
90
85
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80
75
70
65
Iout = 1mA
Iout =10mA
55
10
Figure 8. Maximum Output Current vs. Input Voltage
L1: XPL2010-682M
60
1
Output Current (mA)
Figure 7. Efficiency vs. Input Voltage; VOUT = 1.8V
Efficiency (%)
1000
L1: XPL7030-682M
95
Vin = 0.9V
55
50
95
100
90
85
80
100
10
Figure 6. Efficiency vs. Output Current; VOUT = 3.0V
Efficiency (%)
100
1
Output Current (mA)
140
120
100
80
60
40
Vout = 1.8V
20
Vout = 3.0V
Iout =50mA
50
0
0.7
0.9
1.1
1.3
1.5
1.7
0
1.9
Input Voltage (V)
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0.5
1
1.5
2
2.5
3
Input Voltage (V)
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AS1310
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 10. RON vs. Temperature
1
1
0.95
0.9
0.9
0.8
0.85
0.7
0.8
0.6
R ON (Ω)
0.5
0.7
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0.75
0.4
0.65
0.3
0.6
0.2
0.55
0.1
0.5
0
1
2
3
4
5
6
7
8
9
10
0
-40
NM OS
-15
10
35
60
85
Temperature (°C)
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Output Current (mA)
PM OS
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Start-up Voltage (V)
Figure 9. Start-up Voltage vs. Output Current
100mV/Div
VOUT (AC)
ILX
200mA/Div
VLX
2V/Div
Figure 11. Output Voltage Ripple; VIN = 2V, VOUT = 3V,
Rload = 100Ω
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5µs/Div
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AS1310
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
8.1 Hysteretic Boost Converter
Hysteretic boost converters are so called because comparators are the active elements used to determine on-off timing via current and voltage
measurements. There is no continuously operating fixed oscillator, providing an independent timing reference. As a result, a hysteretic or
comparator based converter has a very low quiescent current. In addition, because there is no fixed timing reference, the operating frequency is
determined by external component (inductor and capacitors) and also the loading on the output.
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Ripple at the output is an essential operating component. A power cycle is initiated when the output regulated voltage drops below the nominal
value of VOUT (0.99 x VOUT).
Inductor current is monitored by the control loop, ensuring that operation is always dis-continuous.
8.1.1
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The application circuit shown in Figure 1 will support many requirements. However, further optimization may be useful, and the following is
offered as a guide to changing the passive components to more closely match the end requirement.
Input Loop Timing
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The input loop consists of the source dc supply, the input capacitor, the main inductor, and the N-channel power switch. The on timing of the Nchannel switch is determined by a peak current measurement or a maximum on time. In the AS1310, peak current is 400mA (typ) and maximum
on time is 4.2µs (typ). Peak current measurement ensures that the on time varies as the input voltage varies. This imparts line regulation to the
converter.
The fixed on-time measurement is something of a safety feature to ensure that the power switch is never permanently on. The fixed on-time is
independent of input voltage changes. As a result, no line regulation exists.
Figure 12. Simplified Boost DCDC Architecture
L1
SW2
VIN
VOUT
Q
CIN
SW1
Q
FB
COUT
RLOAD
IPK
GND
0V
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0V
On time of the power switch (Faraday’s Law) is given by:
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LI PK
T ON = ------------------------------------------------------------------ sec [volts, amps, ohms, Henry]
V IN – ( I PK R SW1 + I PK R L1 )
(EQ 1)
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Applying Min and Max values and neglecting the resistive voltage drop across L1 and SW1;
TON _ MIN =
TON _ MAX =
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LMIN I PK _ MIN
V IN _ MAX
(EQ 2)
LMAX I PK _ MAX
V IN _ MIN
(EQ 3)
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AS1310
Datasheet - D e t a i l e d D e s c r i p t i o n
Figure 13. Simplified Voltage and Current Waveforms
V
0.99VOUT_NOM
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VOUT Ripple
VOUT
B
B
VIN
VIND_TON
C
D
A
C
D
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VIND_TOFF
T
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0
TOFF
TWAIT
IL
TON
SW1_on
SW2_off
TOFF
TWAIT
IPK
0
SW2_on
SW1_off
T
T
T
Another important relationship is the “volt-seconds” law. Expressed as following:
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V ON T ON = V OFF T OFF
(EQ 4)
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Voltages are those measured across the inductor during each time segment. Figure 13 shows this graphically with the shaded segments marked
“A & B”. Re-arranging (EQ 4):
V OUT – V IN
T ON
------------ = ---------------------------V IN
T OFF
(EQ 5)
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The time segment called TWAIT in Figure 13 is a measure of the “hold-up” time of the output capacitor. While the output voltage is above the
threshold (0.99xVOUT), the output is assumed to be in regulation and no further switching occurs.
8.1.2
Inductor Choice Example
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For the AS1310 VIN_MIN = 0.9V, VOUT_MAX = 3.3V, (EQ 5) gives Ton=2.66TOFF.
Let the maximum operating on-time = 1µs.
Note that this is shorter than the minimum limit on-time of 3.6µs. Therefore from (EQ 5), TOFF = 0.376µs. Using (EQ 3), LMAX is obtained:
LMAX = 1.875µH. The nearest preferred value is 2.2µH.
This value provides the maximum energy storage for the chosen fixed on-time limit at the minimum VIN.
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AS1310
Datasheet - D e t a i l e d D e s c r i p t i o n
Energy stored during the on time is given by:
E = 0.5L ( I PK )
2
Joules (Region A in Figure 13)
(EQ 6)
If the overall time period (TON + TOFF) is T, the power taken from the input is:
2
0.5L ( I PK )
P IN = --------------------------- Watts
T
(EQ 7)
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Assume output power is 0.8 PIN to establish an initial value of operating period T.
TWAIT is determined by the time taken for the output voltage to fall to 0.99xVOUT. The longer the wait time, the lower will be the supply current of
the converter. Longer wait times require increased output capacitance. Choose TWAIT = 10% T as a minimum starting point for maximum energy
transfer. For very low power load applications, choose TWAIT ≥ 50% T.
Output Loop Timing
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8.1.3
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The output loop consists of the main inductor, P-channel synchronous switch (or diode if fitted), output capacitor and load. When the input loop is
interrupted, the voltage on the LX pin rises (Lenz’s Law). At the same time a comparator enables the synchronous switch, and energy stored in
the inductor is transferred to the output capacitor and load. Inductor peak current supports the load and replenishes the charge lost from the
output capacitor. The magnitude of the current from the inductor is monitored, and as it approaches zero, the synchronous switch is turned off.
No switching action continues until the output voltage falls below the output reference point (0.99 x VOUT).
Output power is composed of the dc component (Region C in Figure 13):
I PK T OFF
PREGION_C = V IN -------- ------------2 T
(EQ 8)
Output power is also composed of the inductor component (Region B in Figure 13), neglecting efficiency loss:
2
0.5L ( I PK )
PREGION_B = --------------------------T
(EQ 9)
Total power delivered to the load is the sum of (EQ 8) and (EQ 9):
2
P TOTAL
I PK T OFF 0.5L ( I PK )
= V IN -------- ------------- + --------------------------2 T
T
(EQ 10)
From (EQ 3) (using nominal values) peak current is given by:
T ON V IN
I PK = ------------------L
(EQ 11)
Substituting (EQ 11) into (EQ 10) and re-arranging:
2
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V IN T ON
P TOTAL = ---------------------- ( 0.9T )
2TL
(EQ 12)
0.9T incorporates a wait time TWAIT = 10% T
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Output power in terms of regulated output voltage and load resistance is:
2
V OUT
P OUT = ----------------R LOAD
(EQ 13)
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Combining (EQ 12) and (EQ 13):
2
2
V IN T ON
V OUT
- ( 0.9T )η
---------------- = --------------------R LOAD
2TL
(EQ 14)
Symbol η reflects total energy loss between input and output and is approximately 0.8 for these calculations. Use (EQ 14) to plot duty cycle
(TON/T) changes for various output loadings and changes to VIN.
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AS1310
Datasheet - D e t a i l e d D e s c r i p t i o n
8.1.4
Input Capacitor Selection
The input capacitor supports the triangular current during the on-time of the power switch, and maintains a broadly constant input voltage during
this time. The capacitance value is obtained from choosing a ripple voltage during the on-time of the power switch. Additionally, ripple voltage is
generated by the equivalent series resistance (ESR) of the capacitor. For worst case, use maximum peak current values from the datasheet.
I PEAK T ON
C IN = ------------------------V RIPPLE
CIN = 9.6µF
Nearest preferred would be 10µF.
V PK _ RIPPLE _ ESR = I PK R ESR
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Using TON = 1µs, and IPEAK = 480mA, and VRIPPLE = 50mV, EQ 15 yields:
(EQ 15)
(EQ 16)
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Typically, the ripple due to ESR is not dominant. ESR for the recommended capacitors (Murata GMR), ESR = 5mΩ to 10mΩ. For the AS1310,
maximum peak current is 480mA. Ripple due to ESR is 2.4mV to 4.8mV.
8.1.5
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Ripple at the input propagates through the common supply connections, and if too high in value can cause problems elsewhere in the system.
The input capacitance is an important component to get right.
Output Capacitor Selection
The output capacitor supports the triangular current during the off-time of the power switch (inductor discharge period), and also the load current
during the wait time (Region D in Figure 13) and on-time (Region A in Figure 13) of the power switch.
COUT =
I LOAD (TON + TWAIT )
(1 − 0.99)VOUT _ NOM
(EQ 17)
Note: There is also a ripple component due to the equivalent series resistance (ESR) of the capacitor.
8.2 Summary
User Application Defines: VINmin, VINmax, VOUTmin, VOUTmax, ILOADmin, ILOADmax
Inductor Selection:
Select Max on-time = 0.5µs to 3µs for AS1310. Use (EQ 3) to calculate inductor value.
Use (EQ 5) to determine off-time.
Use (EQ 6) to check that power delivery matches load requirements assume 70% conversion efficiency.
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Use (EQ 13) to find overall timing period value of T at min VIN and max VOUT for maximum load conditions.
Input Capacitor Selection: Choose a ripple value and use (EQ 14) to find the value.
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Output Capacitor Selection: Determine TWAIT via (EQ 6) or (EQ 13), and use (EQ 16) to find the value.
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AS1310
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 AS1310 is available with fixed output voltages from 1.8V to 3.3V in 50mV steps.
6.8µH
LX
CIN
22µF
1.8V to 3.3V
Output
Zero
Crossing
Detector
Startup
Circuitry
Driver
and
Control
Logic
VIN
VOUT
COUT
22µF
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0.7 to 3.6V
Input
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Figure 14. AS1310 Block Diagram
R3
–
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+
LBI
LBO
Imax
Detection
EN
AS1310
VREF
REF
CREF
100nF
GND
9.1 AS1310 Features
Shutdown. The part is in shutdown mode while the voltage at pin EN is below 0.1V and is active when the voltage is higher than 0.7V.
Note: EN can be driven above VIN or VOUT, as long as it is limited to less than 3.6V.
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Output Disconnect and Inrush Limiting. During shutdown VOUT is going to 0V and no current from the input source is running through
the device. This is true as long as the input voltage is higher than the output voltage.
Feedthrough Mode. If the input voltage is higher than the output voltage the supply voltage is connected to the load through the device. To
guarantee a proper function of the AS1310 it is not allowed that the supply exceeds the maximum allowed input voltage (3.6V).
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In this feedthrough mode the quiescent current is 35µA (typ.). The device goes back into step-up mode when the oputput voltage is 4% (typ.)
below VOUTNOM.
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Revision 1.8
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AS1310
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9.1.1
Power-OK and Low-Battery-Detect Functionality
LBO goes low in startup mode as well as during normal operation if:
- The voltage at the LBI pin is below LBI threshold (0.6V). This can be used to monitor the battery voltage.
- LBI pin is connected to GND and VOUT is below 92.5% of its nominal value. LBO works as a power-OK signal in this case.
The LBI pin can be connected to a resistive-divider to monitor a particular definable voltage and compare it with a 0.6V internal reference. If LBI
is connected to GND an internal resistive-divider is activated and connected to the output. Therefore, the Power-OK functionality can be realized
with no additional external components.
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The Power-OK feature is not active during shutdown and provides a power-on-reset function that can operate down to VIN = 0.7V. A capacitor to
GND may be added to generate a power-on-reset delay. To obtain a logic-level output, connect a pull-up resistor R3 from pin LBO to pin VOUT.
Larger values for this resistor will help to minimize current consumption; a 100kΩ resistor is perfect for most applications (see Figure 16 on page
13).
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For the circuit shown in the left of Figure 15, the input bias current into LBI is very low, permitting large-value resistor-divider networks while
maintaining accuracy. Place the resistor-divider network as close to the device as possible. Use a defined resistor for R2 and then calculate R1
as:
V IN
R 1 = R 2 ⋅  ----------- – 1
 V LBI

VLBI is 0.6V ±30mV
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Where:
(EQ 18)
Figure 15. Typical Application with Adjustable Battery Monitoring
L1
6.8µH
3
VIN
0.7V to 3.6V
LX
8
C1
22µF
VIN
R1
1
LBI
R2
On
Off
Low Battery Detect
6
LBO
R3
VOUT
1.8V to 3.3V
4
AS1310
VOUT
C2
22µF
5
7
REF
EN
GND
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2
CREF
100nF
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Figure 16. Typical Application with LBO working as Power-OK
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VIN
0.7V to 3.6V
LX
3
8
1
LBI
On
Off
LBO
AS1310
R3
VOUT
1.8V to 3.3V
4
VOUT
C2
22µF
5
7
REF
EN
2
www.austriamicrosystems.com/DC-DC_Step-Up/AS1310
Low Battery Detect
6
VIN
C1
22µF
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L1
6.8µH
CREF
100nF
GND
Revision 1.8
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AS1310
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9.1.2
Thermal Shutdown
To prevent the AS1310 from short-term misuse and overload conditions the chip includes a thermal overload protection. To block the normal
operation mode all switches will be turned off. The device is in thermal shutdown when the junction temperature exceeds 150°C. To resume the
normal operation the temperature has to drop below 140°C.
Note: Continuing operation in thermal overload conditions may damage the device and is considered bad practice.
9.2 Always On Operation
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A good thermal path has to be provided to dissipate the heat generated within the package. Otherwise it’s not possible to operate the AS1310 at
its usable maximal power. To dissipate as much heat as possible from the package into a copper plane with as much area as possible, it’s
recommended to use multiple vias in the printed circuit board. It’s also recommended to solder the Exposed Pad (pin 9) to the GND plane.
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In battery powered applications with long standby times as blood glucose meters, remote controls, soap dispensers, etc., a careful battery
management is required. Normally a complex power management control makes sure that the DCDC is only switched on, when it is really
needed. With AS1310 this complex control can be saved completely, since the AS1310 is perfectly suited to support always-on operations of the
application. The efficiency at standby currents of e.g. 2µAs is around 45% (see Figure 17).
100
90
L1: XPL2010-682M
80
Efficiency (%)
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Figure 17. Efficiency vs. Output Current for Always ON Operation
70
60
50
40
30
20
Vin = 1.1V
10
0
0.001
Vin = 1.5V
0.01
0.1
1
10
100
Output Current (mA)
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9.3 Component Selection
Only four components are required to complete the design of the step-up converter. The low peak currents of the AS1310 allow the use of low
value, low profile inductors and tiny external ceramic capacitors.
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9.4 Inductor Selection
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For best efficiency, choose an inductor with high frequency core material, such as ferrite, to reduce core losses. The inductor should have low
DCR (DC resistance) to reduce the I²R losses, and must be able to handle the peak inductor current without saturating. A 6.8µH inductor with a
>500mA current rating and <500mΩ DCR is recommended.
Table 4. Recommended Inductors
L
DCR
Current Rating
Dimensions (L/W/T)
XPL2010-682M
6.8µH
421mΩ
0.62A
2.0x1.9x1.0 mm
EPL2014-682M
6.8µH
287mΩ
0.59A
2.0x2.0x1.4 mm
LPS3015-682M
6.8µH
300mΩ
0.86A
3.0x3.0x1.5 mm
LPS3314-682M
6.8µH
240mΩ
0.9A
3.3x3.3x1.3 mm
LPS4018-682M
6.8µH
150mΩ
1.3A
3.9x3.9x1.7 mm
XPL7030-682M
6.8µH
59mΩ
9.4A
7.0x7.0x3.0 mm
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Part Number
www.austriamicrosystems.com/DC-DC_Step-Up/AS1310
Revision 1.8
Manufacturer
Coilcraft
www.coilcraft.com
14 - 19
AS1310
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
Table 4. Recommended Inductors
Part Number
L
DCR
Current Rating
Dimensions (L/W/T)
LQH32CN6R8M53L
6.8µH
250mΩ
0.54A
3.2x2.5x1.55 mm
LQH3NPN6R8NJ0L
6.8µH
210mΩ
0.7A
3.0x3.0x1.1 mm
LQH44PN6R8MJ0L
6.8µH
143mΩ
0.72A
4.0x4.0x1.1 mm
Manufacturer
Murata
www.murata.com
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9.5 Capacitor Selection
Table 5. Recommended Input and Output Capacitors
C
TC Code
Rated Voltage
Dimensions (L/W/T)
22µF
X5R
6.3V
0805, T=1.25mm
GRM31CR61C226KE15
22µF
X5R
16V
1206, T=1.6mm
47µF
X5R
6.3V
1206, T=1.6mm
GRM31CR60J475KA01
Manufacturer
Murata
www.murata.com
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Part Number
GRM21BR60J226ME99
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The convertor requires three capacitors. Ceramic X5R or X7R types will minimize ESL and ESR while maintaining capacitance at rated voltage
over temperature. The VIN capacitor should be 22µF. The VOUT capacitor should be between 22µF and 47µF. A larger output capacitor should
be used if lower peak to peak output voltage ripple is desired. A larger output capacitor will also improve load regulation on VOUT. See Table 5
for a list of capacitors for input and output capacitor selection.
On the pin REF a 10nF capacitor with an Insulation resistance >1GΩ is recommended.
Table 6. Recommended Capacitors for REF
Part Number
GRM188R71C104KA01
GRM31CR61C226KE15
C
TC Code
Insulation
Resistance
Rated
Voltage
Dimensions (L/W/T)
Manufacturer
100nF
X7R
>5GΩ
16V
0603, T=0.8mm
100nF
X7R
>5GΩ
50V
0805, T=1.25mm
Murata
www.murata.com
9.6 Layout Considerations
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Relatively high peak currents of 480mA (max) circulate during normal operation of the AS1310. Long printed circuit tracks can generate
additional ripple and noise that mask correct operation and prove difficult to “de-bug” during production testing. Referring to Figure 1, the input
loop formed by C1, VIN and GND pins should be minimized. Similarly, the output loop formed by C2, VOUT and GND should also be minimized.
Ideally both loops should connect to GND in a “star” fashion. Finally, it is important to return CREF to the GND pin directly.
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Revision 1.8
15 - 19
AS1310
Datasheet
10 Package Drawings and Markings
The device is available in a TDFN (2x2) 8-pin package.
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Figure 18. Drawings and Dimensions
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XXX
A2
Min
0.51
0.00
0.225
0.18
1.45
0.75
-
Nom
0.55
0.02
0.15 REF
0.325
0.25
2.00 BSC
2.00 BSC
0.50 BSC
1.60
0.90
0.15
0.10
0.10
0.05
0.08
0.10
8
Max
0.60
0.05
0.425
0.30
1.70
1.00
-
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Symbol
A
A1
A3
L
b
D
E
e
D2
E2
aaa
bbb
ccc
ddd
eee
fff
N
Notes:
1.
2.
3.
4.
5.
Dimensioning & tolerancing conform to ASME Y14.5M-1994.
All dimensions are in millimeters. Angles are in degrees.
Coplanarity applies to the exposed heat slug as well as the terminal.
Radius on terminal is optional.
N is the total number of terminals.
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Revision 1.8
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AS1310
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
Revision History
Revision
Date
Owner
Description
Initial revision
1.6
06 Mar, 2012
1.7
27 Apr, 2012
1.8
17 Aug, 2012
afe
Updated Detailed Description and Application Information sections
Detailed Description section updated
Updated thermal resistance value and (EQ 17)
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Note: Typos may not be explicitly mentioned under revision history.
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1.0
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Revision 1.8
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AS1310
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 standard products shown in Table 7.
Table 7. Ordering Information
Marking
Output
Delivery Form
Package
A2
1.8V
Tape and Reel
TDFN (2x2) 8-pin
AS1310-BTDT-20
A8
2.0V
Tape and Reel
TDFN (2x2) 8-pin
AS1310-BTDT-25
A9
2.5V
Tape and Reel
TDFN (2x2) 8-pin
AS1310-BTDT-27
A7
2.7V
Tape and Reel
TDFN (2x2) 8-pin
AS1310-BTDT-30
A6
3.0V
Tape and Reel
TDFN (2x2) 8-pin
1
tbd
3.3V
Tape and Reel
TDFN (2x2) 8-pin
2
tbd
tbd
Tape and Reel
TDFN (2x2) 8-pin
AS1310-BTDT-xx
Ultra Low Quiescent Current,
Hysteretic DC-DC Step-Up Converter
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1. On request
2. Non-standard devices are available between 1.8V and 3.3V in 50mV steps.
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AS1310-BTDT-33
Description
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Ordering Code
AS1310-BTDT-18
Note: All products are RoHS compliant and austriamicrosystems green.
Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect
Technical Support is available at http://www.austriamicrosystems.com/Technical-Support
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For further information and requests, please contact us mailto:[email protected]
or find your local distributor at http://www.austriamicrosystems.com/distributor
www.austriamicrosystems.com/DC-DC_Step-Up/AS1310
Revision 1.8
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AS1310
Datasheet - O r d e r i n g I n f o r m a t i o n
Copyrights
Copyright © 1997-2012, 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.
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Disclaimer
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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 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.
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Contact Information
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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 personal injury, property damage, loss of profits, loss of use,
interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing,
performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of
austriamicrosystems AG rendering of technical or other services.
Headquarters
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austriamicrosystems AG
Tobelbaderstrasse 30
A-8141 Unterpremstaetten, Austria
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Tel: +43 (0) 3136 500 0
Fax: +43 (0) 3136 525 01
For Sales Offices, Distributors and Representatives, please visit:
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http://www.austriamicrosystems.com/contact
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Revision 1.8
19 - 19