LT1934/LT1934-1
Micropower Step-Down
Switching Regulators
in ThinSOT
FEATURES
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Wide Input Voltage Range: 3.2V to 34V
Micropower Operation: I
Q
= 12µA
5V at 250mA from 6.5V to 34V Input (LT1934)
5V at 60mA from 6.5V to 34V Input (LT1934-1)
3.3V at 250mA from 4.5V to 34V Input (LT1934)
3.3V at 60mA from 4.5V to 34V Input (LT1934-1)
Low Shutdown Current: <1µA
Low V
CESAT
Switch: 200mV at 300mA
Low Profile (1mm) SOT-23 (ThinSOT
TM
) Package
APPLICATIO S
s
s
s
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The LT
®
1934 is a micropower step-down DC/DC con-
verter with internal 400mA power switch, packaged in a
low profile (1mm) ThinSOT. With its wide input range of
3.2V to 34V, the LT1934 can regulate a wide variety of
power sources, from 4-cell alkaline batteries and 5V logic
rails to unregulated wall transformers and lead-acid bat-
teries. Quiescent current is just 12µA and a zero current
shutdown mode disconnects the load from the input
source, simplifying power management in battery-pow-
ered systems. Burst Mode
®
operation and the low drop
internal power switch result in high efficiency over a broad
range of load current.
The LT1934 provides up to 300mA of output current. The
LT1934-1 has a lower current limit, allowing optimum
choice of external components when the required output
current is less than 60mA. Fast current limiting protects
the LT1934 and external components against shorted
outputs, even at 34V input.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
Wall Transformer Regulation
Automotive Battery Regulation
Standby Power for Portable Products
Distributed Supply Regulation
Industrial Control Supplies
TYPICAL APPLICATIO
3.3V Step-Down Converter
D2
100
LT1934
V
IN
= 12V
BOOST
V
IN
4.5V TO 34V
V
IN
LT1934
SHDN
GND
FB
SW
0.22µF
EFFICIENCY (%)
L1
47µH
90
C2
2.2µF
D1
10pF
1M
V
OUT
3.3V
250mA
80
V
OUT
= 3.3V
70
+
ON OFF
C1
100µF
604k
60
C1: SANYO 4TPB100M
C2: TAIYO YUDEN GMK325BJ225MN
D1: ON SEMICONDUCTOR MBR0540
D2: CENTRAL CMDSH-3
L1: SUMIDA CDRH4D28-470
1934 TA01
50
0.1
U
Efficiency
V
OUT
= 5V
1
10
100
LOAD CURRENT (mA)
1934 TA02
U
U
1934f
1
LT1934/LT1934-1
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
BOOST 1
GND 2
FB 3
6 SW
5 V
IN
4 SHDN
Input Voltage (V
IN
) ................................................. 34V
BOOST Pin Voltage ................................................. 40V
BOOST Pin Above SW Pin ...................................... 20V
SHDN Pin ............................................................... 34V
FB Voltage ................................................................ 6V
SW Voltage ............................................................... V
IN
Operating Temperature Range (Note 2) ..........................
LT1934E/LT1934E-1 ......................... – 40°C to 85°C
LT1934I/LT1934I-1 ......................... – 40°C to 125°C
Maximum Junction Temperature .......................... 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
LT1934ES6
LT1934ES6-1
LT1934IS6
LT1934IS6-1
S6 PART MARKING
LTXP
LTF8
LTAJB
LTAJC
S6 PACKAGE
6-LEAD PLASTIC SOT-23
T
JMAX
= 125°C,
θ
JA
= 250°C/ W,
θ
JC
= 102°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 10V, V
BOOST
= 15V, unless otherwise noted.
PARAMETER
Undervoltage Lockout
–40°C
≤
T
A
≤
85°C
–40°C
≤
T
A
≤
125°C
q
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
3
3
3
12
12
12
0.01
MAX
3.2
3.6
3.6
22
26
26
2
1.27
1.27
±15
±60
2.3
UNITS
V
V
V
µA
µA
µA
µA
V
V
mV
nA
nA
%/V
µs
µs
%
%
Quiescent Current
V
FB
= 1.3V
–40°C
≤
T
A
≤
85°C
–40°C
≤
T
A
≤
125°C
–40°C
≤
T
A
≤
85°C
–40°C
≤
T
A
≤
125°C
–40°C
≤
T
A
≤
85°C
–40°C
≤
T
A
≤
125°C
V
SHDN
= 0V
FB Comparator Trip Voltage
FB Comparator Hysteresis
FB Pin Bias Current
FB Voltage Line Regulation
Switch Off Time
Maximum Duty Cycle
Switch V
CESAT
Switch Current Limit
BOOST Pin Current
Minimum Boost Voltage (Note 3)
Switch Leakage Current
V
FB
= 1.25V
4V < V
IN
< 34V
V
FB
> 1V
V
FB
= 0V
V
FB
= 1V
–40°C
≤
T
A
≤
85°C
–40°C
≤
T
A
≤
125°C
q
q
q
q
V
FB
Falling
q
q
1.22
1.21
1.25
1.25
10
2
2
0.007
1.4
85
83
1.8
12
88
88
200
65
I
SW
= 300mA (LT1934)
I
SW
= 75mA (LT1934-1)
LT1934
LT1934-1
I
SW
= 300mA (LT1934)
I
SW
= 75mA (LT1934-1)
I
SW
= 300mA (LT1934)
I
SW
= 75mA (LT1934-1)
350
90
300
120
490
160
12
10
2.5
2.5
2
400
120
8.5
6.0
1.8
1.7
2
U
mV
mV
mA
mA
mA
mA
V
V
µA
1934f
W
U
U
W W
W
LT1934/LT1934-1
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 10V, V
BOOST
= 15V, unless otherwise noted.
PARAMETER
SHDN Pin Current
SHDN Input Voltage High
SHDN Input Voltage Low
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
The LT1934E and LT1934E-1 are guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
CONDITIONS
V
SHDN
= 2.3V
V
SHDN
= 34V
2.3
0.25
MIN
TYP
0.5
1.5
MAX
5
UNITS
µA
µA
V
V
ELECTRICAL CHARACTERISTICS
correlation with statistical process controls. The LT1934I and LT1934I-1
specifications are guaranteed over the –40°C to 125°C temperature range.
Note 3:
This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
TYPICAL PERFOR A CE CHARACTERISTICS
LT1934 Efficiency, V
OUT
= 5V
100
LT1934
V
OUT
= 5V
L = 47µH
90
T
A
= 25°C
80
100
V
IN
= 12V
EFFICIENCY (%)
EFFICIENCY (%)
EFFICIENCY (%)
V
IN
= 24V
70
60
50
0.1
1
10
100
LOAD CURRENT (mA)
1934 G01
LT1934-1 Efficiency, V
OUT
= 3.3V
100
500
SWITCH CURRENT LIMIT (mA)
90
EFFICIENCY (%)
LT1934-1
V
OUT
= 3.3V
L = 100µH
T
A
= 25°C
V
IN
= 12V
V
IN
= 24V
80
300
OFF TIME (µs)
70
60
50
0.1
1
10
100
1934 G04
LOAD CURRENT (mA)
U W
LT1934 Efficiency, V
OUT
= 3.3V
LT1934
V
OUT
= 3.3V
L = 47µH
90
T
A
= 25°C
80
V
IN
= 24V
V
IN
= 12V
70
100
LT1934-1 Efficiency, V
OUT
= 5V
LT1934-1
V
OUT
= 5V
L = 150µH
T
A
= 25°C
V
IN
= 12V
80
V
IN
= 24V
70
90
V
IN
= 5V
60
60
50
0.1
50
1
10
100
LOAD CURRENT (mA)
1934 G02
0.1
1
10
100
1934 G03
LOAD CURRENT (mA)
Current Limit vs Temperature
3.0
LT1934
400
2.5
2.0
1.5
1.0
0.5
Off Time vs Temperature
200
LT1934-1
100
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1934 G05
1934 G06
1934f
3
LT1934/LT1934-1
TYPICAL PERFOR A CE CHARACTERISTICS
Frequency Foldback
16
14
SHDN PIN CURRENT (µA)
T
A
= 25°C
10
8
6
4
2
0
0
0.2
0.8
1.0
0.6
FEEDBACK PIN VOLTAGE (V)
0.4
1.2
1934 G07
FEEDBACK VOLTAGE (V)
SWITCH OFF TIME (µs)
12
Quiescent Current
vs Temperature
20
4.0
QUIESCENT CURRENT (µA)
15
UVLO (V)
10
5
0
–50 –25
Minimum Input Voltage
V
OUT
= 3.3V
6.0
LT1934
V
OUT
= 3.3V
5.5 T
A
= 25°C
BOOST DIODE TIED TO OUTPUT
INPUT VOLTAGE (V)
5.0
4.5
4.0
INPUT VOLTAGE (V)
V
IN
TO START
V
IN
TO RUN
3.5
3.0
0.1
4
U W
V
FB
vs Temperature
1.27
2.0
SHDN Bias Current
vs SHDN Voltage
T
A
= 25°C
1.26
1.5
1.25
1.0
1.24
0.5
1.23
1.22
–50 –25
0
50
25
0
75
TEMPERATURE (°C)
100
125
0
2
4
6
8
SHDN PIN VOLTAGE (V)
10
12
1934 G09
1934 G08
Undervoltage Lockout
vs Temperature
3.5
3.0
2.5
75
0
25
50
TEMPERATURE (°C)
100
125
2.0
–50 –25
75
0
25
50
TEMPERATURE (°C)
100
125
1934 G10
1934 G11
Minimum Input Voltage
V
OUT
= 5V
8
LT1934
V
OUT
= 5V
T
A
= 25°C
BOOST DIODE TIED TO OUTPUT
7
V
IN
TO START
6
V
IN
TO RUN
5
1
10
100
LOAD CURRENT (mA)
1934 G12
4
0.1
1
10
100
LOAD CURRENT (mA)
1934 G13
1934f
LT1934/LT1934-1
PI FU CTIO S
BOOST (Pin 1):
The BOOST pin is used to provide a drive
voltage, higher than the input voltage, to the internal
bipolar NPN power switch.
GND (Pin 2):
Tie the GND pin to a local ground plane below
the LT1934 and the circuit components. Return the feed-
back divider to this pin.
FB (Pin 3):
The LT1934 regulates its feedback pin to 1.25V.
Connect the feedback resistor divider tap to this pin. Set
the output voltage according to V
OUT
= 1.25V (1 + R1/R2)
or R1 = R2 (V
OUT
/1.25 – 1).
SHDN (Pin 4):
The SHDN pin is used to put the LT1934 in
shutdown mode. Tie to ground to shut down the LT1934.
Apply 2.3V or more for normal operation. If the shutdown
feature is not used, tie this pin to the V
IN
pin.
V
IN
(Pin 5):
The V
IN
pin supplies current to the LT1934’s
internal regulator and to the internal power switch. This
pin must be locally bypassed.
SW (Pin 6):
The SW pin is the output of the internal power
switch. Connect this pin to the inductor, catch diode and
boost capacitor.
BLOCK DIAGRA
V
IN
V
IN
C2
5
+
+
–
BOOST
ON TIME
12µs DELAY
OFF TIME
1.8µs DELAY
R Q′
S
Q
SW
L1
6
D1
C1
V
OUT
C3
D2
1
ON OFF
4
SHDN
W
U
U
U
V
REF
1.25V
+
ENABLE
–
2
GND
R2
3
FB
R1
FEEDBACK
COMPARATOR
1934 BD
1934f
5
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