LTC1751/LTC1751-3.3/LTC1751-5
Micropower, Regulated
Charge Pump
DC/DC Converters
FEATURES
s
s
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s
s
s
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s
s
s
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DESCRIPTIO
5V Output Current: 100mA (V
IN
≥
3V)
3.3V Output Current: 80mA (V
IN
≥
2.5V)
Ultralow Power: 20µA Quiescent Current
Regulated Output Voltage: 3.3V
±4%,
5V
±4%,
ADJ
No Inductors
Short-Circuit/Thermal Protection
V
IN
Range: 2V to 5.5V
800kHz Switching Frequency
Very Low Shutdown Current: <2µA
Shutdown Disconnects Load from V
IN
PowerGood/Undervoltage Output
Adjustable Soft-Start Time
Available in an 8-Pin MSOP Package
The LTC
®
1751 family are micropower charge pump DC/
DC converters that produce a regulated output voltage at
up to 100mA. The input voltage range is 2V to 5.5V.
Extremely low operating current (20µA typical with no
load) and low external parts count (one flying capacitor
and two small bypass capacitors at V
IN
and V
OUT
) make
them ideally suited for small, battery-powered applica-
tions.
The LTC1751 family operate as Burst Mode
TM
switched
capacitor voltage doublers to achieve ultralow quiescent
current. They have thermal shutdown capability and can
survive a continuous short circuit from V
OUT
to GND. The
PGOOD pin on the LTC1751-3.3 and LTC1751-5 indicates
when the output voltage has reached its final value and if
the output has an undervoltage fault condition. The FB pin
of the adjustable LTC1751 can be used to program the
desired output voltage or current. An optional soft-start
capacitor may be used at the SS pin to prevent excessive
inrush current during start-up.
The LTC1751 family is available in an 8-pin MSOP
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
APPLICATIO S
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s
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Li-Ion Battery Backup Supplies
Local 3V and 5V Conversion
Smart Card Readers
PCMCIA Local 5V Supplies
White LED Backlighting
TYPICAL APPLICATIO
Regulated 5V Output from a 2.7V to 5.5V Input
V
IN
2.7V
TO 5.5V
3
C2
10µF
7
2
R1
100k
V
OUT
5V
±4%
C1
I
10µF
OUT
≤
100mA, V
IN
≥
3V
I
OUT
≤
50mA, V
IN
≥
2.7V
OUTPUT VOLTAGE (V)
V
IN
V
OUT
OFF ON
1
SHDN
PGOOD
LTC1751-5
8
6
SS
C
+
4
GND
C
–
1751 TA01
PGOOD
5
C
FLY
1µF
C
FLY
= MURATA GRM39X5R105K6.3AJ
C1, C2 = MURATA GRM40X5R106K6.3AJ
U
Output Voltage vs Input Voltage
5.2
I
OUT
= 50mA
C
FLY
= 1µF
C
OUT
= 10µF
5.1
T
A
= 85°C
T
A
= 25°C
5.0
T
A
= –40°C
4.9
4.8
2.5
3.0
3.5
4.0
4.5
INPUT VOLTAGE (V)
5.0
5.5
1751 TA02
U
U
1
LTC1751/LTC1751-3.3/LTC1751-5
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
FB/PGOOD*
V
OUT
V
IN
GND
1
2
3
4
8
7
6
5
SS
SHDN
C
+
C
–
V
IN
to GND .................................................. – 0.3V to 6V
PGOOD, FB, V
OUT
to GND ........................... – 0.3V to 6V
SS, SHDN to GND ........................ – 0.3V to (V
IN
+ 0.3V)
V
OUT
Short-Circuit Duration ............................. Indefinite
I
OUT
(Note 2)....................................................... 125mA
Operating Temperature Range (Note 3) .. – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LTC1751EMS8
LTC1751EMS8-3.3
LTC1751EMS8-5
MS8 PART MARKING
LTKL
LTKN
LTKP
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 160°C/W
*PGOOD ON LTC1751-3.3/LTC1751-5
FB ON LTC1751
Consult factory for parts specified with wider operating temperature ranges.
The
q
denotes specifications which apply over the full specified
temperature range, otherwise specifications are at T
A
= 25°C. C
FLY
= 1µF, C
IN
= 10µF, C
OUT
= 10µF unless otherwise noted.
SYMBOL
LTC1751-3.3
V
IN
V
OUT
I
CC
V
R
η
LTC1751-5
V
IN
V
OUT
I
CC
V
R
η
LTC1751
V
IN
I
CC
V
FB
I
FB
R
OUT
Input Supply Voltage
Operating Supply Current
FB Regulation Voltage
FB Input Current
Open-Loop Charge Pump Strength
2V
≤
V
IN
≤
5.5V, I
OUT
= 0mA, SHDN = V
IN
(Note 4 )
2V
≤
V
IN
≤
5.5V, I
OUT
≤
20mA
V
FB
= 1.3V
V
IN
= 2V, V
OUT
= 3.3V (Note 5)
V
IN
= 2.7V, V
OUT
= 5V (Note 5)
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
PARAMETER
Input Supply Voltage
Output Voltage
Operating Supply Current
Output Ripple
Efficiency
Input Supply Voltage
Output Voltage
Operating Supply Current
Output Ripple
Efficiency
CONDITIONS
q
MIN
2
3.17
3.17
TYP
MAX
4.4
UNITS
V
V
V
µA
mV
P-P
%
2V
≤
V
IN
≤
4.4V, I
OUT
≤
40mA
2.5V
≤
V
IN
≤
4.4V, I
OUT
≤
80mA
2V
≤
V
IN
≤
4.4V, I
OUT
= 0mA, SHDN = V
IN
V
IN
= 2.5V, I
OUT
= 40mA
V
IN
= 2V, I
OUT
= 40mA
q
q
q
3.3
3.3
18
68
80
3.43
3.43
40
q
2.7
4.8
4.8
5
5
20
75
82
2
16
1.157
– 50
8.5
6.0
1.205
5.5
5.2
5.2
50
2.7V
≤
V
IN
≤
5.5V, I
OUT
≤
50mA
3V
≤
V
IN
≤
5.5V, I
OUT
≤
100mA
2.7V
≤
V
IN
≤
5.5V, I
OUT
= 0mA, SHDN = V
IN
V
IN
= 3V, I
OUT
= 50mA
V
IN
= 3V, I
OUT
= 50mA
q
q
q
mV
P-P
%
5.5
40
1.253
50
20
12
V
µA
V
nA
Ω
Ω
2
U
V
V
V
µA
W
U
U
W W
W
LTC1751/LTC1751-3.3/LTC1751-5
The
q
denotes specifications which apply over the full specified
temperature range, otherwise specifications are at T
A
= 25°C. C
FLY
= 1µF, C
IN
= 10µF, C
OUT
= 10µF unless otherwise noted.
SYMBOL
UVL
UVH
V
OL
I
OH
I
SHDN
V
IH
V
IL
I
IH
I
IL
t
r
f
OSC
PARAMETER
PGOOD Undervoltage Low Threshold
PGOOD Low Output Voltage
PGOOD High Output Leakage
Shutdown Supply Current
SHDN Input Threshold (High)
SHDN Input Threshold (Low)
SHDN Input Current (High)
SHDN Input Current (Low)
V
OUT
Rise Time
Switching Frequency
SHDN = V
IN
SHDN = 0V
V
IN
= 3V, I
OUT
= 0mA, 10% to 90% (Note 6)
Oscillator Free Running
CONDITIONS
Relative to Regulated V
OUT
(Note 6)
I
PGOOD
= – 500µA
V
PGOOD
= 5.5V
V
IN
≤
3.6V, V
OUT
= 0V, V
SHDN
= 0V
3.6V < V
IN
, V
OUT
= 0V, V
SHDN
= 0V
q
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
–11
–8
TYP
–7
– 4.5
MAX
–3
–2
0.4
1
UNITS
%
%
V
µA
µA
µA
V
V
µA
µA
sec
kHz
LTC1751-3.3/LTC1751-5
PGOOD Undervoltage High Threshold Relative to Regulated V
OUT
(Note 6)
LTC1751/LTC1751-3.3/LTC1751-5
q
q
q
q
q
q
0.01
1.5
2
5
0.3
–1
–1
0.6ms/nF • C
SS
800
1
1
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Based on long term current density limitations.
Note 3:
The LTC1751EMS8-X is 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
correlation with statistical process controls.
Note 4:
The no load input current will be approximately I
CC
plus twice the
standing current in the resistive output divider.
Note 5:
R
OUT
≡
(2V
IN
– V
OUT
)/I
OUT
.
Note 6:
See Figure 2.
TYPICAL PERFOR A CE CHARACTERISTICS
(LTC1751-3.3)
Output Voltage vs Load Current
3.40
T
A
= 25°C
C
FLY
= 1µF
OUTPUT VOLTAGE (V)
T
A
= 25°C
T
A
= 85°C
SUPPLY CURRENT (µA)
OUTPUT VOLTAGE (V)
3.35
3.30
V
IN
= 2V
3.25
V
IN
= 2.5V
3.20
0
25
50
75
100
LOAD CURRENT (mA)
125
150
1751 G01
U W
Output Voltage vs Input Voltage
3.40
I
OUT
= 40mA
C
FLY
= 1µF
C
OUT
= 10µF
40
No Load Supply Current
vs Input Voltage
I
OUT
= 0mA
C
FLY
= 1µF
V
SHDN
= V
IN
T
A
= 85°C
20
T
A
= 25°C
T
A
= –40°C
10
3.35
T
A
= –40°C
30
3.30
3.25
3.20
2.0
2.5
3.5
4.0
3.0
INPUT VOLTAGE (V)
4.5
1751 G02
0
2.0
2.5
3.5
4.0
3.0
INPUT VOLTAGE (V)
4.5
1751 G03
3
LTC1751/LTC1751-3.3/LTC1751-5
TYPICAL PERFOR A CE CHARACTERISTICS
(LTC1751-3.3)
Power Efficiency vs Load Current
100
T
A
= 25°C
90 C
FLY
= 1µF
= 10µF
C
80
OUT
70
60
50
40
30
20
10
0
0.001
0.01
0.1
1
10
LOAD CURRENT (mA)
100
1751 G04
EFFICIENCY (%)
V
IN
= 2.75V
V
IN
= 3.3V
V
IN
= 4.4V
OUTPUT CURRENT (mA)
Start-Up
SHDN
2V/DIV
PGOOD
5V/DIV
V
OUT
1V/DIV
C
SS
= 10nF
2ms/DIV
(LTC1751-5)
Output Voltage vs Output Current
5.2
T
A
= 25°C
C
FLY
= 1µF
SUPPLY CURRENT (µA)
OUTPUT VOLTAGE (V)
5.1
5.0
4.9
4.8
0
4
U W
1751 G06
Short-Circuit Output Current
vs Input Voltage
250
T
A
= 25°C
C
FLY
= 1µF
V
IN
= 2V
200
150
100
50
2.0
2.5
3.5
4.0
3.0
INPUT VOLTAGE (V)
4.5
1751 G05
Output Ripple
Load Transient Response
I
OUT
40mA/DIV
V
OUT
AC COUPLED
50mV/DIV
V
OUT
AC COUPLED
50mV/DIV
V
IN
= 2.5V
I
OUT
= 80mA
C
OUT
= 10µF
5µs/DIV
1751 G07
V
IN
= 2.5V
50µs/DIV
1751 G08
No Load Supply Current
vs Input Voltage
40
C
FLY
= 1µF
I
OUT
= 0
V
SHDN
= V
IN
T
A
= 85°C
20
T
A
= 25°C
T
A
= –40°C
10
30
V
IN
= 3V
V
IN
= 2.7V
100
150
50
OUTPUT CURRENT (mA)
200
1751 G09
0
2.5
3.0
3.5
4.0
4.5
INPUT VOLTAGE (V)
5.0
5.5
1751 G10
LTC1751/LTC1751-3.3/LTC1751-5
TYPICAL PERFOR A CE CHARACTERISTICS
(LTC1751-5)
Power Efficiency vs Load Current
100
T
A
= 25°C
90 C
FLY
= 1µF
C
OUT
= 10µF
80
70
60
50
40
30
20
10
0
0.001
0.01
0.1
1
10
LOAD CURRENT (mA)
100
1751 G11
EFFICIENCY (%)
V
IN
= 4.1V
V
IN
= 5.5V
OUTPUT CURRENT (mA)
Start-Up
SHDN
2V/DIV
PGOOD
5V/DIV
V
OUT
2V/DIV
V
OUT
AC COUPLED
50mV/DIV
C
SS
= 10nF
2ms/DIV
PI FU CTIO S
PGOOD (Pin 1) (LTC1751-3.3/LTC1751-5):
Output Volt-
age Status Indicator. On start-up, this open-drain pin re-
mains low until the output voltage, V
OUT
, is within 4.5%
(typ) of its final value. Once V
OUT
is valid, PGOOD becomes
high-Z. If, due to a fault condition, V
OUT
falls 7% (typ) below
its correct regulation level, PGOOD pulls low. PGOOD may
be pulled up through an external resistor to any appropri-
ate reference level.
FB (Pin 1) (LTC1751):
The voltage on this pin is compared
to the internal reference voltage (1.205V) by the error
comparator to keep the output in regulation. An external
resistor divider is required between V
OUT
and FB to pro-
gram the output voltage.
V
OUT
(Pin 2):
Regulated Output Voltage. For best perfor-
mance, V
OUT
should be bypassed with a 6.8µF (min) low
ESR capacitor as close to the pin as possible .
V
IN
(Pin 3):
Input Supply Voltage. V
IN
should be bypassed
with a 6.8µF (min) low ESR capacitor.
GND (Pin 4):
Ground. Should be tied to a ground plane for
best performance.
C
–
(Pin 5):
Flying Capacitor Negative Terminal.
C
+
(PIN 6):
Flying Capacitor Positive Terminal.
SHDN (Pin 7):
Active Low Shutdown Input. A low on
SHDN disables the device. SHDN must not be allowed to
float.
SS (Pin 8):
Soft-Start Programming Pin. A capacitor on SS
programs the start-up time of the charge pump so that
large start-up input current is eliminated.
U W
1751 G13
Short-Circuit Output Current
vs Input Voltage
250
T
A
= 25°C
C
FLY
= 1µF
V
IN
= 2.7V
200
150
100
50
2.0
2.5
3.0 3.5 4.0 4.5
INPUT VOLTAGE (V)
5.0
5.5
1751 G12
Output Ripple
Load Transient Response
I
OUT
50mA/DIV
V
OUT
AC COUPLED
50mV/DIV
V
IN
= 3V
I
OUT
= 100mA
C
OUT
= 10µF
5µs/DIV
1751 G14
V
IN
= 3V
50µs/DIV
1751 G15
U
U
U
5
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