National Semiconductor LM2787 Technical data
LM2787
Low Noise Regulated Switched Capacitor Voltage
Inverter in micro SMD
LM2787 Low Noise Regulated Switched Capacitor Voltage Inverter in micro SMD
April 2003
General Description
The LM2787 CMOS Negative Regulated Switched Capacitor
Voltage Inverter delivers a very low noise adjustable output
for an input voltage in the range of +2.7V to +5.5V. Four low
cost capacitors are used in this circuit to provide up to 10mA
of output current. The regulated output for the LM2787 is
adjustable between −1.5V and −5.2V. The LM2787 operates
at 260 kHz (typical) switching frequency to reduce output
resistance and voltage ripple. With an operating current of
only 400 µA (charge pump power efficiency greater than
90% with most loads) and 0.05 µA typical shutdown current,
the LM2787 provides ideal performance for cellular phone
power amplifier bias and other low current, low noise negative voltage needs. The device comes in small 8-Bump micro
SMD and thin micro SMD packages.
Features
n Inverts and regulates the input supply voltage
n Small 8-Bump micro SMD and thin micro SMD
packages
n 91% typical charge pump power efficiency at 10mA
n Low output ripple
n Shutdown lowers Quiescent current to 0.05 µA (typical)
Applications
n Wireless Communication Systems
n Cellular Phone Power Amplifier Biasing
n Interface Power Supplies
n Handheld Instrumentation
n Laptop Computers and PDA’s
Typical Application Circuit and Connection Diagram
10131325
8-Bump micro SMD (Top View)
10131302
© 2003 National Semiconductor Corporation DS101313 www.national.com
Ordering Information micro SMD
LM2787
Device Order Number Package Number Package Marking
LM2787BP BPA08CCB S8 Tape and Reel (250 units/reel)
LM2787BPX BPA08CCB S8 Tape and Reel (3000 units/reel)
Thin micro SMD
Device Order Number Package Number Package Marking
LM2787TP TPA08CCA S8 Tape and Reel (250 units/reel)
LM2787TPX TPA08CCA S8 Tape and Reel (3000 units/reel)
Note:*The small physical size of the micro SMD package does not allow for
the full part number marking. Devices will be marked with the designation shown in the column Package Marking.
Pin Descriptions
Pin No. Name Function
A1 Cap+ Positive terminal for C
B1 V
C1 V
C2 V
IN
OUT
FB
Positive power supply input.
Regulated negative output voltage.
Feedback input. Connect VFBto an external resistor divider between V
adjust voltage V
C3 SD
B3 V
NEG
Active low, logic-level shutdown input.
Negative unregulated output voltage.
A3 Cap− Negative terminal for C
A2 GND Ground.
ADJ
1
(0≤V
.
ADJ≤VIN
.
1
). DO NOT leave unconnected.
*
*
Supplies As
Supplies As
and a positive
OUT
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LM2787
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V
to OUT) + 5.8V
SD
V
and V
NEG
OUT
Current 10mA
Short-Circuit Duration to GND
V
OUT
to GND or GND
IN
Continuous Output
(GND − 0.3V) to
+ 0.3V)
(V
IN
T
(Note 3) 150˚C
JMAX
θ
(Note 3) 220˚C/W
JA
Operating Input Voltage Range 2.7V to 5.5V
Operating Output Current Range 0mA to 10mA
Operating Ambient −40˚C to 85˚C
Temp. Range
Operating Junction Temp. Range −40˚C to 110˚C
Storage Temperature −65˚C to 150˚C
Lead Temp. (Soldering, 10 sec.) 300˚C
ESD Rating (Note 4) 2kV
(Note 2) 1 sec.
Continuous Power Dissipation (TA=
25˚C) (Note 3) 600mW
Electrical Characteristics
Limits with standard typeface apply for TJ= 25˚C, and limits in boldface type apply over the full temperature range. Unless
otherwise specified V
Symbol Parameter Conditions Min Typ Max Units
I
I
SD
F
SW
Supply Current Open Circuit, No Load 400 950 µA
Q
Shutdown Supply Current 0.05 1 µA
Switching Frequency
(Note 5)
η
POWER
T
R
START
NEG
V
Power Efficiency at V
Start Up time 120 600 µs
Output Resistance to V
Output Voltage Ripple
R
(Note 7)
V
Feedback Pin Reference
FB
Voltage
V
OUT
Adjustable Output Voltage 5.5V ≥ VIN≥ 2.7V, 2.5mA ≥ I
Load Regulation 0 to 10mA, V
Line Regulation 5.5V ≥ V
V
Shutdown Pin Input Voltage
IH
High
V
Shutdown Pin Input Voltage
IL
Low
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device
beyond its rated operating conditions.
Note 2: OUT may be shorted to GND for one second without damage. However, shorting OUT to V
temperatures above T
Note 3: The maximum power dissipation must be de-rated at elevated temperatures and is limited by T
temperature) and θ
Note 4: Rating is for the human body model, a 100pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 5: The output switches operate at one half the oscillator frequency, f
Note 6: Current drawn from V
Note 7: In the test circuit, capacitors C
output voltage ripple, and reduce efficiency.
Note 8: The feedback resistors R1 and R2 are 200kΩ resistors.
JA
= 3.6V, C1=C2=C3= 1µF.
IN
VIN= 3.6V 140 260 450
NEG
IL= 3.6mA
= 10mA
I
L
(Note 6) 30 Ω
NEG
IL=2.5mA, V
= 10mA, V
I
L
OUT
OUT
= −2.7V
= −3.8V
IL= 2.5mA (Note 8) −1.25 −1.20 −1.15 V
L
5.5V ≥ VIN≥ 3.0V, 10mA ≥ IL≥
−(V
IN
IN
−1.2V)
−0.3V)
−(V
0mA
= − 2.4V 5 mV/mA
OUT
≥ 2.7V, IL= 2.5mA 1 mV/V
IN
5.5V ≥ VIN≥ 2.7V 2.4 V
5.5V ≥ VIN≥ 2.7V 0.8 V
may damage the device and must be avoided. Also, for
= 85˚C, OUT must not be shorted to GND or VINor device may be damaged.
A
(junction-to-ambient thermal resistance). The maximum power dissipation at any temperature is:
PDiss
=(T
MAX
pin decreases power efficiency and will increase output voltage ripple.
NEG
1,C2
—TA)/θJAup to the value listed in the Absolute Maximum Ratings.
JMAX
=2fSW.
OSC
, and C3are 1µF, 0.30Ω maximum ESR capacitors. Capacitors with higher ESR will increase output resistance, increase
IN
(maximum junction temperature), TA(ambient
JMAX
kHz
94
91
%
1mV
V
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