Power-OK Indicator: Output voltage sense. Open-drain NFET output. With an
external pull-up resistor tied to POK, V(POK) will be high when V
OUT
is
regulating correctly. When V
OUT
falls out of regulation, the internal open-drain
FET pulls the POK voltage low.
Battery-OK Indicator: Input voltage sense. Open-drain NFET output. With an
external pull-up resistor tied to BATOK, V(BATOK) will be high when V
IN
>
2.85V (typ). LM2797/98 pulls V(BATOK) low when V
IN
<
2.65V (typ.) , and/or
when the part is in shutdown [V(EN) = 0].
Enable Logic Input. High voltage = ON, Low voltage = SHUTDOWN
Second Flying Capacitor: Positive Terminal
Ground Connection
Second Flying Capacitor: Negative Terminal
Description
6
BATOK
7
8
9
10
EN
C2+
GND
C2-
Ordering Information
Nominal
Turn-on
Output
Time
Voltage
V
OUT(NOM)
1.80V
1.50V
1.80V
2.00V
100µs
400µs
400µs
400µs
Order Number
Package Marking
Supplied As:
LM2797MM-1.8
LM2797MMX-1.8
LM2798MM-1.5
LM2798MMX-1.5
LM2798MM-1.8
LM2798MMX-1.8
LM2798MM-2.0
LM2798MMX-2.0
S80B
S56B
S57B
S58B
1000 units on Tape-and Reel
3500 units on Tape-and-Reel
1000 units on Tape-and Reel
3500 units on Tape-and-Reel
1000 units on Tape-and Reel
3500 units on Tape-and-Reel
1000 units on Tape-and Reel
3500 units on Tape-and-Reel
www.national.com
2
LM2797/LM2798
Absolute Maximum Ratings
2)
(Notes 1,
Operating Ratings
Input Voltage Range
Recommended Output Current
Range
Junction Temperature Range
Ambient Temperature Range
(Note 6)
(Notes 1, 2)
2.6V to 5.5V
0mA to 120mA
-40˚C to 125˚C
-40˚C to 85˚C
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
IN
, EN, POK, BATOK pins: Voltage
to Ground (Note 3)
Junction Temperature (T
J-MAX-ABS
)
Continuous Power Dissipation
(Note 4)
V
OUT
Short-Circuit to GND Duration
(Note 4)
Storage Temperature Range
Lead Temperature
(Soldering, 5 Sec.)
ESD Rating (Note 5)
Human-body model:
Machine model
−0.3V to 5.6V
150˚C
Internally Limited
Unlimited
−65˚C to 150˚C
260˚C
2 kV
200V
(Notes 2, 8)
Thermal Information
Thermal Resistance, MSOP-8
Resistance, MSOP-8 Package
(θ
JA
) (Note 7)
220˚C/W
Electrical Characteristics
Symbol
Parameter
Limits in standard typeface and typical values apply for T
J
= 25
o
C. Limits in
boldface
type apply over the operating junction
temperature range. Unless otherwise specified: 2.6
≤
V
IN
≤
5.5V, V(EN) = V
IN
, C
1
= C
2
= 1µF, C
IN
= C
OUT
= 10µF. (Note 9)
Conditions
2.8V
≤
V
IN
≤
4.2V
0mA
≤
I
OUT
≤
120mA
4.2V
<
V
IN
≤
5.5V
0mA
≤
I
OUT
≤
120mA
2.8V
≤
V
IN
≤
4.2V
0mA
≤
I
OUT
≤
120mA
4.2V
<
V
IN
≤
5.5V
0mA
≤
I
OUT
≤
120mA
I
OUT
= 0mA
V(EN) = 0V
LM2798-1.8: V
IN
= 3.6V, I
OUT
= 120mA
LM2798-1.8: V
IN
= 3.0V, I
OUT
= 60mA
LM2798-1.5: 3.0
≤
V
IN
≤
4.2V, I
OUT
= 60mA
LM2798-1.8: 3.0
≤
V
IN
≤
4.2V, I
OUT
= 60mA
LM2798-2.0: 3.0
≤
V
IN
≤
4.2V, I
OUT
= 60mA
LM2798, V
IN
=2.6V, I
OUT
=100mA, (Note 12)
LM2797, V
IN
=2.6V, I
OUT
=100mA, (Note 12)
f
SW
I
SC
V
IH
V
IL
I
EN
Switching Frequency
Short-Circuit Current
EN pin Logic-High Input
EN pin Logic-Low Input
EN pin input current
V
EN
= 0V
V
EN
= 5.5V
V
IN
= 3.6, V
OUT
= 0V
0.9
0
0
30
Min
-5
-6
Typ
Max
+5
+6
Units
LM2797-1.8, LM2798-1.8, LM2798-2.0
% of
V
OUT(nom)
(Note 10)
V
OUT
Output Voltage Tolerance
LM2798-1.5
-6
-6
+6
+6
% of
V
OUT(nom)
(Note 10)
V
OUT
Output Voltage Tolerance
All Output Voltage Options
I
Q
I
SD
Operating Supply Current
Shutdown Supply Current
Output Voltage Ripple
Peak Efficiency
Average Efficiency over
Li-Ion Input Voltage Range
(Note 11)
Turn-On Time
35
0.1
20
90
76
82
75
400
100
500
25
50
2
µA
µA
mV
p-p
%
%
V
R
E
PEAK
E
AVG
t
ON
µs
kHz
mA
V
IN
0.4
V
V
nA
Enable Pin (EN) Characteristics
3
www.national.com
LM2797/LM2798
Electrical Characteristics
Symbol
V
T-POK
Parameter
Threshold of output voltage
for POK transition
POK-high leakage current
POL-low pull-down voltage
Input voltage threshold for
BATOK transition
BATOK-high leakage
current
BATOK-low pull-down
voltage
(Notes 2, 8) (Continued)
Limits in standard typeface and typical values apply for T
J
= 25
o
C. Limits in
boldface
type apply over the operating junction
temperature range. Unless otherwise specified: 2.6
≤
V
IN
≤
5.5V, V(EN) = V
IN
, C
1
= C
2
= 1µF, C
IN
= C
OUT
= 10µF. (Note 9)
Conditions
POK transition L to H
POK transition H to L
Hysterisis
I
POK-H
V
POK-L
V
T-BATOK
V(POK) = 3.6V
I(POK) = -100µA
BATOK transition L to H
BATOK transition H to L
Hysterisis
I
BATOK-H
V
BATOK-L
V(BATOK) = 3.6V
I(BATOK) = - 100µA
2.4
83
Min
Typ
95
92
3
1
200
2.85
2.65
0.20
1
200
5
300
µA
mV
5
300
3.0
Max
99
Units
% of
V
OUT-NOM
(Note 10)
µA
mV
V
POK Characteristics
BATOK Characteristics
Note 1:
Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of
the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the
Electrical Characteristics tables.
Note 2:
All voltages are with respect to the potential at the GND pin.
Note 3:
Voltage on the EN pin must not be brought above V
IN
+ 0.3V.
Note 4:
Thermal shutdown circuitry protects the device from permanent damage.
Note 5:
The human-body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin. The machine model is a 200pF capacitor discharged
directly into each pin.
Note 6:
Maximum ambient temperature (T
A-MAX
) is dependent on the maximum operating junction temperature (T
J-MAX-OP
= 125
o
C), the maximum power
dissipation of the device in the application (P
D-MAX
), and the junction-to ambient thermal resistance of the part/package in the application (θ
JA
), as given by the
following equation: T
A-MAX
= T
J-MAX-OP
- (θ
JA
x P
D-MAX
). The ambient temperature operating rating is provided merely for convenience. This part may be operated
outside the listed T
A
rating so long as the junction temperature of the device does not exceed the maximum operating rating of 125
o
C.
Note 7:
Junction-to-ambient thermal resistance is highly dependent on application conditions and PC board layout. In applications where high maximum power
dissipation exists, special care must be paid to thermal dissipation issues. For more information on these topics, please refer to the
Power Dissipation
section of
this datasheet.
Note 8:
All room temperature limits are 100% tested or guaranteed through statistical analysis. All limits at temperature extremes are guaranteed by correlation
using standard Statistical Quality Control methods (SQC). All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are not
guaranteed, but do represent the most likely norm.
Note 9:
C
IN
, C
OUT
, C
1
, and C
2
: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics
Note 10:
V
OUT (NOM)
is the nominal output voltage of the part. An example: V
OUT-NOM
of LM2798MM-1.8 is 1.8V.
Note 11:
Efficiency is measured versus V
IN
, with V
IN
being swept in small increments from 3.0V to 4.2V. The average is calculated from these measurement results.
Weighting to account for battery voltage discharge characteristics (V
BAT
vs. Time) is not done in computing the average.
Note 12:
Turn-on time is measured from when the EN signal is pulled high until the output voltage crosses 90% of its final value. Resistive load used for startup
measurement, with value chosen to give I
OUT
= 100mA when the output voltage is fully established.
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