SLUS508A – DECEMBER 2001 REVISED – JUNE 2002
FEATURES
Detachable Unit Allowing Replacement
Integrated 6-pF Watch Crystal for Real-Time
DESCRIPTION
Clock Operation
Integrated Lithium Coin Cell for Nonvolatile
Memory Backup
Protects Battery and Crystal From Conditions
Associated with Surface Mount Soldering
For Use With bq4802YDSH and bq4802LYDSH
Keyed Insertion to Avoid Incorrect Attachment
The bq48SH–28x6 is the top section suitable for any
SOIC (DSH) packaged IC including the bq4802YDSH
or bq4802LYDSH parallel real-time clock (RTC) and
NVSRAM controller.
The fully integrated SNAPHAT includes a 6-pF watch
crystal and lithium coin cell with 48 mAh of capacity.
The SNAPHAT is designed to be attached after the
DSH packaged base SOIC has been soldered
preventing the battery and crystal being over-stressed
by the soldering temperatures.
APPLICATIONS
Telecommunications Base Stations
Servers
Handheld Data Collection Equipment
AVAILABLE OPTIONS
TA
PACKAGED DEVICES
SNAPHAT (NSH)
SYMBOL
0°C to 70°C
bq48SH–28x6NSH
bq48SH–28x6
† The SNAPHAT package is available taped and
reeled. Add an R suffix to the device type (e.g.
bq48SH–28x6NSHR to order quantities of 2,500
devices per reel.
CONNECTION DIAGRAMS
X2
BC
X1
VSS
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
SNAPHAT is a trademark of STMicroelectronics.
Copyright 2002, Texas Instruments Incorporated
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1
SLUS508A – DECEMBER 2001 REVISED – JUNE 2002
absolute maximum ratings over operating free-air temperature (unless otherwise noted)†
Operating temperature range, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 70°C
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to 85°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C
† Stresses beyond those listed under “absolute maximum ratings” 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 under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
recommended operating conditions
TYP
UNIT
Nominal battery voltage, VCC
2.8
V
Nominal battery capacity
48
mAh
MAX
UNIT
crystal specifications (DT–35 or equivalent)
PARAMETER
TEST CONDITIONS
MIN
TYP
fO
CL
Oscillation frequency
TP
k
Temperature turnover point
Q
Quality factor
R1
Series resistance
45
kΩ
CO
Shunt capacitance
1.1
1.8
pF
CO/C1
Capacitance ratio
430
600
DL
Drive level
∆f/fO
Aging (first year at 25C)
Load capacitance
20
kHz
6
pF
25
Parabolic curvature constant
40,000
NO.
C
70,000
1
1
TERMINAL
NAME
30
–0.042 ppm/C
TERMINAL FUNCTIONS
I/O
DESCRIPTION
BC
3
O
Battery positive terminal
VSS
2
I
Battery negative terminal
X1
1
I
Crystal input
X2
4
O
Crystal output
2
32.768
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µW
ppm
SLUS508A – DECEMBER 2001 REVISED – JUNE 2002
functional description
connections
The SOIC (DSH) is connected to the SNAPHAT containing the battery and crystal through four pins that insert
into four press-fitted sockets in the SOIC (DSH) where the contact area is gold platted. Each of the sockets
internally contains six independent contacts to ensure solid reliable connectivity and minimize contact
resistance.
Four molded retaining clips on the SNAPHAT also help fasten the SOIC (DSH), ensuring mechanical and
electrical connection even under severe mechanical shock and vibration. The combined SOIC (DSH) and
SNAPHAT assembly can sustain shock levels in excess of 100 g without separating. This package also passes
variable frequency testing in accordance with MIL–STD–883, method 2007.2, condition A.
Force – lbs
Figure 1 illustrates the effect of repeated insertion and extraction of the SNAPHAT top to the SOIC (DSH). The
force required to extract the SNAPHAT, and then to re-insert it, reduces each time. After three or four
extractions, though, the reduction starts to become unnoticeable, and the force required remains at a fairly
constant figure. Typically, though, the SNAPHAT needs to be extracted and re-inserted only once in its lifetime.
Figure 1. SNAPHAT Insertion and Extraction Forces
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3
SLUS508A – DECEMBER 2001 REVISED – JUNE 2002
functional description (continued)
battery characteristics
Figure 2 illustrates the lithium coin cell discharge rate for a given load. This demonstrates the characteristically
flat voltage level supplied by the battery until very near the end of its life. These discharge levels have been
greatly accelerated in comparison to the normal, actual usage.
UL recognition
The bq48SH–28x6 has been recognized by Underwriters Laboratories under their Component Recognition
Program and carries UL File No. E89556.
battery life
The life expectancy of the battery is greatly affected by temperature and usage profiles. Figure 2 highlights the
effective discharge during loading periods, but temperature during loading periods can greatly affect the
effective run time as shown in Figure 3.
general notes
To remove the SNAPHAT top for replacement, a DIP/IC extractor tool should be used. The SNAPHAP top
should be grasped by the narrow end to avoid bending the pins.
CAUTION:
To avoid draining the battery, do NOT place SNAPHAT pins into conductive foam.
TYPICAL CHARACTERISTICS
BR1225 LITHIUM COIN CELL DISCHARGE RATE
vs
CELL VOLTAGE
3.5
TA = 20C
VCC – Cell Voltage – V
3.0
2.5
2.0
RL = 30 kΩ
RL = 15 kΩ
1.5
RL = 100 kΩ
1.0
0
400
800
1200
1600
tD – Discharge Duration – h
Figure 2
4
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2000
SLUS508A – DECEMBER 2001 REVISED – JUNE 2002
MECHANICAL DATA
NSH (R-PDIP-P4)
PLASTIC DUAL-IN-LINE
D
Dimension
E
Inches
Millimeters
Min.
Max.
Min.
Max.
A
–
0.385
–
9.78
A1
0.265
0.285
6.73
7.24
A2
0.255
0.275
6.48
6.99
A3
–
0.015
–
0.38
B
0.018
0.022
0.46
0.56
D
0.835
0.860
21.21
21.84
E
0.560
0.590
14.22
14.99
eA
eB
0.612
0.628
15.95
0.126
0.142
15.54
3.20
L
0.080
0.090
2.03
2.29
3.61
A2
A1
A3
A
B
L
eA
eB
4201973/A 08/01
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
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5
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