Document
Contents
Features .............................................................. 1 Applications ......................................................... 1 Selection Guide ................................................... 1 Block Diagram ..................................................... 2 Pin Assignment ................................................... 2 Absolute Maximum Ratings ................................. 2 Electrical Characteristics ..................................... 3 Test Circuits ........................................................ 6 Operation Timing Charts (S-8423AFS)................ 7 Operation............................................................. 8 Transient Response ............................................ 10 Standard Circuit................................................... 19 Application Circuits .............................................. 20 Characteristics..................................................... 23 Dimensions, Taping............................................. 35
Rev.2.0
BATTERY BACKUP IC
S-8423 Series
The S-8423 Series is a CMOS IC designed for use in the switching circuits of main and backup power supplies of 3-V or 5-V operation microcomputers. It consists of two voltage regulators, three voltage detectors, a switchover circuit, and a control circuit. In addition to being able to switch from primary to backup power supplies, the S8423 Series has three types of voltage detection output signal corresponding to the power supply voltage. The special sequence for switch control prevents unnecessary exhaustion of the backup power supply; this feature is suitable for structuring backup systems.
n Features
• Low power consumption Normal operation: 43 µA max. (VIN=6 V) Backup: 2.1 µA max. • Voltage requlator Small input/output voltage differences : 0.35 V max. (IOUT=50mA) Output voltage tolerance : ±2% • Three built-in voltage detectors (CS, PREEND, RESET) Detection voltage tolerance: ±2% • Special sequence Backup voltage is not output, if the primary power supply voltage does not reach the RESET voltage that activates a CPU.
n Applications
• Video camera recorder • Still video camera • Memory card • SRAM backup equipment
n Selection Guide
(Ta=25 °C) Model No.** Output voltage*(V) Min. S-8423AFX S-8423NFX S-8423LFX 3.23 3.135 4.90 Typ. 3.30 3.200 5.00 Max. 3.37 3.265 5.10 CS detection voltage(V) Min. 3.919 3.234 4.507 Typ. 4.000 3.300 4.600 Max. 4.081 3.366 4.693 CS release voltage(V) Min. 4.003 3.315 4.609 Typ. 4.100 3.400 4.719 Max. 4.197 3.485 4.828 RESET detection voltage(V) Min. 2.253 2.351 2.253 Typ. 2.300 2.400 2.300 Max. 2.347 2.449 2.347
* VRO=VOUT ** The last digit ”X” of the model No. changes depending upon the package form. ( X=S : 8-pin SSOP, X=T : 8-pin TSSOP )
Seiko Instruments Inc.
1
BATTERY BACKUP IC S-8423 Series
n Block Diagram
VOUT
VIN
M1 REG2
VBAT
CS voltage detector
V SW1 detection circuit
RESET voltage detector
PREEND voltage detector
PREEND
RESET
.