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DS1830/A DS183
DS1830/A Reset Sequence Pushbutton
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FEATURES
5V (DS1830) or 3.3V (DS1830A) power-on reset Excellent for systems that need power-on resets in a consistent sequence Asserts resets during power transients Pushbutton reset input for system override Selectable reset timing Reduces need for discrete components Precision temperature-compensated voltage reference 8-pin DIP, 8-pin SO, or space saving 8-pin SOP Operating temperature of -40C to +85C Open-drain, active-low inputs
PIN ASSIGNMENT
PIN DESCRIPTION
1 PBRST 2 TD 3 TOL 4 GND 8 VCC 7 RST1 6 RST2 5 RST3 - Pushbutton Reset Input - Time Delay Select Input - VCC Tolerance Select Input - Ground - Power Supply - Reset 1 Output - Reset 2 Output - Reset 3 Output
DESCRIPTION
The DS1830 Reset Sequencer monitors the power supply for an in-tolerance condition and the pushbutton reset input for a manual reset. First a precision temperature-compensated reference and comparator circuit monitors the status of the power supply and when an out-of-tolerance condition is detected, an internal power fail signal is generated that forces the reset lines to go to an active state. If the power supply returns to an in-tolerance condition, RST1 will release followed by RST2 and finally RST3 . Sequencing of resets allows for systems to power-up in an orderly manner providing superior reliability.
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, click here: http://dbserv.maximic.com/errata.cfm.
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060303
D1830/A
OPERATION -- POWER MONITOR
The DS1830 provides the functions of detecting out-of-tolerance conditions on a power supply and warning a processor based system of impending power failure. When VCC is detected as out-of-tolerance all reset outputs will be forced active. When VCC returns to a valid state, RST1 will remain active for period of time based on the condition of the TD input. Reset outputs RST2 and RST3 follow RST1 , each one at the proper delays for the condition of the TD input. All resets will remain in the inactive state (high) until the next VCC out-of-tolerance condition or pushbutton reset. On power-up all resets are kept active for an appropriate period determined by the status of the TD input after the power supply inputs have reached the selected tolerance. This allows the power supply and system power to stabilize before the reset sequences are released.
BLOCK DIAGRAM Figure 1
OPERATION -- TOLERANCE SELECT
The DS1830/A provides a TOL input for individual customization of the DS1830x to specific application requirements (see Table 1). For the tolerance selection, see Table 1 below. The TOL input is only sampled while VCC is below the lowest potential trip value and can not be changed after the VCC voltage exceeds the lowest potential trip value.
TOL -- TOLERANCE SELECT Table 1
TOL VCC GND OPEN (N.C.) 5V (DS1830) 5% 10% 15% 3.3V (DS1830A) 5% 10% 20%
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OPERATION -- PUSHBUTTON RESET
The DS1830 provides a pushbutton switch for manual reset control. When any of the DS1830/A resets are not active (low) a reset cycle can be initiated by a pushbutton reset. The pushbutton reset is generated by pulling the PBRST pin low for at least 1ms. When the push- button is held low all resets are forced active. The reset will remain active until the pushbutton input is released and then will start a sequenced time-out based on the condition of the TD input. The Pushbutton input is pulled high through an internal 40kW pull-up resistor and debounced via internal circuitry. See Figure 2 for an application example and Figure 3 for the timing diagram.
PUSHBUTTON RESET Figure 2
TIMING DIAGRAM -- PUSHBUTTON RESET Figure 3
OPERATION -- TIME DELAY SELECT
The DS1830 provides an input to select three time delay characteristics for the reset outputs. The TD input has 3 states high (VCC), low (ground) and no connect (N.C.). Table 2 details the minimum timing based on the state of the TD input. If the TD input is connected to ground; RST1 will have a minimum time delay of 10 ms after VCC is in tolerance. If the TD input is floated; RST1 will have a minimum time delay of 20 ms after VCC is in tolerance. If the TD input is connected to VCC, RST1 will have a minimum time delay of 50 ms after VCC is in tolerance. An oscillator and clock chain generate the reset timing with each time delay based on the same device oscillator. The time delay for RST2 will be 5 times as long as RST1 and RST3 will be 10 times the duration of RST1 .
TD CONTROL MINIMUM RESET TIMING Table 2
TD TD = GND TD = N.C. TD = VCC TRST1 10ms 20ms 50ms TRST2 50ms 100ms 250ms TRST3 100ms 200ms 500ms
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APPLICATION DIAGRAM -- CASCADE DELAY CONFIGURATIONS Figure 4
MASTER
SEE NOTE 2
SEE NOTE 1
SLAVE
SEE NOTE 2
Note 1: The RST3 output tied to the pushbutton reset would be pulled to VCC through the 40kW resistor in the pushbutton input. If a stronger pull-up is required an additional pull-up resistor could be added. Note 2: When using the cascade configuration, it is important that the TOL pins of the master and the slave are configured so that the master's VCCTP is greater than the slave's VCCTP. This will ensure that when the master's higher VCCTP is crossed, the resets will ripple through to the slave.
TIMING DIAGRAM -- POWER-DOWN Figure 5
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TIMING DIAGRAM -- POWER-UP Figure 6
ABSOLUTE MAXIMUM RATINGS*
Voltage on any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature -0.5V to +6.0V -40C to +85C -55C to +125C See IPC/JEDEC J-STD-020A
* This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS (-40C to +85C)
PARAMETER Supply Voltage PBRST Input High Level PBRST Input Low Level SYMBOL VCC VIH VIL MIN 1.0 2.0 -0.3 TYP MAX 5.5 VCC + 0.3 +0.5 UNITS NOTES V 1 V V
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DC ELECTRICAL CHARACTERISTICS (-40C to +85C; VCC = 1.0V to 5.5V)
PARAMETER VCC Trip Point (TOL= VCC) DS1830 VCC Trip Point (TOL=GND) DS1830 VCC Trip Point (TOL=Open) DS1830 VCC Trip Point (TOL= VCC) DS1830A VCC Trip Point (TOL=GND) DS1830A VCC Trip Point (TOL=Open) DS1830A Input Leakage Output Current @ 0.4V Operating Current (Standby) SYMBOL VCCTP VCCTP VCCTP VCCTP VCCTP VCCTP IIL IOL
ICC
DS1830 DS1830A
MIN 4.50 4.25 4.00 2.98 2.80 2.47 -1.0 20
TYP 4.62 4.37 4.13 3.06 2.88 2.55
MAX UNITS NOTES 4.74 4.49 4.24 3.15 2.97 2.64 +1.0 V V
V
V V V A mA A 2 3 4
18 10
35 25
AC ELECTRICAL CHARACTERISTICS (-40C to +85C; VCC = 1.0V to 5.5V)
PARAMETER PBRST = VIL RESET Active Time ( RST1 /TD =GND) RESET Active Time ( RST1 /TD =Float) RESET Active Time ( RST1 /TD = VCC) RESET Active Time ( RST2 ) RESET Active Time ( RST3 ) VCC Detect to RST VCC Slew Rate VCC Detect to RST VCC Slew Rate PBRST Stable Low to RST SYMBOL MIN tPB tPDLY tRST1 tRST1 tRST1 tRST2 tRST3 tRPD tF tRPU tR tPDLY 20
See RESET Active Times
TYP 15 30 75 5x tRST1 10x tRST1 5
MAX UNITS NOTES ms 20 40 100 ms ms ms ms ms 8 s s ms ns ms 5 6 7
10 20 50
0 1.0 1.5 2.0
CAPACITANCE (TA = +25C)
PARAMETER Input Capacitance Output Capacitance SYMBOL MIN CIN COUT TYP MAX UNITS NOTES 5 pF 7 pF
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NOTES:
1. All voltages are referenced to ground. 2. PBRST is internally pulled up to VCC with an internal impedance of 40kW typical. 3. Measured with PBRST = VCC and RST1 , RST2 , and RST3 open. 4. Measured with outputs open and all inputs at VCC or Ground (except TD and TOL can be floating). 5. Noise Immunity - Pulses < 2ms at VCC TP minimum will not cause a reset. 6. The tF value is for reference in defining values for tRPD and should not be considered a requirement for proper operation or use of the device. 7. See tRST1, tRST2, and tRST3 for specific tRPU AC timing parameters.
ORDERING INFORMATION
PART # DS1830 DS1830S DS1830U DS1830A DS1830AS DS1830AU PIN PACKAGE 8-DIP 300-MIL 8-SO 150-MIL 8-SOP 118-MIL 8-DIP 300-MIL 8-SO 150-MIL 8-SOP 118-MIL TEMP -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C TYPE 5V Reset Sequencer 5V Reset Sequencer 5V Reset Sequencer 3.3V Reset Sequencer 3.3V Reset Sequencer 3.3V Reset Sequencer
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