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ASM1834A/D  
Dual 5V and 3.3V μP Power Supply  
Supervisor with Manual Reset  
General Description  
Key Features  
The ASM1834 supervisors simultaneously monitor both  
3.3V and 5V power sources and generate reset signals  
when either supply is out of tolerance. When an out-of-  
tolerance condition is detected, the output-reset signal of  
the affected supply becomes active and resets the  
system microprocessor/microcontroller. On power-up and  
after the supply voltage returns to an in-tolerance  
condition, the reset signal remains active for pproximately  
350ms. This allows the power supply and system  
microprocessor to stabilize.  
Monitors 5V and 3.3V supplies simultaneously  
5V and 3.3V power-on reset  
350ms reset time  
Debounced pushbutton reset input  
Push-pull CMOS output  
ASM1834, ASM1834D  
Eliminates external pull-up resistors  
Active LOW (ASM1834), HIGH (ASM1834D)  
Open Drain Output  
ASM1834A  
Tolerance levels are independently selectable for both  
supplies. Tolerance options are 5% and 10% percent for  
the 5V supply and 10% and 20% percent for the 3.3V  
supply.  
Active LOW  
Selectable 5V and 3.3V trip point tolerance  
Internal power drawn from highest input voltage, 5V  
or 3.3V  
The ASM1834 and ASM1834D have push-pull reset  
output stages. The ASM1834A reset outputs are open  
drain devices that can both be connected to either 5V or  
3.3V supply. The ASM1834 and ASM1834A have active  
LOW reset outputs. The ASM1834D has active HIGH  
reset outputs.  
Precision temperature-compensated voltage  
reference and comparator  
Low cost surface mount SO, compact MicroSO and  
DIP packages.  
Wide operating temperature: -40°C to +85°C  
All devices can generate reset signals through an  
internally debounced pushbutton reset input that affects  
both reset outputs.  
Applications  
Microprocessors  
PDAs, Hand-held PCs  
Embedded Controllers  
Telecommunication Systems  
Power Supplies  
All devices operate over the extended industrial  
temperature range. Devices are available in 8-pin DIP,  
surface mount 8-pin SO and 8-Pin MicroSO packages.  
Die are also available.  
Wireless / Cellular Systems  
Networking Hardware  
©2010 SCILLC. All rights reserved.  
Publication Order Number:  
JANUARY 2010 – Rev. 2  
ASM1834/D  
ASM1834A/D  
Typical Operating Circuit  
Block Diagram  
Rev. 2 | Page 2 of 12 | www.onsemi.com  
ASM1834A/D  
Pin Configuration  
*AS1834D reset outputs are active HIGH (5V RESET and 3.3V RESET) Outputs are open-drain for AS1834A.  
Pin Description  
Pin #  
Pin Name  
Function  
1
5VIN  
5V RESET  
5V RESET  
5V TOL  
GND  
5V power supply input.  
5V reset output (Active LOW, ASM1834, ASM1834A. Open drain outputs for ASM1834A).  
5V reset output (Active HIGH, AS1834D).  
2
3
4
5
5V input tolerance select: 10% tolerance for 5VTOL= 5VIN and 5% tolerance for 5VTOL = GND  
Ground.  
Debounced manual pushbutton reset input (40kΩ internal pull-up).  
PBRST  
3.3V input tolerance select: 20% tolerance for 3.3VTOL = 3.3VIN and 10% tolerance for  
3.3VTOL=GND.  
6
3.3V TOL  
3.3V RESET  
3.3V RESET  
3.3VIN  
3.3V reset output (Active LOW, ASM1834, ASM1834A. Open drain outputs for ASM1834A).  
3.3V reset output (Active HIGH, AS1834D).  
7
8
3.3V power supply input.  
Detailed Description  
Operation Power Monitor  
The ASM1834 supervisors simultaneously detect out-of-  
tolerance power supply conditions on both 3.3V and 5V  
power supplies. If the voltages at 5VIN or 3.3VIN are  
outside the tolerance band, the reset for the falling supply  
voltage becomes active. When the monitored supply  
returns to an intolerance state, the reset remains active  
for approximately 350ms before returning to the inactive  
state.  
On power-up, the reset signals are kept active for  
approximately 350ms after the power supply voltages  
have reached the selected tolerance. This allows the  
power supply and microprocessor to stabilize before the  
reset is removed.  
All supply current for the ASM1834 devices is drawn from  
the input (5VIN or 3.3VIN) with the highest voltage level.  
The outputs draw current from their input supplies 5VIN  
and 3.3VIN.  
Rev. 2 | Page 3 of 12 | www.onsemi.com  
ASM1834A/D  
Reset Signal Polarity and Output Stage Structure  
The ASM1834 and the ASM1834A supervisors have  
active LOW reset signals. The ASM1834D reset outputs  
are active HIGH.  
The ASM1834 and the ASM1834D have CMOS push-pull  
output stages. The ASM1834A has open drain reset  
outputs.  
RESET  
Polarity  
LOW  
Output Stage  
Configuration  
Push-Pull  
Part #  
ASM1834  
ASM1834U  
ASM1834S  
ASM1834A  
ASM1834AU  
ASM1834AS  
ASM1834D  
ASM1834DU  
ASM1834DS  
LOW  
Push-Pull  
LOW  
Push-Pull  
LOW  
Open Drain  
Open Drain  
Open Drain  
Push-Pull  
LOW  
LOW  
HIGH  
HIGH  
HIGH  
Push-Pull  
Push-Pull  
Manual Reset Operation  
Push-button switch input, PBRST, allows the user to  
override the internal trip point detection circuits and issue  
reset signals. The pushbutton input is debounced and is  
pulled HIGH through an internal 40kΩ resistor.  
When at least one of the reset outputs is not asserted, a  
push button initiated reset signal can be issued by  
holding PBRST LOW for at least 2ms. When PBRST is  
held LOW, both resets become active and remain active  
for approximately 350ms after PBRST returns HIGH.  
(See Figures 3 and 4.)  
Rev. 2 | Page 4 of 12 | www.onsemi.com  
ASM1834A/D  
Reset Output Signal  
Reset output signals are valid as long as either voltage at  
5VIN or 3.3VIN is above 1.2V. In addition, the ASM1834  
has push-pull outputs that can remain valid below a 1.2V  
input level. To sink current below 1.2V, a resistor should  
be connected from the RESET output to ground. This  
resistor guarantees a valid reset signal down to 0V. A  
100kΩ value is suggested.  
most applications and a value of 10kΩ is suggested.  
(See Figures 5 and 6.)  
The ASM1834A open drain reset outputs can be  
connected to the same potential through a single pull-up  
resistor. In this configuration a failure on either supply will  
generate an active LOW reset. If the inputs are pulled-up  
to different voltages, the reset outputs (pin 2 and pin 7)  
cannot be connected to form a wired “AND” (see Figure  
7).  
The AS1834A open drain reset outputs require pull-up  
resistors and must be low enough in value to pull the  
output into a HIGH state. Resistor value is not critical in  
Rev. 2 | Page 5 of 12 | www.onsemi.com  
ASM1834A/D  
Trip Point Tolerance Selection  
The 3.3VTOL and 5VTOL inputs allow independent  
selection of the reset trip points. If 5VTOL is connected to  
the 5V supply input, a 10% tolerance is selected. If  
5VTOL is grounded, a 5% tolerance is selected.  
If 3.3VTOL is connected to the 3.3V supply input, a 20%  
tolerance is selected. If 3.3VTOL is grounded, a 10%  
tolerance is selected. (Refer to table below.) The  
3.3VTOL and 5VTOL tolerance select inputs should be  
tied to the ground or to the respective input supply  
voltage pin, 3.3VIN or 5VIN.  
3.3V Input  
Tolerance  
5V Input  
TRIP Point (V)  
NOM  
TRIP Point (V)  
NOM  
3.3V  
5V  
Tolerance  
10%  
Select  
Tolerance  
MIN  
MAX  
MIN  
4.25  
4.5  
MAX  
4.49  
4.75  
5VTOL = 5VIN  
5VTOL = GND  
3.3VTOL = 3.3VIN  
3.3VTOL = GND  
4.38  
5%  
4.63  
20%  
10%  
2.47  
2.80  
2.55  
2.88  
2.64  
2.97  
Rev. 2 | Page 6 of 12 | www.onsemi.com  
ASM1834A/D  
Absolute Maximum Ratings1  
Parameter  
Min  
-0.5  
-0.5  
-0.5  
Max  
Unit  
V
2
Voltage on VCC  
7
Voltage on 5V RESET2  
Voltage on 3.3V RESET2  
+5VIN + 0.5V  
V
+3.3VIN + 0.5V  
V
Voltage on PBRST and reset outputs2  
(+5VIN + 0.5V) or (+3.3VIN + 0.5V)  
-0.5  
-40  
V
whichever is greater  
Operating Temperature Range  
Soldering Temperature (for 10 sec)  
Storage Temperature  
+85  
+260  
+125  
2
°C  
°C  
°C  
KV  
V
-55  
HBM  
ESD rating  
MM  
200  
Note: 1. These are stress ratings only and functional implication is not implied. Exposure to absolute maximum ratings for extended periods may affect  
device reliability.  
2. Voltages are measured with respect to ground.  
Recommended DC Operating Conditions  
Recommended DC operating condition over the operating temperature range of -40°C to +85°C. All voltages are referenced to ground.  
Parameter  
Symbol  
5VIN  
3.3VIN  
VIH  
Conditions  
Min  
1.2  
Typ  
Max  
5.5  
Unit  
V
5V Supply Voltage  
3.3V Supply Voltage  
PBRST Input High Level  
PBRST Input High Level  
PBRST Input Low Level  
1.2  
5.5  
V
2
VINMAX + 0.3  
V
VIH  
Both 3.3VIN and 5VIN ≥ 2.7V  
Both 3.3VIN and 5VIN ≤ 2.7V  
VINMAX - 0.4  
-0.3  
V
VIL  
0.5  
V
Rev. 2 | Page 7 of 12 | www.onsemi.com  
ASM1834A/D  
DC Electrical Characteristics  
Unless otherwise noted, VIN = 1.2V to 5.5V and specifications are over the operating temperature range of -40°C to +85°C. (Note: 3.3VIN is always ≤ 5VIN)  
Parameter  
Symbol  
Conditions  
Min  
Typ  
Max  
Unit  
Output = 2.4V. Either 3.3VIN  
or 5.5VIN ≥ 2.7V  
Output Current  
IOH  
350  
μA  
(ASM1834/1834D only)  
Output = 0.4V. Either 3.3VIN  
or 5.5VIN ≥ 2.7V  
Output Current  
IOL  
10  
mA  
(ASM1834/1834D only)  
Output Voltage  
Input Leakage  
VOH  
IIL  
VIN - 0.1V  
V
-1.0  
+1.0  
30  
μA  
3.3VIN and 5VIN≤ 5.5V,  
RESET outputs open.  
3.3VIN and 5VIN≤ 3.6V,  
RESET outputs open.  
5VTOL = GND  
5V Operating Current  
3.3V Operating Current  
ICC  
16  
12  
μA  
μA  
ICC  
25  
5V Trip Point  
VINTP  
VINTP  
VINTP  
VINTP  
COUT  
4.50  
4.25  
2.80  
2.47  
4.63  
4.38  
2.88  
2.55  
4.75  
4.49  
2.97  
2.64  
10  
V
V
5V Trip Point  
5VTOL = 5VIN  
3.3V Trip Point  
3.3V Trip Point  
Output Capacitance  
3.3VTOL = GND  
V
3.3VTOL = 3.3VIN  
V
pF  
PBRST Manual Reset  
Minimum Low Time  
tPB  
2
ms  
ms  
PBRST Stable LOW to  
reset Active  
tPDLY  
2
Reset Active Time  
VCC Slew Rate  
tRST  
tF  
200  
300  
0
350  
350  
500  
ms  
μs  
ns  
VINTP(MAX) to VINTP(MIN)  
VINTP(MIN) to VINTP(MAX)  
VCC Slew Rate  
tR  
VCC Detect to RESET  
or RESET  
tRPU  
trise = 5μs  
200  
500  
2
ms  
VCC Detect Noise  
Immunity  
tRPD  
μs  
Rev. 2 | Page 8 of 12 | www.onsemi.com  
ASM1834A/D  
Package Information  
MicroSO (8-Pin)  
Rev. 2 | Page 9 of 12 | www.onsemi.com  
ASM1834A/D  
Rev. 2 | Page 10 of 12 | www.onsemi.com  
ASM1834A/D  
Ordering Information  
Note: For parts to be packed in Tape and Reel, add “-T” at the end of the part number.  
Rev. 2 | Page 11 of 12 | www.onsemi.com  
ASM1834A/D  
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