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http://www.union-ic.com Rev.04 Feb.2014

9/12

UM2002

Application operating conditions

Refer to Figure 4

Symbol

Parameter

Conditions

Min

Typ

(Note 8)

Max

Unit

Reference Bias Voltage (B)

2.1

5

V

Input Voltage on pin EN

2.1

5

V

Reference Voltage (A)

0

1.5

4.4

V

Pass Switch Current

14

mA

Reference Current

Transistor

5

μA

Ambient Temperature

Operating

in

free-air

-40

+85

°C

Sizing pull-up resistor

The pull-up resistor value needs to limit the current through the pass transistor when it is in the

ON state to about 15mA. This ensures a pass voltage of 260mV to 350mV. If the current through

the pass transistor is higher than 15mA, the pass voltage also is higher in the ON state. To set the

current through each pass transistor at 15mA, the pull-up resistor value is calculated as:

A

V

V

R

D

pu

PU

015

.

0

35

.

0

)

(





The table below summarizes resistor reference voltages and currents at 15mA, 10mA, and 3mA.

The resistor values shown in the +10 % column or a larger value should be used to ensure that the

pass voltage of the transistor would be 350 mV or less. The external driver must be able to sink

the total current from the resistors on both sides of the UM2002 device at 0.175V, although the

15mA only applies to current flowing through the UM2002 device.

Pull-up resistor values

Pull-up resistor value (Ω)

15mA

10mA

3mA

Nominal

+10 %

(Note 9)

Nominal

+10 %

(Note 9)

Nominal

+10 %

(Note 9)

5V

310

341

465

512

1550

1705

3.3V

197

217

295

325

983

1082

2.5V

143

158

215

237

717

788

1.8V

97

106

145

160

483

532

1.5V

77

85

115

127

383

422

1.2V

57

63

85

94

283

312