LTC2908
7
2908fd
TYPICAL PERFORMANCE CHARACTERISTICS
Specifi cations are at T
A
= 25°C unless otherwise noted.
PIN FUNCTIONS
OUTPUT SOURCE CURRENT, I
RST
(μA)
0
RST OUTPUT VOLTAGE HIGH, V
OH
(V)
3
4
–16
2908 G21
2
1
–4
–8
–12
–20
85°C–40°C
5
25°C
V1 = 5.0V
V2 = 3.3V
V3 = 2.5V
V4 = 1.8V
V
ADJ1
= V
ADJ2
= 0.55V
SUPPLY VOLTAGE, V
CC
(V)
1.5
RST PULL-UP CURRENT, I
RST
(μA)
–20
–25
–30
34
2908 G20
–15
–10
2 2.5
3.5 4.5 5
–5
0
V
RT25
LTC2908-C1
V
RT50
LTC2908-A1
V
RT33
LTC2908-B1
V
CC
= V1 = V2 (A1/B1), V
CC
= V1(C1)
V3 = 2.5V (A1)/V3 = 1.8V (B1)
V4 = 1.8V (A1)/V4 = 1.5V (B1)
V
ADJ1
= V
ADJ2
= 0.55V (A1/B1)
V
ADJ1
= V
ADJ2
= V
ADJ3
= V
ADJ4
=
V
ADJ5
= 0.55V(C1)
RST HELD AT 0V
RST Pull-Up Current vs
Supply Voltage
RST Output Voltage High vs
RST Output Source Current
LTC2908-A1
RST OUTPUT VOLTAGE HIGH V
OH
(V)
OUTPUT SOURCE CURRENT, I
RST
(μA)
0
0.5
1.0
1.5
2.0
–1 –2 –3 –4
2908 G24
–5 –6 –7 –8
25°C
85°C
V1 = 2.5V
V
ADJ1
= V
ADJ2
= V
ADJ3
=
V
ADJ4
= V
ADJ5
= 0.55V
–40°C
OUTPUT SOURCE CURRENT, I
RST
(μA)
0
0.5
RST OUTPUT VOLTAGE HIGH, V
OH
(V)
1.0
1.5
2.0
2.5
3.0
–2
–4 –6 –8
2908 G22
–10 –12
85°C
–40°C
25°C
V1 = 3.3V
V2 = 2.5V
V3 = 1.8V
V4 = 1.5V
V
ADJ1
= V
ADJ2
= 0.55V
RST Output Voltage High vs
RST Output Source Current
LTC2908-B1
RST Output Voltage High vs
RST Output Source Current
LTC2908-C1
V2 (Pin 1/Pin 4): Voltage Input 2. The greater of V1, V2 is
also the internal V
CC
. The operating voltage on this pin shall
not exceed 6V. When in normal operation (V1 > V2), this pin
draws approximately 8μA. When this pin is acting as the
V
CC
(V2 > V1), this pin draws an additional 16μA. Bypass
this pin to ground with a 0.1μF (or greater) capacitor.
V4 (Pin 2/Pin 3): Voltage Input 4.
RST (Pin 3/Pin 2): Reset Logic Output. Pulls low when
any voltage input is below the reset threshold and is held
low for 200ms after all voltage inputs are above threshold.
This pin has a weak pull-up to V
CC
and may be pulled above
V
CC
using an external pull-up.
GND (Pin 4/Pin 1): Device Ground.
(TS8 Package/DDB8 Package) LTC2908-A1/LTC2908-B1
V
ADJ2
(Pin 5/Pin 8): Adjustable Voltage Input 2. See Table 1
for recommended ADJ resistors values.
V3 (Pin 6/Pin 7): Voltage Input 3.
V
ADJ1
(Pin 7/Pin 6): Adjustable Voltage Input 1. See Table 1
for recommended ADJ resistors values.
V1 (Pin 8/Pin 5): Voltage Input 1. The greater of V1, V2 is
also the internal V
CC
. The operating voltage on this pin shall
not exceed 6V. When in normal operation (V1 > V2), this pin
draws approximately 26 μA. When this pin is not acting as
the V
CC
(V2 > V1), this pin draws approximately 8μA. Bypass
this pin to ground with a 0.1μF (or greater) capacitor.
Exposed Pad (Pin 9, DDB8 Only): Exposed pad may be
left open or connected to device ground.
