Manual

MAX847
1-Cell, Step-Up
Two-Way Pager System IC
8 _______________________________________________________________________________________
LBO
LBI
CH0
0.6V
CH0
RUN/
COAST
OV0–OV4
SERIAL
I/O
CH1
CH2CP2
CP1
CP0
S1
7
DAC0–DAC7
RESET
CONTROL
V FEEDBACK
CHARGE
NICD
OR
BACKUP
REGULATOR
PWM
(PFM IN
COAST)
CHG/REG
+
–
CP
LB
N
6
11
25 27
SDOSDISCL
3 26
9
REF
0.6V
1µF
10µA
3.3V
1.0V
REG3
1µF
8
RSIN
10
17 18 19 16 15
20
21
14
DR1 DR2IN DR2
DRGND
N
1.8Ω
1.8Ω
REG2 ON
REG3 ON
N N
P
P
N
P
7
+
–
+
–
+
–
FROM
NICD
FROM
BATTERY
7-BIT
CH
DAC
5
5
REG2
REG1
R2IN
C
OFS
0.1µF
OFS
NICD
R
OFS
15k
10µF
10µF
OUT
SYNC
FILT
PGND
LX1
BATT
1-CELL
BATTERY IN
L1
22µH
22µF
47µF
+
–
A
OUT
+
–
CP
RS
CS
28
RUN
1.28V
REFERENCE
1.0V
+
–
A
R3
BACKUP
REGULATOR
CLAMP ON WHEN
OV4 = 1
3.3V
CLAMP
1mA/
15mA
CHARGE
P
+
–
A
R2
+
–
A
R1
AGND
22
23
24
25
13
1nF 22nF
10k
12
4
1
x7
PLL
LBO
RSO
MAX847
Figure 1. Functional Diagram